Technical Analysis: WRC Cars 2017

[dimviii]

Thanks dimviii, just from curiosity point of view - do we know this for certain (about the mechanical front diff on the current WRC cars) and if yes, one more question – how do we know this :)?

they cant use something else,they have to use mechanical diffs,as they are not allowed active diffs, at front/rear.

[NickRally]

they cant use something else,they have to use mechanical diffs,as they are not allowed active diffs, at front/rear.

Hm, I went through the tech rules and couldn’t see a restriction in terms of the operation (i.e. mechanical/hydraulic) of the front and rear diffs.

[J_n_z]

@ dimviii: I know that f.& r. diff are not active and almost certainly have a mechanical locking system...
By (locked diff.) I ment somehow functional mechanical LSD that probably perform quite a good lock at full throttle.

I my thinking is based on Ogiers RWD statement... but I don't know all details that was said, so it may be that I am completely wrong.

PS. As far as I can understand Focus RS system can simulate centre an rear active diff. quite good, but not for very long time of real pushing.

[Mirek]

Anybody know the list of all devices that use hydraulics in the current, 2017, WRC cars?

Gearbox, center differential and handbrake (different circuit I think).


Hm, I went through the tech rules and couldn’t see a restriction in terms of the operation (i.e. mechanical/hydraulic) of the front and rear diffs.

Frankly I haven't chacked the rules myself but afaik all the official announcements before the introduction of 2017 cars were only about center differential.

[Ctesibios]

Mirek, gearbox hydraulics are for shifting only? I am guessing for the center diff it's for the"actuators" however they are made according to each manufacturer. And for the handbrake, is it for disengaging the rear wheels from the drivetrain or some kind of power assist?

[Kris82]

dimvii is right these new cars have mechanical front and rear limited slip differentials (same as the 2011-2016 spec). Mechanical meaning that their state changes mechanically while accelerating, breaking and coasting, although preload is what determines their behavior while coasting. The only differential controlled by a computer via a hydraulic system is the center differential, hence its name "active".


Mirek, gearbox hydraulics are for shifting only? I am guessing for the center diff it's for the"actuators" however they are made according to each manufacturer. And for the handbrake, is it for disengaging the rear wheels from the drivetrain or some kind of power assist?

I don't think there is a rear wheel disconnect on these new models. While a lack of a center diff warranted a use of a clutch pack disconnecting the rear axle to allow handbrake use, the cars with an active center diff. set the differential to an open position while the handbrake is used allowing for both front and rear axles to move independently.

[NickRally]

Agreed with all the statements about the active centre and passive front and rear diffs, just wondering how FIA controls this, but as it isn't in the main rules (or maybe I have missed it), it must be through one of the numerous Technical Directives that get distributed among the competitors, but are not publicly available.

[NickRally]

4. Citroen C3

Time for the last remaining team. I have to say before the season started, I, as many other people, thought this is the car to beat and dominate the championship. After four rallies, we can (luckily) say that this is not quite the case, with all four cars capable of winning and keeping us entertained. At the same time, I am still very impressed with the attention to detail in the C3. After four rallies, if I didn’t know any better, I would have said they have the most mature design overall without necessarily excelling in any one particular area.

Below are few images with notes.

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_1.jpg

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_2.jpg

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_3.jpg

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_4.jpg

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_5.jpg

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_6.jpg

[Mirek]

Nick, what is the effect of the air flow hitting the rotating wheel? I mean with a difusor ahead of the wheel the air coming on the wheel is slower and differently spread than without it. I don't know anything about this phenomena. Is it even being considered in the design of these small difusors?

[NickRally]

That's a very good question Mirek, I will sit down and write something next week (busy weekend).

[jparker]

Very well explained article about Active Central Diffs.
https://www.full-race.com/store/drivetrain/acd-pro-ets-pro-center-diff-controller/acd-pro-mitsubishi-lancer-evolution-active-center-differential-controller-1.html/

[NickRally]

Thanks jparker - interesting reference in the link above about Nissan’s and Subaru’s differential systems.

Also while browsing the net for WRC transmission information, I stumbled across this not very new link, which I am sure it must have already been posted around here, but I will do it for reference, containing interesting info about the diff settings of the previous generation active diff cars:

http://wrcbehindthestages.blogspot.co.uk/2011/05/chapter-15-differential-extravaganza.html

Also pondering few points about differentials below:

1. WRC cars up to and including 2016 – no centre diff, i.e. spool – the rules read:

Front/central/rear differentials
Only the housings and mechanical limited slip differentials
homologated in the WRC extension may be used (without any
modification).
"Mechanical limited slip differential" means any system which
works purely mechanically, i.e. without the help of a hydraulic or
electric system.
A viscous clutch is not considered to be a mechanical system.
Any differential with electronic management is prohibited. The
number and the type of the plates are free.

The significance is that the rules specifically mention mechanically locking central differentials as being allowed, but the common knowledge suggests they were not utilised, i.e. the competitors decided it is better to have a spool (locked front and rear transmission paths) rather than mechanically locking central differential.

2. Torque split of a spool often given as 50:50 – to state the obvious, this is of course seldom correct. It might apply for near perfect conditions where all the gearing is the same, tyre dynamic dia’s are identical and none of the tyres are slipping, otherwise greater proportion of the torque will flow towards the axle/wheel with greater grip/resistance.

3. I was thinking how would I approach the challenge if I was given the task of designing an independent clutch packs type central diff, what would it take? And then I thought the chances for this working on a current rally car are probably greater than implementing it on a road car. A current rally car has got to cover, let’s say, 350 competitive km per event, which is equal or less than F1 race + Qualy + FP3, which in turn is what the transmission there has got to cover in a race weekend – now, before anybody objects saying the transmission stresses in F1 are lower, I am pretty confident it will be the opposite due to the higher engine power coupled with the enormous downforce levels - the stresses on a F1 differential would be higher than WRC car central differential (which also does not see all the gearing of the complete WRC car transmission). With that in mind, in my opinion, to design a reliable independent clutch packs only central diff, will take proper sizing and material selection for the discs as well as sufficient cooling and top that up with plenty of hours on the transmission dyno and the test course. It is maybe unlikely that current WRC teams’ budgets stretch that much, but it is good to dream.

4. Continuing from point 3 above, I suspect the biggest hurdle in making an independent clutch packs central differential work is the actual control strategy – in what manner do you actually use such device. There is a lot of experience in making hydraulically operated epicyclic diff work, but hardly any when it comes to making the clutch packs one working. I suspect the number of options going from the normal hydraulic epicyclic diff to the clutch pack one will increase exponentially. So although the clutch packs will give you way more opportunities, they will be easier to become lost in what you are doing, which means the epicyclic diff will be much easier to work with.

[NickRally]

Continuing my “rant” about differentials, I had a chat with one of my colleagues at work (he is a very common sense person) and after some discussion, we thought the most likely reason for Ogier’s complaints that he ended up with a rear wheel drive car after the hydraulic issues is that the Fiesta had an asymmetric central epicyclic diff, which when in its free state sends more torque to the rear than the front (which of course is not uncommon). As the locking system fails, it will give the driver the feeling of reduced front traction/stability and, talking from experience, very often that would be enough for a driver to proclaim “no front traction at all” or “rear wheel drive only”, although in my field of activity that would sound more like “terrible, no front grip whatsoever” or “horrific, no rear grip at all”, even though the reduction in front or rear grip is actually a very small amount.

[Mirek]

Nick, the pre-2017 WRC rules are basically nothing more than slightly modified S2000 rules. Those were introduced around 2005. The very first S2000 actually had clutchpack-type center differential (Toyota Corolla (RSA), VW Polo (RSA) and Fiat Punto). Peugeot in 2007 was the first one to bring transmission without center diff at all. I believe these were the main reason why not to use it:
- for naturally aspirated S2000 engine the power lost in the center diff was not negligible
- such simple clutchpack brought no significant advantage in handling performance over the variant without center diff at all
- it was an additional weight; in that time the weight limit for S2000 cars was 1100 kg and I know from Barum scrutineering that the limit was totally not achievable with the given rules; i.e. the less weight the better

All other following cars had no center diff at all even though for example Škoda used both variants in testing for comparison. Later even Fiat changed transmission in the Punto for one without center diff.

Honestly I thought that starting with the new WRC rules (2011) the center diff was explicitly banned.

[NickRally]

Thanks for the additional info Mirek, these reasons make sense.

[OldF]

In the past a centre diff with asymmetric torque split was in use. The example is from “few” :) years back in the 1986 Portugal rally which had both tarmac and gravel stages.
The Lancias had a front/rear torque split 25/75 on gravel and 30/70 on tarmac.
The torque split for the Audis was 40/60 all the time.
Malcom Wilson had with the MG Metro a torque split of 35/65 on tarmac and 45/55 on gravel. The other Metro drivers had 25/75 on tarmac and 35/65 on gravel.
The Fords had a torque of split 37/63 all the time.

The active front and rear diffs was banned from the beginning of 2006. If I recall correctly there was also talk about banning the active central diff but at least the drivers wanted to preserve it because it enabled the use of the handbrake. https://en.wikipedia.org/wiki/World_Rally_Car

The rule changes from season to season can be followed on http://juwra.com/seasons.html
The ban of the front and rear diffs is not on Juwra’s 2006 rule changes http://juwra.com/rules_2006.html
Jonkka must have missed it for some reason.

All the manufacturers attending the 1995 wrc season had an active centre diff by the end of the year.

[OldF]

I was thinking how would I approach the challenge if I was given the task of designing an independent clutch packs type central diff, what would it take?

If you mean an independent clutch pack for both front and rear at least the other one have to be normally locked and released by the hydraulic system.

[OldF]

Basics of diffusers.

http://www.racecar-engineering.com/technology-explained/diffusers-engineering-basics-aerodynamics/

[Mirek]

The Fords had a torque of split 37/63 all the time.

I believe the RS200 could have been run as RWD only and such configuration was used on asphalt stages. 4WD of that time were rather clumsy on asphalt especially due to very bad turning ratio (caused by angular limitation of driveshaft joints I believe) combined with no rear axle releasing mechanism. I may be wrong though, I don't remember it very well.

By the way C4 WRC also did not have even torque split. Asphalt center diff was 40/60 if I recall. That was often mentioned as a reason why the car was tricky for privateers and gentleman drivers in the later years and why many used gravel center differential even on asphalt.

This article states that Escort gr.A (prior active diff) could have 30/70 torque settings as well: http://tech-racingcars.wikidot.com/ford-escort-mk-v-rs-cosworth

There are some interesting links inside but they open in Greek language. I don't know if it's possible to switch them in English somehow.


The active front and rear diffs was banned from the beginning of 2006. If I recall correctly there was also talk about banning the active central diff but at least the drivers wanted to preserve it because it enabled the use of the handbrake.

Development of S2000 cars started around 2004-2005 and those were equiped by the simple hydraulic clutch to release the rear axle with handbrake therefore the solution of the issue was probably already known. I believe the real reason was that people were sane enough not to design all new gearbox, center diff and rear axle releasing mechanism in the name of cost saving.

[NickRally]

OK, let’s attempt to answer Mirek’s question on the tunnels/Venturis ahead of the wheels. In open wheel racing, traditionally a wing or a tunnel ahead of a wheel does two main things – first of course it retains its main function of creating downforce and second, by placing it ahead of the wheel, in effect it partially masks the wheel reducing its drag or more appropriately the drag of the overall wing/tunnel and wheel system is less when compared to the wing/tunnel and wheel on their own. This gives slightly better lift to drag ratio.
It is important to mention that wing on its own in free air, both upstream and downstream, will create slightly more lift/downforce for the same angle of incidence than when placed ahead of a wheel, but the combination of a wing ahead of a wheel appears to create a very good overall lift to drag number, i.e. more efficient system overall.
Now, switching to closed wheel cars, there are other dimensions to consider – the air from the tunnel (I will switch to talking about tunnels only as this is the predominant option on a closed wheel car) must be allowed to go somewhere, otherwise imagine if you place a flat plate at the back of the tunnel and block it, it will simply stop working, and as such the wheel arch provides a nice open-ish space for this. There might be better areas to expel the tunnel air, but the rules rarely allow much freedom for tunnel exits in close wheel racing. Expelling the tunnel air in the wheel arch, in turn, can benefit massively from providing good air evacuation from the wheel arch itself usually using louvers on the outside of the arch and of course through the large natural opening on the side of the wheel.
The best example of front tunnels are the current WEC sports prototypes, which are allowed to exit the air from the large front diffusers behind the front wheels in a very well faired and channelled manner.
Going back to the current generation of WRC cars, from the ones that so far appear to have tunnels at the front, Toyota and Citroen, the Toyota’s appear just inside of the wheels, but I need to revisit the images to see where they expel the air, while the Citroen’s are possibly just inside the front wheels but expelling the air in the wheel wells with nice louvers on top of the arches.
One think that I am not sure is how a front tunnel works in combination with a front splitter vertical skirt, which is present on all current generation WRC cars.

[janvanvurpa]

In the past a centre diff with asymmetric torque split was in use. The example is from “few” :) years back in the 1986 Portugal rally which had both tarmac and gravel stages.
The Lancias had a front/rear torque split 25/75 on gravel and 30/70 on tarmac.
The torque split for the Audis was 40/60 all the time.
Malcom Wilson had with the MG Metro a torque split of 35/65 on tarmac and 45/55 on gravel. The other Metro drivers had 25/75 on tarmac and 35/65 on gravel.
The Fords had a torque of split 37/63 all the time.

The active front and rear diffs was banned from the beginning of 2006. If I recall correctly there was also talk about banning the active central diff but at least the drivers wanted to preserve it because it enabled the use of the handbrake. https://en.wikipedia.org/wiki/World_Rally_Car

The rule changes from season to season can be followed on http://juwra.com/seasons.html
The ban of the front and rear diffs is not on Juwra’s 2006 rule changes http://juwra.com/rules_2006.html
Jonkka must have missed it for some reason.

All the manufacturers attending the 1995 wrc season had an active centre diff by the end of the year.

Even looking at the era I like the best, the Group A days between say 88 to 94 its seems that everybody just made all the diff stiffer than hell..Front , center, rear, crazy stiff.. Now add wide tires and tight narrow tarmac roads and you have a car horrible to try and do tight corners...

There there was toque split on those cars...who know but I DO know that many in the Sierra/Sapphire/Escort Cossies did go to 50/50 and to quote one multiple BTRDA Gold Star winner, Pete Doughty, "It handled like a pig, like the old Quattros but 50/50 was the fastest so that is what you run"

[dimviii]

Jerónimo Aliaga‏*@jerowrc
Diferencias aerodinamicas ente @TOYOTA_GR y @HMSGOfficial en la previa del #WRC #RallyArgentina2017

https://pbs.twimg.com/media/C-WJyrmXcAAFyZx.jpg
https://pbs.twimg.com/media/C-WJyr_XoAAU4LB.jpg
https://pbs.twimg.com/media/C-WJyrqXUAgPczV.jpg
https://pbs.twimg.com/media/C-WJyrpWAAAhaZS.jpg

[mknight]

Well I can see the Toyota "pods" are wider at the bottom, but can't see any change to Hyundai at first sight.

[NickRally]

Watching the redbull.tv rally Argentina day 1 recap where, as usual, they start by talking about the previous rally, Corsica in this case, and at 3:23-3:33min from the start of the program Ogier talks about his problems, though I don't know what day of the rally that applies for (I am yet to watch the wrc+ daily highlights from Corsica) - anyway, when talking about his problems he says "diff was locked" and "no hand brake". The significance of this is that if the issue was lost hydraulic pressure, then it means the diff is normally locked when no hydraulic pressure is applied to it. This is possible though I haven't got experience with such arrangement. I am more familiar with the usual normally non-locked diffs that need hydraulic pressure to lock them.
In my view though, it is more likely that they use the normally unlocked diff and the problem would have been in the control electronics, that must have necessitated to manually force the system into a locked state or the control mechanism reverts by default to locked diff state when issues are encountered. The locked diff would then of course explain the lack of hand brake.
The issue above would be the exact opposite of having rear wheel drive only car, but there might have been different problems each day, though the handling of the car from the first Sunday stage on TV appeared to match a car with locked centre diff and no hand brake (overshooting hairpins).

