Technical Analysis: WRC Cars 2016

[itix]

There is nothing wrong with the machinery. Maybe they could do with a bit more power and nothing changed in the rest of the car but I doubt that you could make the cars more spectacular with any other comprehensive rules change.

The inwards caster angle (which is not called inwards caster angle but I have forgotten what it is actually called) seem to be virtually nil (or 90 degrees or however you put it) on all the current WRC machinery, am I right?

So in my mind the main reason for VW dominance must be "a bit of everything". From onboards they seem to have a much better engine as from any given moment where cars exit the corner or take off from the start line they always seem to arrive at the next corner faster to what you compare them with.

At the same time, you lot say that it looks more easy to drive. I don't actually understand a shit of this so can't really judge. I understand this with low centre of gravity and the importance of the contact with the road surface and all of that but I just don't have the know how to translate it to technical details. I've come to understand that the dampers these days are basically oil filled with ball bearing type support for taking up horizontal forces to minimise friction but i am sure that all the big companies do this today. The reservoir, is it some form of small gas accumulator in there which you can alter? I very much doubt that all of it is oil with the suspension travel they have. It is impossible to compress oil that much.

One thing I can tell is that the manufacturers manage boost control very differently. Hyundai still has a relatively pronounced chirp on shut throttle body... I think it is VW that also has a pretty distinct chirp as well (but different in sound). They all have exactly the same bore and stroke according to themselves (83 and 73.8 mm) so the difference, which is audible, must come from things like boost management, difference in the ALS systems and other electronic engine controls as well as minimising mechanical and thermal losses. I am pretty sure that the airflow to the engines is as optimised behind the restrictor as it can get so most effort is probably in maintaining boost pressure as close to the FIA 2.5 bar mandated number as possible at all times.

If I remember the rules correctly you are locked to one set of gear and differential ratios for the entire season so I am fairly sure this is close to optimised as well.

This leaves us with things like the body stiffness, difference in dampers and spring rates, geometry and length of wishbones, weight of components and how low you can ballast the car, neutrality in turn in and weight transfer and predictability for the driver I guess. A car that's easy to drive would also give you confidence to push everywhere.

[janvanvurpa]

I have to be honest - because of the regs, I find the current WRCars probably the least interesting of current world motorsport machines.

I dunno..I find the complete and utter lack of good detailed information diminishes my interest.
I wish I could get nice line drawings, clear unobstructed photos of the suspension showing the suspension geometry and angles just to ponder...
I know this is motorsport and the first part of the word is MOTOR and most "fans" and even most lower level participants seem to fixate on motor....and there's been some really good and meaty discussion right here over the years on the motors, but the real decisive difference between our collectively beloved rally cars and other types of cars is mainly been in suspension (and to some degree in diff design--and function), especially if you look at rally cars over a period of time...
This idea has some merit if we recall not so many years ago when Juha Kankunen made a guest starring role in WRC Finland YEARS and YEARS after he was last in serious competition and he was asked what he thought of the car..He seemed his normal casual self when asked about motor and power "Oh we had plenty power back then" but when he got to suspension and brakes, his eyes lit up...there was what evidently was for him the big revelation.

But instead of good clear photos of parts and pieces and parts installed.....and being able to see and wonder about this huge advances instead....


people want to discuss in detail paint schemes.

mon dieu ma pauvre sport

[janvanvurpa]

Maybe the technology. If I recall some of the suspension points on my second generation Impreza are based on experience with the WRC.

No not really..Look at the entire rear of the car....The upright or knuckle, subframe, mounting, is totally different design with the strut being entirely forward of the hub on your car while all the Group a and Whirled Rally cars had normal conventional upright with the strut fixed directly above the hub..
The old Group A rules under which first Le-gassy and GC8 were homologated mandated that suspension mounting points had to be within +or - I think 15mm, maybe 20mm.
This locked in design to some degree, but nothing was the same in any way.. Have you seen the site selling all kinds of Surau WRC spares?..Fascinating seeing the hege variety of parts there

WRC rear upright and hub:


OEM


One of these is not like the udder.

[TWRC]

There is nothing wrong with the machinery. Maybe they could do with a bit more power and nothing changed in the rest of the car but I doubt that you could make the cars more spectacular with any other comprehensive rules change.

The inwards caster angle (which is not called inwards caster angle but I have forgotten what it is actually called) seem to be virtually nil (or 90 degrees or however you put it) on all the current WRC machinery, am I right?

