Technical Analysis: WRC Cars 2017

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".

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.

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Originally Posted by NickRally

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.

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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.

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.”

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 ;)

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

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.

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.

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Originally Posted by Mrpengski

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 ;)

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

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

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

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?" :)

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.

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?

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:

Attachment 1333

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

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

yes, homologation regulations will never be officialy published.

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?

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:

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Originally Posted by Mrpengski

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.
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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.

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Originally Posted by Lundefaret

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.

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

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:

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.

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

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Originally Posted by Sulland

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

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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.

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.

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Originally Posted by 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.

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

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

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Originally Posted by Sulland

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

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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.

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.

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Originally Posted by 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.

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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..

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Originally Posted by Sulland

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

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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.

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Originally Posted by AMSS

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..

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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?

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Originally Posted by Lundefaret

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?

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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.

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?

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Originally Posted by 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

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

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Originally Posted by AMSS

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

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

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Originally Posted by Mirek

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

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Yes so I heard as well

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.