[NickRally]

And now Ostberg - no centre diff and no hand brake

[Mrpengski]

Hey NickRally, I enjoy reading your analysis on aero, it's always good to hear an outside opinion :) Keep it coming!

I think every team did well to hide the extra girth required for the new side impact regulation. Only when you see one from this angle that you realise they are basically pushed out to the regulation width at the waist.
1325

[fecksfx]

Very interesting to read through and try to follow.
Watching the WRC show with a couple of rear diffusers being lost in water splashes, the footage showed it as a significant loss of rear traction with spins in tight corners. Is the down force at slower speeds really likely to be that affected or is that just the footage that was available?

Sorry for the poor grammar, hopefully it makes sense.

[NickRally]

Thanks Mrpengski, I absolutely love the appearance of these new cars.

Hi fecksfx – I doubt the contribution of the rear diffuser to rear/overall grip at low speeds is significant enough to be the cause of the spins you mention. Let’s make an estimate (probably way too optimistic) for the total downforce in gravel trim as 200kg at 150kph and let’s say the contribution of the diffuser to this number is 30 percent (again probably way too optimistic considering the gravel trim ride heights) - this would represent 60kg at 150kph. Now if we reduce the speed down to say 50kph, then the contribution of the rear diffuser will be [(50/150)^2]*60 which is 6.67kg – figure low enough to be lost in the overall noise of the “experiment”. If you add to this that the cars will be very much sideways in such corners (i.e. significant yaw angle), then the contribution of all aero devices will drop even further, though some teams appear to have paid more attention to downforce creation in yaw than other teams. And to add even further point here, the Fiesta diffuser appears to be the most benign of the lot, which means if lost will have less of an effect on downforce. All three other teams have more aggressive diffusers and I suspect they will feel it a bit more if they lose it, but again not at these low speeds. Nevertheless the Fiesta diffuser attachments appear to be a bit fragile with all these instances of broken ones – I am sure the M-Sport guys will be discussing how to improve the attachments in their faults meetings.
I suspect the most significant part that a missing diffuser plays, is in the head of the driver, which in itself is of course a problem.

[Lundefaret]

Hey NickRally, I enjoy reading your analysis on aero, it's always good to hear an outside opinion :) Keep it coming!

I think every team did well to hide the extra girth required for the new side impact regulation. Only when you see one from this angle that you realise they are basically pushed out to the regulation width at the waist.
1325


This is actually the most important change of the 17 rally cars, and also the most road car relevant. It should actually be used in road cars as soon as possible, because as it is for a rally car, side impact is the weakest link also for road cars.

[Mirek]

I don't think that such large safety side zones are realistically possible for road cars. It would add a lot of cost and reduce practical use (or internal space). For example imagine that You add 100 mm on door thickness. Now You park at a mall. Your car is wider, i.e. You have less space around and moreover You need to open the door 100 mm more to be able to get outside. My car is not that big (Octavia III) but very often I can barely get out of it when parking in the city. Another problematic thing is that especially for women the wider and heavier door would be likely difficult to manipulate (especially when You don't park on a leveled ground but on the slope), maybe they would require electric motors, i.e. more cost and more potential issues after crashes.

[Mrpengski]

Nick, who do you figure did the best homework as far as optimising for yaw condition, and why? Also, it was mentioned earlier that most of the details for WRC technical regulation is under 400/01 which is not publicly available. I never realised this, and find it rather annoying, because I enjoy reading other regs (e.g. LM P1, LM GT) when I'm not neck-deep in 400/01, which give full description of legality zones (among others), and are openly available on the FIA website. To comment on your earlier post about underbody treatment, check section 902 of article 255a (the public release). Basically, it doesn't say much, and certainly some take a more liberal approach than others with regards to treating it as an aero device.

Re: diffusers. Without disclosing any numbers or commenting on Nick's estimates ;), I tend to agree that the physical effect of losing the diffuser would be only a small shift in aero balance, but enough to disturb the driver's confidence, which is far more important than a few kilos of downforce. So, as Nick said, some real effects, but mostly what's in the head.

Re: doors. Don't forget that these doors are first gutted out (OEM side impact beam and all) then filled back with energy-absorbing foam. Of course, the OEM beam is replaced by the roll cage, but this is not realistic for a road car, and neither is filling the entire door + outer extension with foam. Among other things, the window won't go down! Incidentally, in my previous job I was involved in a lightweight electric car project with composite monocoque and bodywork. Inside the door was a CFRP side impact beam which housed an outside-firing airbag. I believe it was for pedestrian protection more than occupant protection, but interesting nonetheless. So maybe something like this could be applied to road cars, before we see extra thick rally-style doors.

My earlier comment about the looks of the cars with the side impact is perhaps best appreciated in the context that the regulation of the side impact was finalised rather late for the '17 cars (Article 255a says 10/03/2017 for the official publication date for the side impact :rolleyes:). That's why most "stage 1" test cars didn't have them, including the Polo until its last few runnings. I do like how Toyota took full advantage of the "requirement" and essentially created a continuous aero surface along the top of the extension which runs flat until the rear wing elements. That car is like a giant wedge in that sense, and seems to be making good downforce as well.

What I find also interesting is how the aero concept of the cars seems to have converged so well, first time around. Yes, the individual execution differs, but overall the flow management is much the same. I'm sure we were all thinking that we were being smart and outplaying others within the regulations without going full DTM-mode, but I suppose there is only so much that can be done on a road car base, aerodynamically. Do note that there seems to be two distinct approaches for the rear wing. Had VW been around, it would have been 3 for "fully separate upper and lower element" vs. 2 for "double decker with end plate + side element".

[NickRally]

All very good points Mrpengski.
Unfortunately there isn’t a single technical document that sets the conditions under which all WRC should be designed and build. My understanding is that form 400/01 is simply the homologation document for each car where the actual design features are recorded so that the cars can then be inspected before each rally. I think FIA has left itself a bit of flexibility in deciding the extent of the mods on each car in order to ensure closer competition as the cars are production based and not necessarily designed with competition in mind. I have to admit it is a bit peculiar to me and I would have enjoyed going through all the rules in a single document and seeing what’s ultimately possible and what not, but obviously the concept chosen by FIA works.
To answer your question about the yaw sensitivity of the cars, it is not easy without going to the wind tunnel and testing the various designs, but with this disclaimer in mind, I would say the cars with split upper and lower rear wing elements maybe hold an advantage in that respect, though this might be at the cost of reduced overall straight line downforce.
Having said that, connecting the two elements, does not automatically mean more yaw sensitive car, as shaping and sculpting the rear wing endplates can make the design less so as well as the design of the original car’s rear end.
On a different not, the external airbag concept sounds interesting and hints of one of the concepts chosen for a Martian landing module that was wrapped in a massive airbag at the point of hitting the Martian surface.

[Mirek]

My understanding is that form 400/01 is simply the homologation document for each car where the actual design features are recorded so that the cars can then be inspected before each rally.

Pre-event scrutineering is not being held to check if everything is correct according to the homologation. It's not possible simply due to the time required. What they do in scrutineering is mainly checking papers, safety equipment and sealing of particular parts such as gearboxes, differentials etc. (including spare ones). Of course they can find something against the homologation but more or less accidentally. For Your information scrutineering for Barum rally where I am sometimes present as organizer takes roughly 7 hours even when they do only the basic checking of every single entered car.

The deep check is being done in post-event scrutineering for which only several cars are being chosen (again due to the time required). Usually top-placed ones in their categories.

[NickRally]

Thanks for the correction Mirek. In that case I will rephrase what I said – “My understanding is that form 400/01 is simply the homologation document for each car where the actual design features are recorded so that the cars can then be inspected when required.”

[Mrpengski]

Nick, indeed the 400/01 form refers to the homologation dossier specific to each car. But in the working copy of the reg, this column is where you will find all the technical details. I know, because I work with it.

It's funny because if you see the 2017 LM GTE tech reg available on the FIA website, it has the exact same format as the WRC tech reg, but they left all the details intended "for manufacturers only" completely intact for public release. I don't know if it's an oversight by the FIA but the inconsistency is striking, to say the least.

Just saw the article on Race Tech magazine about the Fiesta. Interestingly, it also talks about the convergence of aero design, and how it could be considered as validation of each team's effort, where no one really has something coming out of the left field, so to speak. That's exactly how I felt when I saw the Polo with the final kit. In fact, the similarities were almost shocking, be it the treatment of the door extension or the rear wing. As reigning champions, I thought it was still fair to consider them as the yardstick for the new cars.

The fact of the matter is, though, I don't believe any rally will be won or lost purely on aero, at least not yet. And I hope we don't get to that point, ever.

Earlier I saw some confusion and misinformation about the central diff, but sadly I'm not at liberty to discuss anything interesting. For me it's just another black box, anyway ;)

[Mirek]

It was same at least with S2000 regs - all the details were not shown in the public documents.

[NickRally]

Very intriguing, thanks for sharing all this info Mrpengski. For me this is certainly very amusing, my initial impressions were that there wasn’t much hidden behind the fields with the text “400/01” and a lot was left to negotiation. How silly of me… I fully agree, it is a very puzzling attitude considering that even the F1 rules are publically available.
To be fair this is the first time I see someone directly stating in writing that there are two versions of the tech regs with some fields blanked off (or 400/01ed off), rather than implying the rest of the rules are in form 400/01 and it is genuinely appreciated.
Once again for someone like me coming from circuit racing this is highly unusual.

[OldF]

Here you can find the S2000 homologation regulations for 2010. An old one but I think it was the last one because any new homologations of S2000 cars was not allowed from 2011 and onward (if I recall correctly).

http://www.sarallying.co.za/nrc-info/regulations/ (FIA Homologation regulations, word document)

I think these specific regulations are for the ones who maintains the car and telling which part are free, which must be homologated etc.



Earlier I saw some confusion and misinformation about the central diff, but sadly I'm not at liberty to discuss anything interesting. For me it's just another black box, anyway ;)

Are you allowed to say what the confusion and misunderstanding was about without revealing any secrets?

[NickRally]

To add to OldF’s post, although maybe pushing you a bit Mrpengski (please don’t do anything that will put you in trouble), after you said there was a misunderstanding in the differential discussion earlier in the thread, it prompted me to summarise the potential options below, though of course I don’t know what restrictions are placed on the type of diffs and hidden in the differential filed of the tech regs under 400/01 expression, so here it is:
1. Spool – previous generation of cars, currently unlikely to be utilised by anybody other than when central diff is locked turning it into a spool
2. Symmetric epicyclic central differential, normally opened and requiring hydraulic pressure to lock - doubt its use on the current cars due to being symmetric and reducing the options available in varying the torque split front to back
3. Symmetric epicyclic central differential, normally locked and requiring hydraulic pressure to un-lock - doubt its use on the current cars due to being symmetric and reducing the options available in varying the torque split front to back
4. Asymmetric epicyclic central differential, normally opened and requiring hydraulic pressure to lock – one of the two options I would choose if I was designing the cars, possibly my first choice as it will allow precise control of the lock
5. Asymmetric epicyclic central differential, normally locked and requiring hydraulic pressure to un-lock – one of the two options I would choose if I was designing the cars, less precise control of the lock, but more robust in case of hydraulic failure
6. Independent two clutch packs type diff – very unlikely anybody was brave enough to embark on this and I wouldn’t be surprised if it is actually banned
7. Any other type of central diff – probably banned by the regs

[jparker]

So, we can ask Ogier "Is your diff locked or unlocked by hydrolics?". Hope he doesn't get the question wrong.

[NickRally]

Or rather "would you please state without any shadow of a doubt, when your hydraulics or control mechanism fail, is your diff locked or open?" :)

[Mrpengski]

What, you weren't satisfied with "we lost hydraulic so we were RWD"? :D

I can't say anything chiefly because I myself don't fully understand everything, so I can't distinguish what's common knowledge and what's trade secret. How much detail is available in the public domain, from the last generation of active central diff cars? What would surprise me is if 1) this technology from a decade ago is still considered secret, and 2) if there were in fact any groundbreaking development this time around. I have only recently joined rally from circuit side, and one thing I definitely learned is that everything is much more conservative and tend to gravitate towards proven solutions, rightfully so.

[NickRally]

By the way, one other question on diffs - Mrpengski are you happy to tell us what the full version of the tech regs says about the front and rear diffs – presumably it requires purely mechanical units with no active functions? Or does it allow for more freedom there?

[Mrpengski]

We will have to wait until they publish the new regs in the fully condensed format, like article 255a for 2016 which you can find on the FIA website. From 2016:

1333

[br21]

255a for 2017, so new spec WRC cars is available on FIA www already for many months, currently freshly updated.

[NickRally]

br21 - the updated rules still have the relevant fields blanked off under the 400/01 banner

[br21]

yes, homologation regulations will never be officialy published.

[NickRally]

Why? Why are the restrictuon on the size of the diffuser or the type of differential for example such big secret in rallying, but not in just about any other form of motorsport?

[Mrpengski]

That's another funny point. The 2016 255a is cleaned up and presented in portrait A4 format, which is what is typically available to the public. They haven't done that yet with the 2017 255a, rather just the "manufacturer only" info is replaced by a reference to 400/01, but the landscape A3 page format of the full working copy remains. What really gets me is, that when they decide to convert the redacted version to cleaned up version, in some cases more information becomes available. If you open 2016 vs. 2017 side by side and find the same section I posted above, you will see what I mean. :rolleyes:

[Lundefaret]

Re: doors. Don't forget that these doors are first gutted out (OEM side impact beam and all) then filled back with energy-absorbing foam. Of course, the OEM beam is replaced by the roll cage, but this is not realistic for a road car, and neither is filling the entire door + outer extension with foam. Among other things, the window won't go down! Incidentally, in my previous job I was involved in a lightweight electric car project with composite monocoque and bodywork. Inside the door was a CFRP side impact beam which housed an outside-firing airbag. I believe it was for pedestrian protection more than occupant protection, but interesting nonetheless. So maybe something like this could be applied to road cars, before we see extra thick rally-style doors.
.

As you say, maybe not that relevant for a present VW Golf, but more for a future 2-seater individual electric transportation pod, where seating is for-aft, and the "car" is made narrow to go two side by side in a normal lane.

[Mirek]

As you say, maybe not that relevant for a present VW Golf, but more for a future 2-seater individual electric transportation pod, where seating is for-aft, and the "car" is made narrow to go two side by side in a normal lane.

For me it makes no sense to introduce something like that.

[OldF]

Tommi Mäkinen said in today’s newspaper Helsingin Sanomat that the problem with transmission in Argentina was caused by jammed planetary gear assembly. This mean that at least Toyota use a planetary centre differential and can use a fixed uneven torque split regardless of grip.

http://www.hs.fi/urheilu/art-2000005215136.html

For some reason Google won’t translate this page.:confused:

[NickRally]

Thanks for the info OldF, asymmetric epicyclic centre diff makes a lot of sense.

Incidentally, watching the cars in slow-ish turns, they still understeer quite a lot, so there is still room for improvement, i.e. reducing or even cancelling this understeer without making them too nervous in high speed corners. No doubt large player in this process will be the set-up of the centre diff.

[Sulland]

Looking at the C3 after almost half the 2017 season.
Where lies its strong and weak areas?

[gorganl2000]

Looking at the C3 after almost half the 2017 season.
Where lies its strong and weak areas?

i'm not certain of the technical stuff...i think overall its a decent car with competitive speed but it does seem to want some further refinements maybe with the diff settings and suspension based on media and the forum

actually, i think the weakest area has nothing to do with the car so far this year----its drivers controlling the car

Breen is somewhat of a "junior" wrc driver and he is doing fairly well, but the other two drivers...smh, i don't even want to comment on their performances so far in 2017.

[Mirek]

Shortly after VW entered WRC their technical director Willy Rampf said one thing which in my opinion nicely sums the situation about C3. He said that the first and foremost important feature of the car is to give the driver confidence. If driver isn't confident with it, no matter how advanced it is, he isn't going to achieve anything.

[NickRally]

Shortly after VW entered WRC their technical director Willy Rampf said one thing which in my opinion nicely sums the situation about C3. He said that the first and foremost important feature of the car is to give the driver confidence. If driver isn't confident with it, no matter how advanced it is, he isn't going to achieve anything.

This is a really good point and one that has proven to be the correct over and over again in my career.

[AnttiL]

http://yle.fi/urheilu/3-9647211?origin=rss

This Finnish article suggests that the problem of Citroen this season are Öhlins dampers, which were selected because they couldn't afford better ones

[Sulland]

I thought Øhlins were very good dampers, but have they fallen behind in Rally?

[AMSS]

I thought Øhlins were very good dampers, but have they fallen behind in Rally?

I think it`s a bit unfair to blame Öhlins, they have only become involved since after rally Sweden as consults, the dampers were/are Citroen in house design but now apparently they need help.
Also the reporter has it all wrong, at least in customer racing Öhlins are more on the expensive side compared to many other brands.

[tommeke_B]

The dampers being used in works WRC cars aren't exactly "customer racing". Who knows they can have some technology we' may see in "customer racing" only next decade. If Citroën decides to not work with Reiger, I think it's more likely they do it because no opponent (like M-Sport) would benefit from the knowledge Reiger may gather from Citroën... Hyundai has also changed supplier, they used Reiger with the first i20 WRC, now they use EXT. ;) As a works-team, not being able to afford it sounds rubbish to me.

[AMSS]

The dampers being used in works WRC cars aren't exactly "customer racing". Who knows they can have some technology we' may see in "customer racing" only next decade. If Citroën decides to not work with Reiger, I think it's more likely they do it because no opponent (like M-Sport) would benefit from the knowledge Reiger may gather from Citroën... Hyundai has also changed supplier, they used Reiger with the first i20 WRC, now they use EXT. ;) As a works-team, not being able to afford it sounds rubbish to me.

This is what I meant, if they are more expensive in customer racing than they are probably not cheaper with works teams..
Also it`s not that big a jump between customer racing shocks and works shocks, mostly bigger weight reductions in works dampers but since they are limited by rules in what materials they can use it`s really not that big a difference. Different yes, massive difference no. And yes I`ve seen the inside of 3 manufactorers WRC dampers from previous generation cars. This years cars I haven`t seen but I doubt they invented something revolutionary that`s only available in the next decade to "normal" people..

[Lundefaret]

I thought Øhlins were very good dampers, but have they fallen behind in Rally?

I dont know about Öhlins factor in the Citroën problems, but will comment in general:

Öhlins and Öhlins are not the same thing.
A damper is as good as the effort that is put in it, and that is very budget driven.

I think Öhlins was last used in WRC in the Prodrive MINI, and that was after a sucsessfull change from BOS to Öhlins on the S14 that Grönholm competed with.
Both those dampers was competitive, though Prodrive under estimated the need for damper travel on the MINI - but that was not Öhlins.

Citröen has had a history making their own dampers (after the ex-tc I think?), but it has been a wish from several that they get outside assistanse.
But though the dampers seem to have some protection problems (bump stop and last high speed movement before bumpstop) its still difficult for me to understand how they could have ended up in this situation. I think there must be more to this story.

[Lundefaret]

This is what I meant, if they are more expensive in customer racing than they are probably not cheaper with works teams..
Also it`s not that big a jump between customer racing shocks and works shocks, mostly bigger weight reductions in works dampers but since they are limited by rules in what materials they can use it`s really not that big a difference. Different yes, massive difference no. And yes I`ve seen the inside of 3 manufactorers WRC dampers from previous generation cars. This years cars I haven`t seen but I doubt they invented something revolutionary that`s only available in the next decade to "normal" people..

In a factory damper you can build a more specific damper, more tailor made, thats the biggest difference. You can chose some different tech, and you have specific damper engineers working on it.

For me its strange if not one of the teams "take over" ZF Sachs, but dont know if its possible?

[AMSS]

In a factory damper you can build a more specific damper, more tailor made, thats the biggest difference. You can chose some different tech, and you have specific damper engineers working on it.

For me its strange if not one of the teams "take over" ZF Sachs, but dont know if its possible?

This was exactly what I meant /more tailor made/
Actually Skoda now uses ZF Sachs so they are still in the VAG group, and VW WRX cars use Sachs.

[Rally Power]

This talk about the C3 dampers is like Iraqis mass destruction weapons: a myth.

Last year Citroen did a remarkable job managing to get the DS competitive again. Their in-house developed dampers were able to perform outstandingly at the most demanding WRC terrains, but now everybody seems to believe that, somehow, they’re not able to produce good dampers any more…seriously?

IF something is wrong with the car shouldn’t we be looking at the new active differential and the set up issues brought by it, which also arouse problems to other manus?

[dimviii]

http://yle.fi/urheilu/3-9647211?origin=rss

This Finnish article suggests that the problem of Citroen this season are Öhlins dampers, which were selected because they couldn't afford better ones

I don't think that he has a clue about.

[Mirek]

Actually Skoda now uses ZF Sachs so they are still in the VAG group.

AFAIK they didn't want to give up working with Reiger but they had to.

[AMSS]

AFAIK they didn't want to give up working with Reiger but they had to.

Yes so I heard as well

[Sulland]

Mikkelsen comes with Sachs/VW experience.
So if it something with the suspesion/dampers, he will/has give(n) info.

Øhlins will find issues if there are any, of they put their mind 100% into the task.
Citroen will have a ton of data from DS3 and from C3 to model and find challenging areas.

[br21]

If there is a problem in the dampers it's because of decision of Citroen engineers decisions.
BTW:
- new C3 R5 will be on Reiger
- bump stop and wrong management of it (last moment of damper travel) was/is big problem in Ohlins DS3 R5 dampers since the beginning, but it's also mainly because of PSA engineers decisions.

[Ctesibios]

Did the team or the drivers confirm there was a suspension/damper issue?

What I saw in Portugal was Meeke hitting a stone or small wall which of course broke the suspension! I am not sure what happened exactly to Breen?

Sent from my LG-H831 using Tapatalk

[AnttiL]

I am not sure what happened exactly to Breen?


He just had a spin.

[Rally Power]

He just had a spin.

When Citroen’s less experienced driver manages to be 5th overall (winning a stage and making several top 5 times before being forced to ease up the pace, in order to ensure some manu points) and his only issue during the whole rally is a spin, one has to ask: where are those major C3 tech problems?

[Ctesibios]

When Citroen’s less experienced driver manages to be 5th overall (winning a stage and making several top 5 times before being forced to ease up the pace, in order to ensure some manu points) and his only issue during the whole rally is a spin, one has to ask: where are those major C3 tech problems?
+1

[Sladden]

Breen had a massive compression in the same corner that resulted in broken gearbox. It was pure luck he did not end up like Meeke.

[EstWRC]

+1

+2

[mknight]

Breen had a massive compression in the same corner that resulted in broken gearbox. It was pure luck he did not end up like Meeke.

Your are talking about Argentina.

Rally Power is talking about Portugal.

That said Neuville almost rolled on the same compression as Meeke in Argentina in case you missed it.

[Sladden]

Your are talking about Argentina.

Rally Power is talking about Portugal.

That said Neuville almost rolled on the same compression as Meeke in Argentina in case you missed it.

Breen had a moment there too.

[NickRally]

Finally I have some time to sit down and write again. I was planning to pick up the subject of suspension kinematics characteristics (i.e. camber change with bump and so on), but now that there was news on Citroen using homologation jokers to update their car and while the sporting side is being discussed in the Citroen thread, I thought I should start a similar one on the technical side here.
First the “easy” one on aero – I noticed that while testing for Poland, C3 was run with and without lower closing panels behind the rear wheels. Short of these being knocked off (something I tend to doubt in this instance), I can only assume Citroen was interested in finding out the effect of these panels on rear downforce in a fast gravel rally. Also note the missing mud flaps in either case, which is another thing that would affect rear aero.

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_7.jpg

Now on a more challenging subject – differentials and I should start by saying that I wrote the text below in the morning, but I can now see that another forum member has posted some numbers regarding the Citroen differentials in the WRT thread. Anyway, here is what I wrote:

In the press release it was said that Citroen have changed the rear differential rail (I assume ramp angles) and front/rear torque split. I will start with a very wild guess (and this is from someone that has zero experience of vehicles with centre diffs) and say that they have gone towards a more equal split of torque between front and rear axles with the newly homologated parts.

In my simplistic view of the world, I originally thought that a bigger mechanical split between the front and rear axles on the asymmetric diff coupled with the traditional hydraulic locking, would provide for wide ranging opportunity for varying the torque split - for example let’s say we design in an extreme mechanical split of 20/80 front/rear: when the diff is open that is what we would get, 20/80 front/rear, but as we start applying hydraulic pressure and locking the differential, in theory we can get to 50/50 split. This is where things get complicated though – as we apply locking, the actual torque split (rather than the theoretical one) would more and more depend on the grip each axle has rather than our wishes. In the extreme, with completely locked diff and the front axle in the air, all the torque would go towards the rear despite the locked diff. This make me thing that having a large mechanical front/rear split would be more beneficial on tarmac where you would naturally exploit the handling benefits of rear wheel drive car in tight turns, while being also able to lock the diff momentarily when you need to induce some stability in the car. At the same time this arrangement would be a bit more challenging to make it work on gravel where the grip on each wheel would vary to much greater extent than tarmac (it would seem to me) and so when we lock the diff to induce stability, this could actually make the car wildly switching from under to over steer and make it feel very inconsistent.

Funnily enough, with my lack of experience in four wheel drive competition cars, that is exactly the kind of arrangement I would have designed – a large mechanical split, which can then be varied by hydraulic pressure locking, but now that I went through that theory, it appears very flawed to me. It now seems to me that a bit more balanced mechanical split coupled with hydraulic locking would provide a more consistent platform. This is not to say that 50/50 mechanical split is the way to go, but that if you stray wildly from 50/50 mechanical split, you might be in a danger zone. Once again, the disclaimer here is that all this comes from someone with zero experience with centre diffs in race conditions.

Going back to the rear diff update and assuming it is the mechanical diff ramp angles that they have changed, this can of course bring its own benefits when it comes to making the car more consistent, with more locking on overrun (braking) providing a lot of benefit in stabilising the corner entries (at least in circuit racing) and then having not too much and not too little lock on throttle dependent on power to grip ratio.

Anyway, that is my take on the situation, other opinions welcome, especially if someone has experience from going testing different mechanical splits centre diffs :)

[stefanvv]

Finally I have some time to sit down and write again. I was planning to pick up the subject of suspension kinematics characteristics (i.e. camber change with bump and so on), but now that there was news on Citroen using homologation jokers to update their car and while the sporting side is being discussed in the Citroen thread, I thought I should start a similar one on the technical side here.First the “easy” one on aero – I noticed that while testing for Poland, C3 was run with and without lower closing panels behind the rear wheels. Short of these being knocked off (something I tend to doubt in this instance), I can only assume Citroen was interested in finding out the effect of these panels on rear downforce in a fast gravel rally. Also note the missing mud flaps in either case, which is another thing that would affect rear aero.http://www.geocities.ws/rallytech/aero/citroen/C3_aero_7.jpgNow on a more challenging subject – differentials and I should start by saying that I wrote the text below in the morning, but I can now see that another forum member has posted some numbers regarding the Citroen differentials in the WRT thread. Anyway, here is what I wrote:In the press release it was said that Citroen have changed the rear differential rail (I assume ramp angles) and front/rear torque split. I will start with a very wild guess (and this is from someone that has zero experience of vehicles with centre diffs) and say that they have gone towards a more equal split of torque between front and rear axles with the newly homologated parts.In my simplistic view of the world, I originally thought that a bigger mechanical split between the front and rear axles on the asymmetric diff coupled with the traditional hydraulic locking, would provide for wide ranging opportunity for varying the torque split - for example let’s say we design in an extreme mechanical split of 20/80 front/rear: when the diff is open that is what we would get, 20/80 front/rear, but as we start applying hydraulic pressure and locking the differential, in theory we can get to 50/50 split. This is where things get complicated though – as we apply locking, the actual torque split (rather than the theoretical one) would more and more depend on the grip each axle has rather than our wishes. In the extreme, with completely locked diff and the front axle in the air, all the torque would go towards the rear despite the locked diff. This make me thing that having a large mechanical front/rear split would be more beneficial on tarmac where you would naturally exploit the handling benefits of rear wheel drive car in tight turns, while being also able to lock the diff momentarily when you need to induce some stability in the car. At the same time this arrangement would be a bit more challenging to make it work on gravel where the grip on each wheel would vary to much greater extent than tarmac (it would seem to me) and so when we lock the diff to induce stability, this could actually make the car wildly switching from under to over steer and make it feel very inconsistent.Funnily enough, with my lack of experience in four wheel drive competition cars, that is exactly the kind of arrangement I would have designed – a large mechanical split, which can then be varied by hydraulic pressure locking, but now that I went through that theory, it appears very flawed to me. It now seems to me that a bit more balanced mechanical split coupled with hydraulic locking would provide a more consistent platform. This is not to say that 50/50 mechanical split is the way to go, but that if you stray wildly from 50/50 mechanical split, you might be in a danger zone. Once again, the disclaimer here is that all this comes from someone with zero experience with centre diffs in race conditions.Going back to the rear diff update and assuming it is the mechanical diff ramp angles that they have changed, this can of course bring its own benefits when it comes to making the car more consistent, with more locking on overrun (braking) providing a lot of benefit in stabilising the corner entries (at least in circuit racing) and then having not too much and not too little lock on throttle dependent on power to grip ratio.Anyway, that is my take on the situation, other opinions welcome, especially if someone has experience from going testing different mechanical splits centre diffs :)I'm not a technician in this respect, but isn't an active center diff supposed to give You optimum performance in various corners (in some degree). There used to be fixed ratio diffs already in 90's I believe.

[NickRally]

The only thing that would give you the optimum grip for each wheel in all conditions (short of using one electrical motor per wheel) is a transmission consisting of one clutch pack per wheel with continuously variable engagement, but as we established earlier in the thread, we do not believe such systems are reliable enough, and at the same time they are illegal in WRC.

[stefanvv]

That's probably the best way to go, and where the hybrids will come along.

[wrc2017]

Very interesting. So your theory explains what some of us expected. Citroen has designed torque split thats bias towards tarmac, and hoped it they could 'make' it work on gravel via hydraulics, leaving it unpredicable?
Also on the pictures is the negitive chamber on full droop what you would expect?

[GravelBen]

In my simplistic view of the world, I originally thought that a bigger mechanical split between the front and rear axles on the asymmetric diff coupled with the traditional hydraulic locking, would provide for wide ranging opportunity for varying the torque split - for example let’s say we design in an extreme mechanical split of 20/80 front/rear: when the diff is open that is what we would get, 20/80 front/rear, but as we start applying hydraulic pressure and locking the differential, in theory we can get to 50/50 split. This is where things get complicated though – as we apply locking, the actual torque split (rather than the theoretical one) would more and more depend on the grip each axle has rather than our wishes. In the extreme, with completely locked diff and the front axle in the air, all the torque would go towards the rear despite the locked diff. This make me thing that having a large mechanical front/rear split would be more beneficial on tarmac where you would naturally exploit the handling benefits of rear wheel drive car in tight turns, while being also able to lock the diff momentarily when you need to induce some stability in the car. At the same time this arrangement would be a bit more challenging to make it work on gravel where the grip on each wheel would vary to much greater extent than tarmac (it would seem to me) and so when we lock the diff to induce stability, this could actually make the car wildly switching from under to over steer and make it feel very inconsistent.

Funnily enough, with my lack of experience in four wheel drive competition cars, that is exactly the kind of arrangement I would have designed – a large mechanical split, which can then be varied by hydraulic pressure locking, but now that I went through that theory, it appears very flawed to me. It now seems to me that a bit more balanced mechanical split coupled with hydraulic locking would provide a more consistent platform. This is not to say that 50/50 mechanical split is the way to go, but that if you stray wildly from 50/50 mechanical split, you might be in a danger zone. Once again, the disclaimer here is that all this comes from someone with zero experience with centre diffs in race conditions.

I only have experience of such systems in road cars rather than competition, but that sounds quite similar to the Subaru DCCD system first used in the Type-RA homologation Imprezas in the 90s.

They had 36F:64R mechanical torque split, with variable locking centre diff (capable of full lockup but only recommended for gravel/snow etc as it would put a lot of strain on the drivetrain on tarmac). In the road cars its driver controlled with a small dial so you tend to set it and leave it rather than adjusting mid corner, but electronic controllers were used for competition (and later introduced to the road cars too).

The ones I've driven were far more neutral, balanced and understeer-resistant than normal 50:50 viscous LSD Subarus, but also snappier when they let go and I know they caught out a few people who expected idiot-proof predictability. IIRC they also had a fairly agressive rear LSD which may have contributed to that as well. Heaps of fun anyway.

I disagree about locked centre diffs being unpredictable on gravel though, at least in my (enthusiastic but non-competition) experience - yes the torque split is effectively determined by traction available, but being locked the front and rear axles rotate at the same speed so you won't get either axle overspeeding relative to the other. One of my vehicles has both open centre diff and locked centre diff 4wd modes, and on rough inconsistent gravel it behaves much more predictably when locked. Does require a more agressive corner entry to avoid understeer though I guess.

[traxx]

First the “easy” one on aero – I noticed that while testing for Poland, C3 was run with and without lower closing panels behind the rear wheels. Short of these being knocked off (something I tend to doubt in this instance), I can only assume Citroen was interested in finding out the effect of these panels on rear downforce in a fast gravel rally. Also note the missing mud flaps in either case, which is another thing that would affect rear aero.

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_7.jpg



Mud flap ?

[NickRally]

Wrc2017 – wheel cambers: yes, the positive cambers in full droop are inevitable consequence of the type of suspension used, but there are some differences between the teams, which I would like to analyse in pictures when I get the time.

GravelBen – thanks for the additional notes. I should also clarify that what I meant is the car might feel inconsistent when switching from open diff with massive rear torque bias to locked diff, rather than a constantly locked centre diff being inconsistent, which is what we had last year. With centre spool (locked diff), the rest of the car would be setup to deal with it and also the driver would adapt to such arrangement.

traxx – mud flaps or mud guards (depending on your preference), which Citroen have been using in gravel rallies. Not only this, but while Toyota and Hyundai have a diffuser ahead of the rear wheels, Citroen used to have another mud guard there acting like a negative gurney, sort of lift creator rather than downforce.

[GravelBen]

GravelBen – thanks for the additional notes. I should also clarify that what I meant is the car might feel inconsistent when switching from open diff with massive rear torque bias to locked diff, rather than a constantly locked centre diff being inconsistent, which is what we had last year. With centre spool (locked diff), the rest of the car would be setup to deal with it and also the driver would adapt to such arrangement.


Ah I get your meaning now, agree with that.

[Steve Boyd]

traxx – mud flaps or mud guards (depending on your preference), which Citroen have been using in gravel rallies. Not only this, but while Toyota and Hyundai have a diffuser ahead of the rear wheels, Citroen used to have another mud guard there acting like a negative gurney, sort of lift creator rather than downforce.
Mud flaps in accordance with FIA Appendix J - Article 252 - 7.7 (http://www.fia.com/file/51626/download/12791?token=bM0OZdyu) are required on gravel rallies. They aren't aerodynamic appendages added at the discretion of the vehicle builders.

[NickRally]

Mud flaps in accordance with FIA Appendix J - Article 252 - 7.7 (http://www.fia.com/file/51626/download/12791?token=bM0OZdyu) are required on gravel rallies. They aren't aerodynamic appendages added at the discretion of the vehicle builders.

Correct. I was just pointing out to the fact that they are testing without them, no doubt in pursuit of finding some answers.

[NickRally]

Actually to add to my post above, the mud guards in front of the wheels are not part of the FIA requirements as far as I can see.

[Steve Boyd]

Actually to add to my post above, the mud guards in front of the wheels are not part of the FIA requirements as far as I can see.
I read the regulation to mean that mud flaps in front of the front wheels are optional but those shown on the drawing in front of the rear wheels are required. Either way you don't have them on tarmac so both configurations really need to be tested and the rest of the bodywork needs to be optimised to deliver the desired performance compromise between both.

[NickRally]

Looking at the image below, I can't see mud flaps in front of the rear wheels:

www.rallyitaliasardegna.com/wp-content/uploads/ngg_featured/HANNINEN-1.JPG

http://www.rallyitaliasardegna.com/wp-content/uploads/ngg_featured/HANNINEN-1.JPG

[itix]

Too much dampers and aero lately!
Saw this picture in one of Dimitris posts:
https://pbs.twimg.com/media/DDerxkwW0AAZw7u.jpg

And it got me thinking. The Yaris has the radiators in-line with the intercooler first (also a massive intercooler) and the engine radiator second. It makes sense from a power perspective given that the colder and denser the air is, the more you can manage to squeeze into the engine. It does however channel warmer air through the radiator and could explain the cooling problems they had at warmer rallies. Do we know the other team's set up?

[dimviii]

Too much dampers and aero lately!
Saw this picture in one of Dimitris posts:


that's why I posted this photo,hadnt seen like this before.

[racerx1979]

Too much dampers and aero lately!
Saw this picture in one of Dimitris posts:
https://pbs.twimg.com/media/DDerxkwW0AAZw7u.jpg

And it got me thinking. The Yaris has the radiators in-line with the intercooler first (also a massive intercooler) and the engine radiator second. It makes sense from a power perspective given that the colder and denser the air is, the more you can manage to squeeze into the engine. It does however channel warmer air through the radiator and could explain the cooling problems they had at warmer rallies. Do we know the other team's set up?

The Yaris has two radiators with the intercooler in the middle. The intercooler is not in front of the radiators. All three are on the same plane.

[itix]

The Yaris has two radiators with the intercooler in the middle. The intercooler is not in front of the radiators. All three are on the same plane.
That may be, but what would the end ones be then? There are no visible pipes going in or out. Behind is most definitely the main radiator as you can see the coolant pipes going in and out of it.

For me the black strips are just something to fix the radiators in place because it looks like double end tanks where the coolant pipes enter the radiator. That's why I thought the entire front was an intercooler. The side ones are too big to be oil and gearbox coolers in my opinion.

[dimviii]

The Yaris has two radiators with the intercooler in the middle. The intercooler is not in front of the radiators. All three are on the same plane.

we have to watch some better photos,the right one as we look the photo is definitely intercooler,just watch the pipe which comes from behind the engine where I suppose is the turbo.
for sure something different we ve seen till now,thats why I posted the photo.
Can we have some more photos closer to engine bay?

[racerx1979]

The right and left coolers have small inlets /outlets. Not large enough for an intercooler. The center end tank is sufficient for an intercooler. I'll try to find a better image.

[NickRally]

racerx1979 is right, the centre one has the right size pipe for an intercooler (interestingly it is an air-to-air one), while the hoses on the two radiators either side are the right size for the cooling system, which could have the two radiators working in parallel (most likely) or in series:

http://www.geocities.ws/rallytech/aero/toyota/yaris_engine_12.jpg


I went through my files and only found a similar image for one other car - the Citroen, which I took in Portugal:

http://www.geocities.ws/r/a/rallytech/aero/citroen/C3_engine_8.jpg

[dimviii]

The right and left coolers have small inlets /outlets. Not large enough for an intercooler. The center end tank is sufficient for an intercooler. I'll try to find a better image.

yes you are right,with the photo Nick posted its clear.The pipe from behind the engine is going to center and not to the right.

[SubaruNorway]

You always talk about the drivers side as left btw guys ;)

[itix]

yes you are right,with the photo Nick posted its clear.The pipe from behind the engine is going to center and not to the right.
I agree that the big "vacuum cleaner" pipe in the center is the intercooler pipe, but what has been suggested is that the separating black "strips" divides the radiator into three.

While that could be, there are also two separate end tanks lengthwise on the car and the coolant pipes are definitely connected to the rearmost radiator (as it goes into the rearmost end tank)...

So if the front radiator is indeed three pieces, we are looking at 3 total very large radiators in addition to the intercooler (which is puzzling), or two separate end tanks on the same, very big, and very complicated cooling radiator with a "slot" in the middle for the intercooler (which also makes very little sense).

I may be wrong but I thought the entire front radiator was an intercooler (including the sections on either side of the "dividers")

Edit: now that I look at it more carefully, it actually looks like the pipes enter on the back of the end tanks so I'm likely wrong. What is funny is that the pipes entering to the right and left look the same size, so if they are indeed both cooling pipes, how does the water flow to the other side? (unless it really is a mega complicated radiator with a slot in it). Interesting set up for sure.

[SubaruNorway]

Maybe it's made like this so that they can block one of the radiators off if one breaks?

[itix]

Meanwhile the Citroen setup is classic PSA motorsports setup. Cooling radiator on one side, intercooler on the other side.

[Sulland]

How many attachment points does the back wing of the Ford have?
2 x falloff gives MSport a challenge to improve !

[itix]

How many attachment points does the back wing of the Ford have?
2 x falloff gives MSport a challenge to improve !

From the videos and photos it looks like the legs sheared off..

[ToughMac]

Could it be a material problem in that it just suffers fatigue with all the jumps and bumps?

[NickRally]

The reasons for the failure would be any one of these:
1. Design does not account for ultimate loads encountered in service.
2. As above but in respect to fatigue loads.
3. Material batch problem.
4. Manufacturing issue not caught up by the inspection department.
5. Assembly issue.

[mknight]

Cracks in Carbon fiber are very hard to discover no? Also much more prone to sharp impact damage.

[TWRC]

Meanwhile the Citroen setup is classic PSA motorsports setup. Cooling radiator on one side, intercooler on the other side.
Classic for Citroën WRCs from the C4 onwards (Xsara had different layout), and classic for Peugeot, who always put the water radiator on the left side and intercooler on the right to try and counterbalance the engine weight. PSA R5s have this classic Peugeot layout as well, but there it was mostly dictated by regulations (intercooler has to be placed where it is on the road car, which is right side on both the 208 and DS3).

[TWRC]

Cracks in Carbon fiber are very hard to discover no? Also much more prone to sharp impact damage.
In my university they have developed special fibers for airplanes that have fluorescent liquid in the middle, so when they fail, they release this fluid, and you can assess the damage by looking at the part with a UV light. Although I know very little about this, it was only mentioned to us during a lecture.
Also, there are some self-healig solutions, like where they make little "globes" filled with glue, so when a crack reaches them and they break, they release this glue and stop or at least delay the further movement of the crack.

[NickRally]

Yes, cracks in carbon fibre parts are more challenging to detect and properly assess, it usually involves ultrasound inspection (more commonly) or CT scans (computerised tomography - more rarely in motorsport due to cost). In motorsport once delamination inside the part is detected, you wouldn't automatically scrap it - if you have the option you might decide to put in a test equipment and apply predetermined load to it and see if the delamination grows, if it doesn't part can be reused depending how critical the application is. If you can't stress it in a lab, then you have to use your experience and judgement. It has to be noted that doing ultrasound inspection "in the field" is possible and should be done regularly on critical carbon fibre components - the teams should carry portable equipment for this.
Also the carbon fibre resin systems include various toughening options (the spheres refered to in the previous post is one of them) to stop cracks in the resin.
I haven't had a chance to look closely at the failed attachment points on the Fiesta's wing, but I wouldn't be surprised if this also involved failed bond between the carbon fibre laminate and a metal insert in it (a hard point in the laminate). It basically can be any one of numerous failure modes that could have occurred.

[krzaki]

Sorry for OT
Does anybody know what technical problems had Latvala?

[Munkvy]

Sorry for OT
Does anybody know what technical problems had Latvala?

From the onboard it looked like gearbox, he was braking for the chicance and the dash said he was still in 6th gear, and should have been in 1 or 2. And then as he pulled round crawling it was still in 4th, so I suspect either the box itself or the controlling functions?

[itix]

From the onboard it looked like gearbox, he was braking for the chicance and the dash said he was still in 6th gear, and should have been in 1 or 2. And then as he pulled round crawling it was still in 4th, so I suspect either the box itself or the controlling functions?
From the onboard you can also see what looks like a jolt in the entire car during breaking at one downshift. Dunno if that's just a coincidence with a hole in the ground or indeed the gearbox but pretty much everything points towards it...

[pantealex]

Sorry for OT
Does anybody know what technical problems had Latvala?

Clutch and flywheel broked, not gearbox, they used same gearbox in sunday.

Reason for no Rally2 to Esapekka Lappi was lost oil pressure in engine.

[noel157]

Clutch and flywheel broked, not gearbox, they used same gearbox in sunday.

Reason for no Rally2 to Esapekka Lappi was lost oil pressure in engine.

Thought it was front right suspension damage rather than oil pressure for Lappi?

[itix]

Clutch and flywheel broked, not gearbox, they used same gearbox in sunday.

Reason for no Rally2 to Esapekka Lappi was lost oil pressure in engine.
Interesting, thanks!

[pantealex]

Thought it was front right suspension damage rather than oil pressure for Lappi?

Suspension was reason for retire but oil pressure problems for no Rally2. (engine was damaged in that suspension failure)

[itix]

Those fluent in the technical rally car knowhow, does the modern rally cars have some kind of guard or protection for a flywheel blowing out or coming loose?

Having been unfortunate enough to have seen the aftermath of a flywheel going on a trip on a former colleges (he is alive and well, the engine was mounted longitudinally) dragrace car I know the consequences it can have.

[Fast Eddie WRC]

Anyone know why the MSport rear spoiler might have broken off ? Poland was the second time one has done this on the '17 car and it cost Tanak the win IMO...

[noel157]

Anyone know why the MSport rear spoiler might have broken off ? Poland was the second time one has done this on the '17 car and it cost Tanak the win IMO...


Who else has had it happen?

[AnttiL]

Who else has had it happen?

Østberg in Sweden.

[mmm]

Who else has had it happen?

Ostberg in Sweden.

Anyways they have some serious miss-calculations when designing the parts. The diffusors broke off in a similar way - the area right around the bolts is too weak.

[NickRally]

Citroen keep persevering with their "nice" lift creating mud flaps in front of the rear wheels, only team to do so, I find this very peculiar:

http://www.geocities.ws/rallytech/aero/citroen/C3_aero_9.jpg

Compare this to Ford:

http://www.geocities.ws/rallytech/aero/ford/Fiesta_aero_2.jpg

Not to mention Toyota and Hyundai who have gone a step further and designed some nice little venturis in this region.

[mknight]

What I found strange is how "soft" the guiding vanes in the diffuser on some of the cars are. In quite a lot of jumps you seem them flapping around wildy. (Citroens and Toyotas at least)

Yes if they are too rigid they will break off easily when car touches the ground, but if they are too soft they won't really help in keeping laminar flow. Maybe they flap only during the jump and not when actually doing the work close to the road?

[Mrpengski]

Nick, supposedly the flaps forward of wheels have some masking effect and can reduce the pressure if done right. Sorta like the rear wheel scraper certain F1 runs I guess ;)

We tested both rigid and flappy diffuser fins during development. Everyone was expecting the fins to disappear very quickly, but turned out that they were not really getting damaged, if at all, under normal use. In the end, it was better to risk losing the bottom 10mm of rigid fins, than to have flappy fins destroying all the flow through the diffuser.

[NickRally]

Thanks for the insight Mrpengski, this is really appreciated - you are quite right, there was so much discussion about the damage all these fins will suffer and yet it is not really happening.

On the forward facing flaps, aren't the ones we use still on the top surface ;). Actually this reminds of a story I read long time ago about the time when Dan Gurney started using little trim tabs on the rear wing (which are now known as gurneys) and the fact that he tried to hide their real purpose by saying they are to stiffen the wing, so another team copied him, but placed the tabs on the underside supposedly to not increase the air resistance of the wing...:)

[Revman]

Quick newbie questions.....

1) Is the intake on the roof for driver ventilation?
2) Does the driver consult with an engineer prior to shock tuning between stages?
3) Is there a development freeze on chassis, body, and/or engine to contain costs? I think I heard three years. What can the teams do during that time in terms of development?
4) These cars costs $900,000 US compared to a NASCAR at $250,000 US. NASCAR struggles for sponsorships and TV packages to keep teams alive. How does the WRC do it?...Maybe not a purely technological questions, but indirectly related.

Thank you

[Mrpengski]

Quick newbie questions.....

1) Is the intake on the roof for driver ventilation?
2) Does the driver consult with an engineer prior to shock tuning between stages?
3) Is there a development freeze on chassis, body, and/or engine to contain costs? I think I heard three years. What can the teams do during that time in terms of development?
4) These cars costs $900,000 US compared to a NASCAR at $250,000 US. NASCAR struggles for sponsorships and TV packages to keep teams alive. How does the WRC do it?...Maybe not a purely technological questions, but indirectly related.

Thank you

Hi Revman,

1) Yes, roof vent (bit of a misnomer) for cockpit ventilation.
2) Teams run a pre-event test in representative terrain/surface before each rally, which is where the baseline setup of the cars are determined. Throughout the weekend, the crew (driver/codriver) can and do constantly make adjustments to the dampers, ride height, etc. as the conditions change. The race team/engineers are all involved in this together of course.
3) "Freeze" might be too strong a word here. Yes, the regulation which came into effect this year stays until (at least) 2019. Teams must homologate certain parts of engine, suspension, chassis, hydraulics and bodywork, and they are indeed "frozen". We are allowed a number of "jokers" to spend, i.e. make modifications to homologated parts. Some parts are homologated as options, so different types can be introduced throughout the year. Other parts are completely free in terms of development. So it's not a development war, but not completely restricted either.
4) $900k is a very conservative number ;) I myself still can't fully make sense of the economic side of things, I just hope every team has deep pockets and everyone can race as long as they want!

Nick, speaking of gurneys, have you noticed the massive unruly ones on this year's cars? They must now meet the ECE pedestrian safety requirement of R2.5 min, so on a parallel surface edge that's 5mm thickness...

[NickRally]

Hi Revman,

1) Yes, roof vent (bit of a misnomer) for cockpit ventilation.
2) Teams run a pre-event test in representative terrain/surface before each rally, which is where the baseline setup of the cars are determined. Throughout the weekend, the crew (driver/codriver) can and do constantly make adjustments to the dampers, ride height, etc. as the conditions change. The race team/engineers are all involved in this together of course.
3) "Freeze" might be too strong a word here. Yes, the regulation which came into effect this year stays until (at least) 2019. Teams must homologate certain parts of engine, suspension, chassis, hydraulics and bodywork, and they are indeed "frozen". We are allowed a number of "jokers" to spend, i.e. make modifications to homologated parts. Some parts are homologated as options, so different types can be introduced throughout the year. Other parts are completely free in terms of development. So it's not a development war, but not completely restricted either.
4) $900k is a very conservative number ;) I myself still can't fully make sense of the economic side of things, I just hope every team has deep pockets and everyone can race as long as they want!

Nick, speaking of gurneys, have you noticed the massive unruly ones on this year's cars? They must now meet the ECE pedestrian safety requirement of R2.5 min, so on a parallel surface edge that's 5mm thickness...

Once again very helpful insight. Also very interesting what you are saying about the gurneys - should we assume the same applies to the wing trailing edges? And even more to the point, presumably the edges can't be left square, but must be radiused with R2.5? This will straighten the hair of any F1 aerodynamicist :)

And one more question - you are saying "Throughout the weekend, the crew (driver/codriver) can and do constantly make adjustments to the dampers, ride height, etc." - how do they adjust the ride height? This must involve some fairly hard work assuming you are not allowed to do it from the cockpit?

[Mirek]

I don't know if it's same with the latest WRC cars but with R5 You can move the lower spring platform.


Teams must homologate certain parts of engine, suspension, chassis, hydraulics and bodywork, and they are indeed "frozen".

Is the damper internal structure still free?

[NickRally]

I don't know if it's same with the latest WRC cars but with R5 You can move the lower spring platform.



Thanks Mirek, so hard working it is then.

[Revman]

Hi Revman,

1) Yes, roof vent (bit of a misnomer) for cockpit ventilation.
2) Teams run a pre-event test in representative terrain/surface before each rally, which is where the baseline setup of the cars are determined. Throughout the weekend, the crew (driver/codriver) can and do constantly make adjustments to the dampers, ride height, etc. as the conditions change. The race team/engineers are all involved in this together of course.
3) "Freeze" might be too strong a word here. Yes, the regulation which came into effect this year stays until (at least) 2019. Teams must homologate certain parts of engine, suspension, chassis, hydraulics and bodywork, and they are indeed "frozen". We are allowed a number of "jokers" to spend, i.e. make modifications to homologated parts. Some parts are homologated as options, so different types can be introduced throughout the year. Other parts are completely free in terms of development. So it's not a development war, but not completely restricted either.
4) $900k is a very conservative number ;) I myself still can't fully make sense of the economic side of things, I just hope every team has deep pockets and everyone can race as long as they want!

Nick, speaking of gurneys, have you noticed the massive unruly ones on this year's cars? They must now meet the ECE pedestrian safety requirement of R2.5 min, so on a parallel surface edge that's 5mm thickness...

Thank you so much! What a fabulous sport!

[GigiGalliNo1]

I'm enjoying this thread, very professional and serious for this forum. Thank you.

[AMSS]

[QUOTE=Mirek;1145988]I don't know if it's same with the latest WRC cars but with R5 You can move the lower spring platform.

Mrpengski surely knows better how it is today but at least on previous WRC generation you could adjust the ride hight hydraulically from the boot/engine compartment limited times via a pressure ackumulator(once pressure was used than back to mechanic adjustment)
Same thing damper internals were completely free.
But it would be interesting to know if there are changes to the rules in current WRC generation?

[sonnybobiche]

MrPengski, can you clarify for us whether there were some last minute regulation changes to ban those sweet two-element wing mirrors that Toyota were using? I noticed they were used in testing and were present on the launch car but were gone by Monte, replaced with a much simpler design. Also read an interview with Makkinen where he alluded to some last minute aero reg changes that pissed him off and cost like $60,000 to redesign around them, but he didn't specify what it was.

[Mrpengski]

Damper internals - no change from previous regulation as far as I know.

What could have happened with the mirrors (I don't know for certain) is that the FIA said not allowed, end of story. Simply put, a mirror is a device to give rearward visibility, and technically is not allowed to be or do anything else. I think it's a very different approach compared to F1 (definitely) and other series (probably), and we can push the rules a bit but not too much.

TM could be talking about the side impact regulation. As you may have noticed, most team's first test car was without the extra protection. The problem is, by adding some ~100mm to the door, you need to redesign pretty much the whole aero package. To start, the rear fender/door definitely has to change, then you must consider its effect on the rear wing and try to balance that with new front aero. Or it could be the rear wing, you can see the original version on their first test car (shall we say, "Ford style") versus the current one.

[dimviii]

https://www.youtube.com/watch?v=ftE2S509__E

[Sulland]

Does the tech level of the 2017 generation car mean that privat teams are history?

- general high tech level, little training for the privat engineers, hard to understand without background info
- more software, where the privateers are not allowed latest version
- suspension and dampers where you will not get latest update, or get to know news/ discoveries from manufacturer
- less testing opportunities if the privateers can afford it
- probably more issues giving the privateer drivers no real chance to compete on level ground, so no more may the best man win!

So this generation cars is the final nail in the coffin for privateers at top level in rally?

Too bad really, and mean that FIA has finally potty trained the bohemian of motorsport.

RallyCross is still a place you can build a winning car in your garage - but for how long.......

[AnttiL]

So this generation cars is the final nail in the coffin for privateers at top level in rally?

Basically FIA already decides who is good enough to drive a WRC2017 car and only factory teams can enter WRC2017 cars. Østberg has been entered by M-Sport in all events.

[janvanvurpa]

Does the tech level of the 2017 generation car mean that privat teams are history?

- general high tech level, little training for the privat engineers, hard to understand without background info
- more software, where the privateers are not allowed latest version
- suspension and dampers where you will not get latest update, or get to know news/ discoveries from manufacturer
- less testing opportunities if the privateers can afford it
- probably more issues giving the privateer drivers no real chance to compete on level ground, so no more may the best man win!

So this generation cars is the final nail in the coffin for privateers at top level in rally?

Too bad really, and mean that FIA has finally potty trained the bohemian of motorsport.

RallyCross is still a place you can build a winning car in your garage - but for how long.......


No no no tjurskalle! You misunderstand everything.
It means whoever wins is THE BEST DRIVER.

I still don't understand why some people have to confuse things by introducing facts and reasoning to the discussion...

Stygging!:arrows:

[KKS]

Basically FIA already decides who is good enough to drive a WRC2017 car and only factory teams can enter WRC2017 cars. Østberg has been entered by M-Sport in all events.
only for 2017 year

[AnttiL]

only for 2017 year

Next year it's gonna be normal again? I didn't know...

[mknight]

Does the tech level of the 2017 generation car mean that privat teams are history?


When was the last time a "real" private team was very competitive?

Maybe Solberg with C4.. but was it all that private? Also it was at the end of C4 development, so there was not so much new coming for factory cars. Even less sure about his DS3 time. Most of M-Sports cars are always half-factory, depending on how much people pay.

The point about C4 development applies also now, with new cars the factor teams are introducing rather big changes as often as possible now. When the current generation is more mature and/or nearing a bigger rule change it's more likely that "privateer" cars are more similar. But yes at the start of the year Østberg's car was prbly same as others, but then the differences started to increase.

[br21]

It's all about money. If you have enough you can have best people, almost best/latest parts from factory and some own developed stuff (i.e. dampers), a lot of tests, etc. But the level of money needed for 2017 car is so high that it's hard to afford.
Currently in Rallycross on World Champs level it's impossible to compete with car build in garage. Level of top cars is super high.

[Revman]

NEWBIE ALERT!!!! Are the vents in the hood/front quarter panels for brake cooling? I would assume that the turbo intake would be through the "grill?"

Additional question about braking.....Brembo talks on their website about their levels of support for teams. They refer to Toyota as only using some components. What can you tell me about these various levels of support? Do teams draw from other suppliers for some components? Propriety stuff? How does all of this work?

[OHL]

NEWBIE ALERT!!!! Are the vents in the hood/front quarter panels for brake cooling? I would assume that the turbo intake would be through the "grill?"

Additional question about braking.....Brembo talks on their website about their levels of support for teams. They refer to Toyota as only using some components. What can you tell me about these various levels of support? Do teams draw from other suppliers for some components? Propriety stuff? How does all of this work?

Brake cooling air is mostly taken from the front bumper for the front brakes.
The vents that you see in the hood are there to evacuate air that has passed through the various coolers in the front of the car. Air going in the front bumper then passes through the Radiator(s), Intercooler(s), Gearbox Oil Cooler(s), Power Steering Cooler(s), etc. then out through the vents in the hood. The turbo intake is also usually through the front bumper.

Air management through the front of the car is something that takes a lot of clever thinking and hours and hours of testing and design revisions. The air hitting the front of the car is both a blessing and a curse. It can cool, create downforce, cause drag and create lift all at the same time. How you manage it is the key. The are myriads of little splitters, ducts, guidevanes, block-off plates etc. all doing their part to help manage the air flow to get the desired benefit.

[Revman]

Brake cooling air is mostly taken from the front bumper for the front brakes.
The vents that you see in the hood are there to evacuate air that has passed through the various coolers in the front of the car. Air going in the front bumper then passes through the Radiator(s), Intercooler(s), Gearbox Oil Cooler(s), Power Steering Cooler(s), etc. then out through the vents in the hood. The turbo intake is also usually through the front bumper.

Air management through the front of the car is something that takes a lot of clever thinking and hours and hours of testing and design revisions. The air hitting the front of the car is both a blessing and a curse. It can cool, create downforce, cause drag and create lift all at the same time. How you manage it is the key. The are myriads of little splitters, ducts, guidevanes, block-off plates etc. all doing their part to help manage the air flow to get the desired benefit.

Thank you very much.

[Mrpengski]

Poor person's flow-viz. Take your pick.

Water:
https://www.ewrc.cz/images/2017/photos/ypf_rally_argentina_2017/mes_argentina_09.jpg

Dirt (this one is really good):
https://www.ewrc.cz/images/2017/photos/rally_italia_sardegna_2017/dwi_17-07ita_paddon0015.jpg

Snow (not through the engine bay, but still interesting):
https://www.ewrc.cz/images/2017/photos/rally_sweden_2017/sno_081.jpg

This year's splitter is helping a lot to keep water away from the inlet area in a watersplash. But as we saw in Monte, Sweden and other gravel rallies, it's also very good at scooping up dirt and snow. I'm looking forward to Spain. If we have gravel conditions anything like last year, it would be very interesting (and demanding).

[NickRally]

Watching Rally Finland SS1 and it is incredible to see how flexible the Citroen diffuser streaks are (topic discussed previously), flapping about a lot, good views at 17:17, 26:17 and 33:40.

[mknight]

Yeah, can't they be changed for different rallies? In a "smooth" gravel rally one could use stiffer ones without fear of breaking them.

[NickRally]

Yeah, can't they be changed for different rallies? In a "smooth" gravel rally one could use stiffer ones without fear of breaking them.

I wouldn't be surprised if the answer to this question is no due to the homologation regulations.

[NickRally]

Hi boys and girls, haven’t been able to post in a very long time, but was able to enjoy Rally Germany and was happy to see that the doom and gloom predictions for a dull 2017 course proved to be very wide of the mark with some very challenging sections in the “country” lanes.
The topic I would like to pick up now is the discussion about the airborne behavior of the Citroens. First let me say that I am in the camp that thinks the cause of the nose up attitude is in what happens prior and during the jump mechanically rather than aerodynamically, so it will appear as though I am biased in the “logic” below, but I will give it a go and try to be as objective as the facts (or lack of :)) in my possession allow.
What I did was to watch several times few on-boards and also the SS21 re-play around the jump in question (the jump just prior to the finish), while timing the events and noting the velocities and engine rpm involved. My primary objective was Breen’s car and as a result, and taking worst case scenario (worst case scenario from calculations point of view that is, otherwise most optimistic from point of view of supporting the idea that aero imbalance is the culprit for the nose ups), I would say the elapsed time from the start of the jump to the peak is around 0.4s-0.5s, so let’s say 0.5s (remember worst case for calcs).
Unfortunately car speed and engine rpm data for Breen on SS21 was corrupted and no use, but looking at some of the other cars and taking worst case, I would say his speed at the point of the jump was 140kph. At the same time, re-playing the stage from the outside, I would say the max nose up angle in the air was around 7.5deg – this means that for the aforementioned 0.5s, the car has rotated 7.5deg (I know few assumptions involved, but that is unavoidable) – this would suggest angular acceleration of 60deg/s2 or using more appropriate term ~1.05rad/s2, let’s round this down to 1rad/s2. What I also did was to estimate the polar moment of inertia of the car around the horizontal transverse axis by doing some sketching and assuming 1375kg weight with around 2500mm-2550mm wheelbase – I reckon this number is around 1600kgxm2 (but maybe people with experience of modern rally cars like Mirek can correct me). The combination of angular acceleration and polar moment of inertia above, results in the requirement for 1600Nm of rolling moment. Now, assuming 50/50 weight distribution, that would require for the aero imbalance to be in the order of ~125kg minimum, i.e. at 140kph the rear axle aero load to be 125kg greater than the one acting on the front axle. Such aero imbalance for a roughly 50/50 weight distribution car, would make handling really impossible, but before anybody jumps and says “Citroen’s it obviously is”, it would make it impossible in the opposite way to what the drivers have been commenting (nervous rear). Nevertheless, let’s keep this thread - considering that at 140kph, the total downforce is unlikely to be more than, let’s say 225kg for simplicity’s sake (even that is probably gross overestimate and when running close to the road at that, i.e. not in the air), than the above imbalance requirement would mean front/rear aero load of 50kg/175kg, i.e. understeer nightmare of a rally car, which to my mind suggest that the combination of road profile, suspension settings and driver actions prior to the jump is more at play than aero forces. Also comparing Mikkelsen’s car in the same jump to Breen’s, it did not display any of the nose up characteristics, most likely because he braked heavily prior to the jump, something that Breen does not appear to have done. Also during the jump, Breen’s engine rpm first went significantly up, then he lifted which brought them down, which means engine inertia reaction moments will try to roll the car (people with knowledge can comment which way the crankshaft rotates to enable us resolve which way the car should roll when rpm goes up and down).
Having said all that, any mechanically/driver induced rolling nose up motion will then result in the flat-ish floor of the car turning into massive lift generating device leading to even more nose up attitude. Of course it is also possible to argue that aero imbalance prior to the jump causes a small nose up roll, which then results in further roll when the car is in the air, but I am of the believe that such aero imbalance will be heavily felt by the driver handling-wise, while also in Citroen’s case, taking into account their issues of nervous rear, I reckon it is very unlikely they have hugely more rear than front downforce, especially considering the flappy diffuser strakes, which probably render the rear diffuser useless. And the other thing is that watching the on-boards from several cars at this jump, the drivers treated the approach differently, which then affects the behaviour in the air significantly.
Thanks to anybody that had the patience to read this and apologies for any typos as I haven’t got much time to check it properly :).

[SubaruNorway]

Has nothing to do with aero more so with weight ballast placement.....

If it was that easy we wouldn't see it with three rounds left, it has everything to do with aero. And why don't see people so much on the rev limiter on big jumps because they need to compensate, it's the force of the wheels that controls the angel in the air not the crank really, same in Motocross. I can even feel it on my downhill bike if i look the rear brake mid air it tips forward.

[Sulland]

If only weight/ballast distribution, why not fix it?
I think it is deeper than that.

[itix]

Also during the jump, Breen’s engine rpm first went significantly up, then he lifted which brought them down, which means engine inertia reaction moments will try to roll the car (people with knowledge can comment which way the crankshaft rotates to enable us resolve which way the car should roll when rpm goes up and down).
Having said all that, any mechanically/driver induced rolling nose up motion will then result in the flat-ish floor of the car turning into massive lift generating device leading to even more nose up attitude. Of course it is also possible to argue that aero imbalance prior to the jump causes a small nose up roll, which then results in further roll when the car is in the air, but I am of the believe that such aero imbalance will be heavily felt by the driver handling-wise, while also in Citroen’s case, taking into account their issues of nervous rear, I reckon it is very unlikely they have hugely more rear than front downforce, especially considering the flappy diffuser strakes, which probably render the rear diffuser useless. And the other thing is that watching the on-boards from several cars at this jump, the drivers treated the approach differently, which then affects the behaviour in the air significantly.
Thanks to anybody that had the patience to read this and apologies for any typos as I haven’t got much time to check it properly :).

I agree with your analysis regarding aero, but I wonder about the engine inertia rotating the car (it's probably a factor but the rotating assembly doesn't weigh a lot). In my head it makes more sense that the rear wheels which broke traction from the ground the last was what caused the rotation. If he had lifted before the jump it would likely have had a very different outcome.

We've had famous backwards rotations before, like Novikov in finland a few years back and that was with the old C4 which obviously had good balanced downforce.

If you brake at the crest, the nose should want to come down, if you accelerate, the nose should want to go up as I imagine it.

[itix]

I have a question about suspension setup. Does anyone know whether there are regulations concerning the suspension setup you use? Does it have to be McPhearson like the road car or would the regs allow you to change it to a double wishbone configuration? If I remember well, some group B cars had double wishbones.

I am not sure what would be ideal for performance but in my mind the increased unsprung weight of two wishbones would likely have a negative impact and the neutral camber can't in my mind offset that... anyway, just curious how liberal the regs are.

[Mirek]

Yes, McPherson is mandatory or at least it was until 2016. Now I'm not totally sure but since every team uses it I guess it still is.

[AMSS]

Regarding the subject, last year PSRX experimented with both Mcpherson and double wishbones in WRX but from my understanding they ended up using Mcpherson after several tests.

[SubaruNorway]

Regarding the subject, last year PSRX experimented with both Mcpherson and double wishbones in WRX but from my understanding they ended up using Mcpherson after several tests.

Hoonigan Racing is using double wishbone, stronger and doesn't change the alignment as much

[AMSS]

Hoonigan Racing is using double wishbone, stronger and doesn't change the alignment as much

Yes and if I remember correctly this was the reason also PSRX tested it, I can be wrong though..

[itix]

Hoonigan Racing is using double wishbone, stronger and doesn't change the alignment as muchYeah but the unsprung weight is bigger meaning that the suspension is slower to react to changes. Sure it's probably stronger in case of a side impact on the wheel and sure, the camber stay the same even when when the suspension is compressed but does this really mean so a lot in rallying or rally cross? I doubt it. On a smooth flat definitely... Dirt and rough asphalt... Probably not.

If they experimented with it I am sure they had a good reason though. I don't follow rallycross closely but I seem to recall that Hoonigan were doing quite well.

[Mirek]

IMO the advantage of keeping the camber is more of an advantage in off road races where there is a need of good traction even with rather extreme positions of wheels. On the other hand these cars have usually huge wheels so they don't need to care about small bumps/holes unlike WRC cars with rather small diameter of wheels. Those huge wheels are also heavy so the weight of suspension alone doesn't play that big role.

Double wishbone shall be better for heavy braking as well and as it was already said it's more robust and can take more beating.

IMO there is another advantage of double wishbone and that's freedom of setting the castor. With usual McPherson setup there are massive forces in the steering coming from huge castor (angled strut) and with that more reliability problems appear.

Take is as an amateur talk anyway ;)

[itix]

Take is as an amateur talk anyway ;)

If we knew what we were talking about on a truly professional level, we'd be working for one of the teams by now ;)

Pardon my ignorance but how can the caster angle cause forces? I know that the caster determine lift of the body when the wheel is turned (so a heavy landing with the wheels sideways would snap the steering out of your hands... But i think the car would flip before that tbh).

If the scrub radius was large I'd understand it... You'd feel every little bump twisting the wheel out of your hands... But caster?

[Mirek]

You said it - the bigger the castor the more you lift the heavy body when You turn the steering wheel. The power steering unit has to generate the force needed to lift the body and the whole steering assembly has to wistand these big forces.

[mknight]

Probably a stupid question but doesn't McPherson allow longer max. travel than double wishbone for given size/weight?

[dimviii]

Probably a stupid question but doesn't McPherson allow longer max. travel than double wishbone for given size/weight?

yes.

[itix]

Probably a stupid question but doesn't McPherson allow longer max. travel than double wishbone for given size/weight?Depends on where you attach the the suspension strut.

Not necessarily actually. A lot of desert buggys and such have super long travel suspension.
https://images.fineartamerica.com/images-medium-large/desert-buggy-paul-svensen.jpg

Edit: or maybe you meant for any given length of the wishbone/control arm. That i can't be sure of, but I'm still not convinced. Theoretically you should be able to manage the same angle of the strut even if you have two suspension arms.

[mknight]

The wishbones on that buggy are half the width of the car. So yes that's what I meant. You can have as much travel, but it will take much more space.
On McPherson suspension the only thing that will need to be long/extendable is the track control arm no? One "thin" arm that is on the bottom of the car.

[itix]

The wishbones on that buggy are half the width of the car. So yes that's what I meant. You can have as much travel, but it will take much more space.
On McPherson suspension the only thing that will need to be long/extendable is the track control arm no? One "thin" arm that is on the bottom of the car.Well unless you design an A-arm with extremely wide cross section at the upper upright link (where the upright or knuckle or hub meets the control arm/A-arm) you can still fit the strut at the same angle. And the attachment point of the strut is lower so for any given space you can attach a longer strut.

http://120.img.pp.sohu.com/images/blog/2007/11/7/10/2/116b37a5c76.jpg

[mknight]

Well I know very little about suspension but in a simple hypothetical example:
- with McPherson you can have the control arm horizontal in the uppermost position and make it half the width of the car. (since it's on the bottom). That gives massive travel (with massive camber change) and there is still a lot of space between the wheels (for engine, cooling etc.)
- if you want to have as much travel with double wishbone the upper wishbone needs to extend also half the width of the car. Even if the vertical distance between the two wishbones is low it will eat up space between the wheels. (Angling the dampers inwards to give extra space for the upper wishbone also eats space.)

Or is there something I am missing?

[itix]

Well I know very little about suspension but in a simple hypothetical example:
- with McPherson you can have the control arm horizontal in the uppermost position and make it half the width of the car. (since it's on the bottom). That gives massive travel (with massive camber change) and there is still a lot of space between the wheels (for engine, cooling etc.)
- if you want to have as much travel with double wishbone the upper wishbone needs to extend also half the width of the car. Even if the vertical distance between the two wishbones is low it will eat up space between the wheels. (Angling the dampers inwards to give extra space for the upper wishbone also eats space.)

Or is there something I am missing?You are absolutely right that they would take more space Since McPherson can be made quite narrow and allow a relatively large engine bay.

The upper control arm does not actually have to be the same length as the lower one (and isn't really on a lot of applications).

I imagine the Hoonigan rally cross team are using the fact that the engine is mid mounted to enable them to use the space where the engine would sit on a normal rally car. If you tried to mount this in a regular shock tower without major modifications to the engine bay the control arm would be so short that the camber would change dramatically (unless you pair the lower one to the same length but then you would have massive track width changes and veeeery likely clearance issues, ie like you said... Not as much travel).

If you want to build a double wishbone rally car with a transverse layout like the modern rally cars, you'd have to make major modifications to the engine bay and shock towers to accommodate an upper control arm long enough.

Not very practical or desirable I imagine.

[Mirek]

Exactly, You need mid-engine car to have so big suspension travel with double wishbone.

[NickRally]

Itix and Mirek - good assessment of the pros and cons of the double wishbone vs Macpherson strut suspensions.
Given sufficient space and provided it is allowed by the regs (i.e. car does not have to be based on one using Macpherson strut), the double wishbone suspension will offer the most versatility in kinematics parameters coupled with good installation stiffness and offering lower weight relative to other systems for the same installation stiffness.
Having said that, the Macpherson strut is a very good system and has been successfully used in the past on race/rally cars that have not been constrained to it, with examples from Lancia coming to mind (Beta Montecarlo Turbo front and rear and Stratos rear).

[janvanvurpa]

Well maybe as somebody who has been working on and modifying suspension on competition vehicles since fall 1973, diassembling and modifying valving internally since winter 1976, and manufacturing suspension since 2003...One serious thing about MacPherson stuff I learned from a Ford engineer in UK whose very first job at Ford when he was first day at Ford was working with Mr Macpherson was this: he said the No1 priority was "acceptable design with eye on production line assembly time.."
This was early 1950s..He said "It was only much later when we had been rallying the escorts for some time that we saw a second major advantage and that was that we were feeding all the suspension loads into widely different areas of the bodyshell" and that the result being that those areas did not have to be excessively heavy.

This was of course a much larger issue when there was some connection between a rally car and something made by a car manufacturer---as was the case under Groups 1, 2, 4, A and N...before the "Whirled Rally Car" rules allowed total divorce from reality...

The fact that all strut designs sees the camber changes drastically and that the tire contact "rolls" all over the place seems to be a shocking side effect and one which is clearly worse as travel goes up......but the obvious increases in speed means if I'm shocked its because its a "theoretical" bad thing but in real life its not nearly as important as the increased travel and the resulting compliance and ability to put power down on acceleration and maintain contact during braking..

In that respect its just the same advantage/disadvantage calculations we faced on moto-cross bikes 30 years ago when we got the same sort of travel the cars have had in recent length...That acc and braking advantage was more valuable that the loss of precision turning was a disadvantage.
The modern strut is a pretty amazing design but personally I still have to giggle a bit that it took almost 25 years to get them to the travel we had so long ago.

[NickRally]

All good points Jan.
On another note, although probably nobody cares, but to correct myself, I mentioned the Beta Montecarlo Turbo as not being constrained to the use of Macpherson strut suspension after making the assumption that the Group 5 cars were pure silhouette racers, but then started having some doubts about that and a quick internet search on the former FIA technical rules ( argent.fia.com/web/fia-public.nsf/whistj?open ) proved that assumptions wrong and revealed that the suspension type of the base car had to be retained. So that leaves the Stratos as the only high level competition car in the more recent history, that comes to my mind at least, that was designed from the ground up with Macpherson strut suspension in mind (using one at the rear).

[janvanvurpa]

..... So that leaves the Stratos as the only high level competition car in the more recent history, that comes to my mind at least, that was designed from the ground up with Macpherson strut suspension in mind (using one at the rear).

As a formerly active rally driver of a car the highlighted bits mildly put confuse the fuq out of me> .
I belive that in this sport--and that IS what this forum is all about, the overwhelming majority of high level competition cars in the last 50 years have been strut cars and the number of cars with double a arms exceedingly small....Very short list really of non-strut cars..
Clearly there is confusion about what you mean by "high level", and also "competition car"..

My own car was double A arm..and a car with same everything but cylinder bore won a WRC round for decade till the final time in Feb 1976....Opel Ascona B, they did goos as did all the Group b cars except Audi, but that's just a few cars..

EVERYTHING else has been struts..
So again, wot da fuq?

[NickRally]

Hi Jan, no need to shout, I am very happy to clarify what I meant - you quoted the last 50 years - would you list all the rally cars that have been designed from the ground up as rally cars, i.e. not based on production cars, that have employed the Macpherson strut? I do not pretend to know the complete rally history and with my limited knowledge of the world, I am happy to admit that the only one that comes to my mind is Lancia Stratos rear suspension, but that's why we have this forum where everyone can contribute, enriching the knowledge of the others. So, yes please, I will be happy to learn more regarding the above question.

[Lundefaret]

Hi Jan, no need to shout, I am very happy to clarify what I meant - you quoted the last 50 years - would you list all the rally cars that have been designed from the ground up as rally cars, i.e. not based on production cars, that have employed the Macpherson strut? I do not pretend to know the complete rally history and with my limited knowledge of the world, I am happy to admit that the only one that comes to my mind is Lancia Stratos rear suspension, but that's why we have this forum where everyone can contribute, enriching the knowledge of the others. So, yes please, I will be happy to learn more regarding the above question.

This is a question of definition?

How many cars has there been that has been designed from the ground up to be a rally car?

Lancia Stratos

Ford RS 200 (double A Arm)

Renault 5 Turbo (double A Arm) (since this is a version of the Renault 5, this is open for discussion)

We also have the other group B cars (except Audi Sport quattro in all its versions, and the Citroën BX), but they were all at least made to look like production relatives (Pug 205, Lancia S4, MG 6R4) which put constraints on their design).

Worth mentioning is the Audi Group S, but it never raced (all other Group S prototypes were also designer with an eye on a production car, inc the Lancia Delta, the Opel Kadett, the Toyota MR2, the Lada etc.

I may be forgetting some cars - please feel free to contribute :)

[janvanvurpa]

Hi Jan, no need to shout, I am very happy to clarify what I meant - you quoted the last 50 years - would you list all the rally cars that have been designed from the ground up as rally cars, i.e. not based on production cars, that have employed the Macpherson strut? I do not pretend to know the complete rally history and with my limited knowledge of the world, I am happy to admit that the only one that comes to my mind is Lancia Stratos rear suspension, but that's why we have this forum where everyone can contribute, enriching the knowledge of the others. So, yes please, I will be happy to learn more regarding the above question.

I was not shouting, merely trying to use color and italics to give tone to the specific part of what you were saying that I was baffled about..In speech we can use tone--rising inflection or a raised eyebrow...
Rally has thru time for most people always been based on road going cars*, hence the minimums needed to qualify for homologation in the 5000 or 2500 range (excpet the baddest of the Group 4 cars at 400 units and group B at 200 units....And post 1968 most cars were struts on front in term of models and numbers made..
Group 4 Escort, widely acknowledged as the coolest car in all human history, and Fiat 131 were high performance competition cars.. Sierra Coswoth, all the Lancia Delta Intergrales were high performance competition cars.
as were all the Group A Gaylants, Legacys, Lancer Evos, Imprezas and ALL the World Rally cars ...
The sticking point was the phrase "designed from the ground up"

[NickRally]

Thanks Jan, I am aware of these facts and vehicles. To clarify what I meant by “from the ground up”, for me it is when the designers are given “clean sheet of paper” (or a “blank screen” these days) to design the best possible car within the constraints of the rules, without having to base their designs on existing vehicles. I have been designing racing cars for a living for 20 years now and certainly appreciate when I have the freedom to do so (which for me is actually most of the time :)).
The cars that fit the above description, that I know about, are not that many – Stratos, 037 (for the most part), RS200, Audi Group S, ECV 2, Moskvich Gr.B/S – from these, as far as I am aware (but happy to be corrected), only the Stratos designers opted for Mcpherson strut suspension (at the rear).
Most of the other extreme Gr.B cars had to observe the silhouette of the original car they were supposed to promote and as such it sometimes meant not enough packaging space for the designers to have a completely unrestricted choice of suspension type (as was the case with Metro 6R4), while others had enough space to fit double wishbone suspensions.
Talking about the Stratos, I suspect the reason for the strut suspension was still the lack of packaging space, but it was the choice of the designers to implement a transverse engine and a short wheelbase concept restricting the available volume.
As far as I remember (without going through all the posts), the original discussion about the Macpherson strut suspension started with itix asking if Macpherson strut is there because of the tech regs and also pondering the pros and cons of the Macpherson strut vs double wishbone suspension and which one would allow for better performance. We settled on the fact that the Macpherson strut is prescribed by the regs (and it would appear that way when reading them), but even if it wasn’t, it still offered the best choice due to the constraints coming from the overall packaging of the current WRC cars, which are still based on production layouts. At this point, I started wondering if there were any examples where the designers were allowed to choose what they want (either by the marketing departments/accountants or by the regs), but had still opted for the Macpherson strut suspension, and the only vehicle I could think of was the Stratos, which once again was most likely the result of choosing transverse engine and short wheel base concept in the first place.

[AnttiL]

Chris Williams, the Chief Rally Engineer at M-Sport talks about the 2017 regulations and how things have gone so far.

https://rallysportmag.com/feature-living-2017-world-rally-car-regulations/

[mknight]

Interesting points from my view:

“Some teams have gone full on in every area of design and pushed into areas thought were out of bounds. Others have been more conservative and have not exploited some of the new freedoms to the maximum."

With my limited knowledge I see 2 main areas where some cars are pushing the limits:

- Citroen with different damper mountings for Gravel/Tarmac
- Toyota with the extensive rear aero going "into" the bodywork instead of just wheelarches

Anyone else has other candidates?


"But going forward now it is harder to find extra performance. You could spend a lot of money analysing what everybody else already has, compare it to what you have and implementing the best of both worlds. That’s actually quite an expensive project."

I'd guess this is one of the 2 main ways of going faster now. The other one is optimizing setup for different events.

"In areas where teams have concentrated their test work in the past they may excel."

Clearly this holds more than ever with new cars that some teams have not really tested on specific roads while others test all the time there. (ref. Toyota in Finland/Sweden roads, Citroen on smooth tarmac, probably M-Sport in GB).
In this comparison it will be interesting to see how Australia works out.


have there been any unexpected problems?

CW: We have seen a lot of damage to wheels this year.

First time I hear about this, something to do with extra speed + downforce in corners?

[AnttiL]

CW: We have seen a lot of damage to wheels this year.[/I][/b]

First time I hear about this, something to do with extra speed + downforce in corners?

And wider cars?

[mknight]

And wider cars?

In general that should contribute as well, but he says the issue first came up on pre-event test for Corsica.

Example vid from the test here: https://www.youtube.com/watch?v=Vx4lyg9V56Y

During a test on a road like that damage from touching rocks on the side of the road due to wider car shouldn't be the main factor. (as opposed to a narrow-road gravel rally, where wider car just doesn't fit no matter which line the driver takes)

For tarmac, that's valid provided you keep same distance from the walls and in cuts as before. If you don't it's more of a problem of the driver not used to the wider car than the car itself.

[racerx1979]

Toyota is using exotic materials for suspension components. Titanium, Magnesium and some crazy hardened steel (same stuff used by Porsche for GT3 crankshafts). The damper, hub and control arms on the Toyota's are insanely lightweight.

[br21]

I think what Mr. Williams was telling it was the wear of the tires, not the physical damage to the rims/tires. Big wear is because big downforce, so high corner speeds, good grip under braking plus extra power, plus few other things.

Titanium and magnesium are again allowed for 2017 WRC cars?!

[AMSS]

Toyota is using exotic materials for suspension components. Titanium, Magnesium and some crazy hardened steel (same stuff used by Porsche for GT3 crankshafts). The damper, hub and control arms on the Toyota's are insanely lightweight.

Are you sure? I don`t know the rules for the current WRC 17 spec cars exactly but at least for the previous generations both titanium and magnesium was prohibited, would be strange to allow it now when the cars got enough more expensive anyway..
But if they allow it again than sure why not

[racerx1979]

Are you sure? I don`t know the rules for the current WRC 17 spec cars exactly but at least for the previous generations both titanium and magnesium was prohibited, would be strange to allow it now when the cars got enough more expensive anyway..
But if they allow it again than sure why not

I do not think Ti is allowed for the control arms, but is allowed for certain components such as springs etc. The rules still restrict certain components to be made of a specific alloy.

[Mrpengski]

Ti is not allowed unless it is basically a sub-component of a catalogue part. Suspension components are not part of that.

Mg also not allowed other than the wheels.

[sonnybobiche]

How would the FIA be able to tell what material is being used without some destructive testing? Seems like it would be easy to hide, particularly bits that are hard to get to, e.g. buried deep in the engine.

[Antony Warmbold]

They wouldn't, but they sometimes act on tips and that's when they know exactly what to go look for.

[Mrpengski]

In case of the engine, it is disassembled to the last bolt and nut and each and every part is inspected and characterised in the homologation. And it can be checked to this level of detail at any point if requested. Same for suspension or any other parts worth using exotic material on, all are physically handled and any obvious ones would stand out to experienced inspectors.

But more to the point, if you think about it, it's the "obvious" major items where one can gain the most advantage by using fancy materials, so it's not hard to have in mind already the usual suspects. Saving fractions of grams by using Ti bolts in some hidden location, for example, is out of scope of WRC in my opinion (not yet anyway). If the rest of the car is so perfect that you're delving into such minute detail, then you should be winning the championship anyway.

[denkimi]

How would the FIA be able to tell what material is being used without some destructive testing? Seems like it would be easy to hide, particularly bits that are hard to get to, e.g. buried deep in the engine.
They can simply weigh it. A part that is said to be steel, but is made of titanium will have a different weight.

[AMSS]

Ti is not allowed unless it is basically a sub-component of a catalogue part. Suspension components are not part of that.

Mg also not allowed other than the wheels.

I don`t think they use Mg wheels however as there`s a minimum weight on the wheels, 8,6 kg (if it`s still the same s it used to be).

[Mrpengski]

I don't know if anyone is using it, but it's allowed.

[br21]

I'm pretty sure many teams use magnesium rims. At least many R5 teams use them. They are not super light as anyway there is minimum weight, but they are much stronger than alu.

[dimviii]

How have the new 2017 WRC cars affected tyre wear? Martin Holmes speaks to tyre consultant George Black to get the low-down.

https://rallysportmag.com/feature-world-rally-car-tyre-update/

[sonnybobiche]

Thanks to the crack journalists that cover the WRC, we literally just found out that there is another new regulation for this year: onboard tyre pressure monitoring.

[itix]

Thanks to the crack journalists that cover the WRC, we literally just found out that there is another new regulation for this year: onboard tyre pressure monitoring.Heard that on the radio today too.

Seriously, if WRC could get the technical journalism that F1 has... It is literally the only aspect of F1 that is better.

[TyPat107]

Was just watching a stage start and started to wonder, what changes in the engine mapping between road mode and stage mode to give such a different sound to the engine?

[dimviii]

Was just watching a stage start and started to wonder, what changes in the engine mapping between road mode and stage mode to give such a different sound to the engine?

its a completely different map ,very mild that don't stress the engine.

[AndyRAC]

Heard that on the radio today too.

Seriously, if WRC could get the technical journalism that F1 has... It is literally the only aspect of F1 that is better.

Have to agree with this; but not only F1; the GT/LMP Sportscars technical journalism is streets ahead as well.

They obviously think WRC fans aren't particularly interested in that side of the sport - or they themselves aren qualified to write about it.

[ESTR]

My opinion (and I'm not expert at all):

1. M-Sport Ford Fiesta WRC - Tehnical best car at the moment, handling maybe not.

2. Hyundai i20 Coupe WRC - Suspension worst of all (just a little impacts & huge damage) but fast car.

3. Toyota Yaris WRC - Tehnical problems still (Latvala's car), maybe best handling.

4. Citroen C3 WRC - Bumpy conditions = disaster. Dominant car on tarmac.

[quick]

Hyundai
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[Mrpengski]

Was just watching a stage start and started to wonder, what changes in the engine mapping between road mode and stage mode to give such a different sound to the engine?

The biggest difference in sound comes from the anti-lag system or ALS. Here, you can hear it activate on some cars before they rev up. https://www.youtube.com/watch?v=a5SjKyP3Wk0

[AnttiL]

My opinion (and I'm not expert at all):

1. M-Sport Ford Fiesta WRC - Tehnical best car at the moment, handling maybe not.

2. Hyundai i20 Coupe WRC - Suspension worst of all (just a little impacts & huge damage) but fast car.

3. Toyota Yaris WRC - Tehnical problems still (Latvala's car), maybe best handling.

4. Citroen C3 WRC - Bumpy conditions = disaster. Dominant car on tarmac.

Citroen is fast on tarmac, hard to handle on gravel
Toyota is fast on very fast roads (gravel or tarmac)
Hyundai is seems to be the best overall but they struggled a lot in Finland with the big jumps.
Ford is quite equal on all surfaces.

As far as reliability, I think Ford has had the least issues, but I'd have to make a list to be sure

[doubled1978]

Citroen is fast on tarmac, hard to handle on gravel
Toyota is fast on very fast roads (gravel or tarmac)
Hyundai is seems to be the best overall but they struggled a lot in Finland with the big jumps.
Ford is quite equal on all surfaces.

As far as reliability, I think Ford has had the least issues, but I'd have to make a list to be sure

For me.
FORD - Has developed into the best overall package at the minute, engine seems very strong.

HYUNDAI - Still pretty strong overall, but but a few cracks appearing (no pun intended). Understeer in high traction, weakness of castings to impacts.

TOYOTA - Best chassis, but the team is still learning event to event and the car isn't always on point at the beginning. Reliability still an issue.

CITROEN - Inconsistent, the best on smooth, high traction. Watching the live TV it is clear as day, it just turns a tighter line than the others and can be driven within itself. On low traction, bumpy surfaces its all over the place. Suspension seems the worst of all. I guess we will see in Wales/Australia if the recent testing has made some gains.

[AMSS]

For me.
FORD - Has developed into the best overall package at the minute, engine seems very strong.

HYUNDAI - Still pretty strong overall, but but a few cracks appearing (no pun intended). Understeer in high traction, weakness of castings to impacts.

TOYOTA - Best chassis, but the team is still learning event to event and the car isn't always on point at the beginning. Reliability still an issue.

CITROEN - Inconsistent, the best on smooth, high traction. Watching the live TV it is clear as day, it just turns a tighter line than the others and can be driven within itself. On low traction, bumpy surfaces its all over the place. Suspension seems the worst of all. I guess we will see in Wales/Australia if the recent testing has made some gains.

Agreed

Ford seems to be overall the easiest package with good reliability and no direct weaknesses in handling though it doesn`t shine either in any certain area it seems (or maybe slow technical gravel they have the best grip..), basically a championship winning car

Hyundai was the fastest car beginning of the season but seems Toyota and Ford have slightly pulled away, seems to have a strong engine.

Toyota seems to have a fast car with the best aerodynamics, maybe struggle a bit with the suspension on slow technical gravel and technical reliability needs improvement.

Citroen fastest on tarmac, gravel still a big question mark (bearing in mind Meeke had a very good starting position on Friday)

[EstWRC]

Regarding the gearbox issue that Tänak had. How big difference it is running with gravel gearbox instead of tarmac one on tarmac rally ? Is it a big disadvantage or not?

[AnttiL]

Regarding the gearbox issue that Tänak had. How big difference it is running with gravel gearbox instead of tarmac one on tarmac rally ? Is it a big disadvantage or not?

Probably just different gear ratios? It didn't seem to slow him down that much...

[AnttiL]

Looking back now, Hyundai seems to have a big history this season with suspension/steering failures from relatively minor collisions

Monte Carlo Neuville
Sweden Neuville
Argentina Sordo (fixed on the road)
Sardegna Paddon
Finland Paddon (hit the same stone as Tänak, who got away with just a puncture)
Finland Paddon (2nd day)
Germany Neuville
Spain Sordo
Spain Mikkelsen
Spain Neuville

The only other similar issues that come to mind are Østberg's suspension failures in Argentina and Sardegna, but I haven't watched the onboards to know how if he goes off or not, but I got the impression that his team has a weaker part or a part not changed as often as M-Sport. Lappi knocked the suspension in Poland but the most damage was to the engine (the same as Latvala in Spain?). Hänninen also did something similar in Finland but they were able to keep it together to service and didn't even slow down that much.

[Mirek]

Regarding the gearbox issue that Tänak had. How big difference it is running with gravel gearbox instead of tarmac one on tarmac rally ? Is it a big disadvantage or not?

IMO nobody of us can say how big handicap it is. Probably the main issue is that the center and front differentials are one unit with the gearbox (I think they are). At least front one is mechanical and since You can't open it You have to drive with wrong ramps in it. That means You have to change maps of the center one to somehow cope with it, i.e. it for sure isn't optimal.

[EstWRC]

Thanks like always mirek!

[dimviii]

IMO nobody of us can say how big handicap it is. Probably the main issue is that the center and front differentials are one unit with the gearbox (I think they are). At least front one is mechanical and since You can't open it You have to drive with wrong ramps in it. That means You have to change maps of the center one to somehow cope with it, i.e. it for sure isn't optimal.

that's exactly the problem,the diffs ramps and preloads,than the shorter gravel gear ratios.Gravel diffs are more ''tight''
considering that,Tanaks pace was excellent vs Ogier.

[racerx1979]

The time lost on high speed sections with lower gravel rations could be a big factor too.

Tanak did an amazing job.

[racerx1979]

A few images of the Yaris suspension set-up.

The control arms and subframes are works of art. Formed and welded components which are lightweight yet extremely strong.

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[NickRally]

Going back to the Hyundai upright failures and looking at them from structural point of view rather than drivers' errors, I was wondering where do the rules stand on MMC (metal matrix composites)? I haven't got the time to check, but won't be surprised if they are banned. Maybe Mrpengski can let us know.
I am only saying this to exclude the possibility that the usage of this low strain to failure high notch sensitive, but light and stiff material is the culprit, given that the failures occurred around the lower joint threaded area with the thread acting as a "notch".
Excluding this, I assume the uprights are machined from forged billets, then shot peened for better fatigue resistance, giving the surface its matt appearence.
The other option is that the uprights are made from extruded aluminium billet (or even worse, cast billet - very hard to believe), which will give lower structural properties.
Next questio is what kind of ali alloy as some of the high performance structural aluminium alloys can be low strain to failure high notch sensitive.
Final point - is Hyundai's structural "rock touch" load case, that the suspension components are designed to, severe enough to cope with the events encountered on the side of the road? It is a very fine balancing act between ending with not too heavy components and not too weak components.

[ESTR]

The question is: HOW DO THAT HYUNDAI of Neuville survive Argentina?? Germany and spain total disaster

[racerx1979]

The matte appearance from hard anodizing, not shot peening.

Not sure about Hyundai, but the Toyota hubs are forged monoblock body hubs (similar to AP uses for calipers). The other teams could possibly using billet hubs if not forged. Nobody would use cast alloy. MMC could be a possibility since a lot of the Manu's are using Pankl comoponents for suspension hubs, uprights etc and they use MMC for other racing forms. I'm not sure if MMC is allowed for WRC.

https://www.pankl.com/en/racing/drivetrain/technology-design/
https://www.pankl.com/en/racing/drivetrain/products/

[NickRally]

ESTR - very simple - the suspension did not see loads exceeding its envelope :)

racerx1979 - I would be very surprised if the colour comes from hard anodizing rather than shot peening. Structural ali alloys do not hard anodize well and any hard anodizing significantly reduces the fatigue properties, while hardly really contributing to making the alloy that hard, while shot peening increases significantly the fatigue properties, which is critical for a suspension upright.
MMC wise, I will have to dig into the rules and find out if it is allowed (bear in mind it is not allowed for uprights in F1 after 2009), unless someone with inside knowledge is able to comment what the rules say. Anyway, I would be very worried if I had to use MMC for suspension uprights on a rally car.

[racerx1979]

I know for a fact the TGR hubs are hard anodized after being cryo treated. Shot peening sometimes contaminates the surface.

Some of the other manu's hubs may be shot peened before being hard anodized, but they are not shot peened and then left uncoated. The images of the Toyota hubs I pictured above are hard anodized. Also, shot peening is fairly old-tech in the motorsport world. Laser peening is used companies such as Pankl and Arrow.


Shot peening of Al alloys is commonly performed on aircraft parts to be hard anodized. The shot peening induces residual compressive stresses to compensate for the decrease in fatigue life due to the relatively brittle anodic coating. Common applications are hydraulic cylinders and pistons. All shot peening residues are chemically removed prior to anodizing. – MIL-S-13165C, paragraph 3.3.10.2; MIL-P-81985, paragraph 3.5.2.1. Nitric acid-based solutions are used.

Some great reads if you're into Metallurgy.

Effect of Shot Peening Variables on Fatigue of Aluminum Forgings,” Metal Progress, v. 120, No.2, p. 33-35 (1981) and
Hard Anodic Coatings on Aluminum Alloys: Evaluation and Control of Porosity,” Metal Finishing, p. 19-24 (December 1992).

[racerx1979]

And another study from long ago which shows the benefits of shot peening and anodized coatings.

If you don't feel like reading the whole thing go to page 19.

http://dtic.mil/dtic/tr/fulltext/u2/a108869.pdf

[NickRally]

All good reads, thanks racerx1979.
For clarity I should point out that race car suspension component design is part of my daily job.
In general anodizing (either of the hard or decorative kind) is not a great practice for highly stressed suspension components and can do more harm than good for reasons already stated.
Also talking about billets, all machined uprights start from some sort of billet, which in itself can be forged (best for strength), extruded (most common) and cast (worst for strength). For obvious reasons the first two options are preferred for suspension components.

[racerx1979]

I also work on chassis components focusing on motorsport for over 12 years :). We use SolidWorks, CREO and Ansys for FEA.

I agree that most "highly" stressed components such as lower control arms are made of T45 or 4130 are not anodized because they are not made of aluminum :).

But we are talking about hubs here which are machined from 7075 and then anodized. Some lower control arms are also anodized depending on the application and loads. Scroll down to see the Evo X R4 arms which came in red anodized for the left side and blue anodized for the right side. Typical old school wrc style components.

Ever seen Ohlins, Proflex or EXT shock bodies and reservoirs?

They are always anodized if aluminum and almost always nickel plated if steel. That's the titanium color you usually see.

Just like this AP caliper
https://www.essexparts.com/cp8350-trailing-left-anodized

And some more info from Brembo talking about hard anodized calipers and showing the same gold color. Anytime you see this color its hard anodized.
https://www.youtube.com/watch?time_continue=27&v=VQdAnQ8GZlA

Sometimes its a clear anodize and the aluminum will have a shiny polished look. Take a look at the components on Miko's old car. Tons of anodized parts (goldish and titanium components) and note the shiny hub. If this was shot peened it would have a dull finish. It's actually clear anodized after being polished.

1417

Another hard anodized Subaru WRC machined hub.

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http://www.racetuners.com/shop/index.php?main_page=product_info&cPath=11&products_id=449

When using steel the components are nickel plated as shown here.
http://rallycarsforsale.net/ads/brand-new-s6-front-uprights-impreza-wrc/

Evo X R4 lower wishbone in red anodize.
http://www.mml-sports.com/index.php/mml-sports-online-shop/product/289-front-arm-assembly-lh

Evo X uprights hard anodized.
https://www.brypar.com/shop/prime-r/uprights/mitsubishi-lancer-evo-7-9-front-upright/

[NickRally]

Thanks racerx1979, I am happy to leave it at this.

[NickRally]

Went through the rules (or what is publicly available) and can't see a ban on MMC. Actually, as is usual, the rules are very badly written talking about where "composite material" is allowed, evidently only considering resin (or similarly) based composites here, but without clearly defining what constitutes "composite material" and as such leaves the door open for protests if a team decides to explore the use of MMC, although these can sometimes be more pain than gain.

[Mirek]

IMO it's more precisely described in homologation regulations.

[Mrpengski]

Well Nick, if Metal Matrix "Composite" is not a composite material, then what is? :) For once, the public copy of the regulation shows the same information as the working copy in this case:

https://www.fia.com/file/61689/download/17389?token=hVJqMBK-


The use of composite is allowed for the following parts:
 Timing cover
 Air filter box
 Air ducts for cooling (cockpit and boot (FR) / radiators / intercooler / engine auxiliaries / brakes)
 Homologated exterior bodywork parts (see article 902)
 Windscreen lower trim
 Door trims (FR)
 Dashboard (FR)
 Seats
 Supports and fixings fitted inside the cockpit (except seat brackets) and inside the rear boot
 Protection covers fitted inside cockpit and inside rear boot (FR)
 Foot rest for driver and codriver (FR)
 Console / support for switches…
 Steering wheel
 Heat shields
 Protections of the bodywork parts (side, floor, inner wheel arch)
 Leakproof box for fuel tank (see article 401) (FR)
 Underbody protections (see article 902)
 Mountings for front and rear bumpers
 Headlight units and tail light units
 Additional headlights housings (see article 503)
 Paddles for power assisted gearshift control
 Supports and fixings fitted inside the engine compartment (except engine / transmission supports)
 Discs for differentials
 Baffles fiited inside engine oil sump and transmission housing
 Fuel tank internals
 Engine parts: see HOMOLOGATION REGULATIONS FOR 1.6 TURBO ENGINES
 Electric connecting box
All composite material parts fitted directly on the engine (parts mentioned in Article 3) and the parts fitted in the cockpit or in the boot mentioned above (FR) must be made from fire‐
retardant material (seats and driver / codriver equipment / energy‐absorbing material: see FIA standarts). The external face of the part must have a V0 level of acceptance respecting
the "UL94" US standard (fire‐retardance capability).

Basically, this list precludes any meaningful use of MMC on these cars.

Somewhere in this discussion indeed lies the truth about the finish on the part. What can I say, it's painful to see all three cars go out with the same broken part (whatever the circumstances), and it's not the first time they failed this year...

[racerx1979]

Unfortunately a bad design can not be saved by a coating or process at the end of the day. If they had hub failures breaking the connection for the lower wishbone at the ballpoint for many rallies than its time to design a new hub. Or at lease revised the connection of the ball joint to hub. I bet they will do this moving forward.

On thing I noticed when looking at the pics was the diameter of the l tapered ball joint stud. It was unnecessarily huge in my opinion. Never see Any WRC cars use such a large stud. This could result to huge loads on the hub and also reduce the amount of thickness in that area due to space limitations. On most arms we’ve worked on we would use a 5/8 heim (rose) joint or 14 mm in metric. The Hyundai ball joint stud looks huge. Like 20 mm, but this could be the image being zoomed in. The shear loads on a 14/16 mm heim or rose joint is more than enough for lower control arms used in McPherson suspension. I bet they will also change mountings for the shock body and the shock top mounts as well because the loads are going straight up from the ball joint to the top mounts. I’ve been lucky enough to see Toyota, Ford and Citroen suspension components and in terms of design and tech (not strength) Toyota is above Citroen which is above Ford. Have no clue what Hyundai stuff looks like. They’re actually pretty good at keeping things behind the scenes :). Oh and the weight of the Toyota assemblies is incredibly light.

[quick]

In a wheel arch,some air ducts are closed. And what sensor behind the rear window?
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[sonnybobiche]

I would guess that those are reflectors for the timing beam. Someone correct me if I'm wrong.

[steve.mandzij]

So, does anybody have any insight as to why the Toyotas struggled so much in low traction?

Sent from my Pixel using Tapatalk

[macebig]

So, does anybody have any insight as to why the Toyotas struggled so much in low traction?

Sent from my Pixel using Tapatalk

They were claiming that they had a weight disadvantage due to the design of the rear wheel arches. The car was keeping mud there (allegedly 100+ kilos).

[pantealex]

So, does anybody have any insight as to why the Toyotas struggled so much in low traction?

Sent from my Pixel using Tapatalk

Biggest problem was that they did all testing in dry weather, it was +20 temperature when Lappi tested.
Rear of car is/was too heavy (because of up to 120kg of mud) and front of car was way too light, so no grip in front and car was not turning.

[Mirek]

More weight on the rear is bad for nearly everything but not for the traction, quite the opposite.

What Pantealex wrote seems to be plausible explanation to me.

[racerx1979]

Diff and suspension settings are also key. Also I'm not sure of the speeds at Wales, but aero would not play a huge role if it's mainly tight and slow.

Toyota will be changing their aero for 2018. I hear it is even more futuristic looking than the current car.

[AMSS]

Diff and suspension settings are also key. Also I'm not sure of the speeds at Wales, but aero would not play a huge role if it's mainly tight and slow.

Toyota will be changing their aero for 2018. I hear it is even more futuristic looking than the current car.

According to Mäkinen interview the aerodynamic changes aren`t dramatic but mostly for easier service (for instance current front bumper is a 1 piece damper and when the splitter brakes they have to change the whole bumper) so the new version will have a separately changable splitter.

[Munkvy]

Diff and suspension settings are also key. Also I'm not sure of the speeds at Wales, but aero would not play a huge role if it's mainly tight and slow.

Toyota will be changing their aero for 2018. I hear it is even more futuristic looking than the current car.

Wales is definitely not tight and slow, watch some of the many youtube videos and you will see they are often going quite quickly ;)

[AnttiL]

Wales is definitely not tight and slow, watch some of the many youtube videos and you will see they are often going quite quickly ;)

Evans' average speed in Wales was 103 km/h which is pretty average for a gravel rally. Finland was 126 km/h, Poland 116 km/h, Argentina 98 km/h, Portugal 94 km/h and Sardegna 91 km/h. Wales has fast sections, but also lots of tight hairpins.

[Mirek]

You don't need any aero in hairpins but You need it in fast sections. If a stage has a lot of slow points like hairpins and junctions and still has average speed over 100 km/h it's in fact pretty quick. The sections between those slow points have to be of much higher average speed than the stage as a whole.

[mknight]

Evans had covering plates on the wheelarches while Ogier and Tanak had them at least semi-open... why?

https://www.ewrc.cz/images/2017/photos/dayinsure_wales_rally_gb_2017/hfr_dsc_3899-edit.jpg
https://www.ewrc.cz/images/2017/photos/dayinsure_wales_rally_gb_2017/jpo_80000020-ogier-ndz.jpg

[rs7]

Now I noticed this too. In videos all the M-Sport cars have them open and then taped shut.
Maybe it has something to to with them collecting mud

[TyPat107]

I tried to look find the answer in this thread but didn’t see one.
Why are Toyota using 2 radiators? It looks like a radiator on either side of the intercooler.
https://uploads.tapatalk-cdn.com/20171116/db4dd52ea1cabef6a0458ec5f6590044.jpg

[sonnybobiche]

Is it possible that the Toyota suspension components are machined hollow and then filled with some sort of structural foam? I don't think that would technically be called a composite material, so it seems like it would be a way of getting some of those properties (lightness, rigidity) while avoiding the regulation.

[NickRally]

Is it possible that the Toyota suspension components are machined hollow and then filled with some sort of structural foam? I don't think that would technically be called a composite material, so it seems like it would be a way of getting some of those properties (lightness, rigidity) while avoiding the regulation.

From pure technical point of view (i.e. disregarding the tech regs), in theory yes, but in practice very unlikely, as the current state of the readily available structural foams is such that their stiffness is significantly lower than the steel that the wishbones are made from. Maybe if you were to use a 3D metal (i.e. steel) printed lattice attached to the inside of the wishbone skins, then you might be onto something.

[sonnybobiche]

I often wish I'd stayed in engineering school. I hate technical 'anoraks' but I do love technical things, like this thread.

[Revman]

Love this thread.....Looking forward to observations regarding the changes between the 2017 and 2018 cars. What are you guys seeing that a newbie heading into his second season of love for this sport should know? Who has made the most changes?