So in my mind the main reason for VW dominance must be "a bit of everything". From onboards they seem to have a much better engine as from any given moment where cars exit the corner or take off from the start line they always seem to arrive at the next corner faster to what you compare them with.

At the same time, you lot say that it looks more easy to drive. I don't actually understand a shit of this so can't really judge. I understand this with low centre of gravity and the importance of the contact with the road surface and all of that but I just don't have the know how to translate it to technical details. I've come to understand that the dampers these days are basically oil filled with ball bearing type support for taking up horizontal forces to minimise friction but i am sure that all the big companies do this today. The reservoir, is it some form of small gas accumulator in there which you can alter? I very much doubt that all of it is oil with the suspension travel they have. It is impossible to compress oil that much.

One thing I can tell is that the manufacturers manage boost control very differently. Hyundai still has a relatively pronounced chirp on shut throttle body... I think it is VW that also has a pretty distinct chirp as well (but different in sound). They all have exactly the same bore and stroke according to themselves (83 and 73.8 mm) so the difference, which is audible, must come from things like boost management, difference in the ALS systems and other electronic engine controls as well as minimising mechanical and thermal losses. I am pretty sure that the airflow to the engines is as optimised behind the restrictor as it can get so most effort is probably in maintaining boost pressure as close to the FIA 2.5 bar mandated number as possible at all times.

If I remember the rules correctly you are locked to one set of gear and differential ratios for the entire season so I am fairly sure this is close to optimised as well.

This leaves us with things like the body stiffness, difference in dampers and spring rates, geometry and length of wishbones, weight of components and how low you can ballast the car, neutrality in turn in and weight transfer and predictability for the driver I guess. A car that's easy to drive would also give you confidence to push everywhere.

Found this on another forum, it explains the external reservoir dampers better than I could:

"The interior of a shock is a closed system, but as the shaft goes in and out of the damper body, the available volume in the system changes because the shaft takes up some space.

Since the oil is incompressible, you have to have some gas in there to account for this change in volume. Separating the gas from the oil with a sliding piston keeps the oil from frothing up. But it also makes the shock body very long unless you 'remote' the part that has the piston in it. That's the whole purpose of the reservoir. The amount of oil that flows into the reservoir as the shock compresses is the exact volume of the shock shaft that has entered the damper body."

Here's a good site on the DS3's suspension geometry; the reservoir is the big tube hanging off the top of the damper, or in a Reiger rally damper's case, it's the purple tube attached to the bottom of the damper body. Hope this helps.

[Gregor-y]

WRC rear upright and hub:


OEM


One of these is not like the udder.

Did the homologation rule for mounting still hold sway in 2001? It's definitely a different location unless the struts are massively misshapen. Now that the rust's fixed I'm waiting to see if the next failure will be the wheel bearings which is why I'm a little familiar with these parts. All the yahoos want to use ceramic this and polyurethane that which can't be comfortable or long-lived.

[Tomvwb]

Mirek, Don't think about the helper spring to much, its never used while normal driving only used when there are jumps. But the difference between the sachs en the reiger is that the reiger has developed a pure mechanical hydraulic system RCV. this system feels when the wheel is not touching the road and releases the rebound so that the wheel is making faster ground contact. thats why there is a lager helper spring, to push the unsprung weight as fast as possible out, even until the last mm.

About this topic, there are a lot of suspension designs, made for a lot of reasons, travel, brake cooling, forces, but most important how the geometry changes while body roll or travel changes. because this is the actual wheel grip together with the load on that wheel.

About the new I20 WRC, there are some complains about understeer, but remember who tested the car , Abbring is always driving very much understeer and also searching a set-up for this. witch results in fast corner speed and early on throttle with great traction on rear. but he has already proven that's a fast way of driving (check again Kevin's palmares, the only vw test driver that could match the speed of Ogier in 2012, not consistent but on some stages.). other drivers will adapt this driving style or change the setup slightly.

[Toyoda]

This thread is brilliant,
It actually reminds me of another annoying thing that WRC doesn't do but F1 does.
F1 frequently have articles about various aspects of the F1 cars and the differences between them, often semi detailed schematics and the pros and cons of the different designs, engine, aero components, suspension etc
Would be sweet if the WRC official journalists got off the ass and did some real analytical stuff! Instead of the fan boy and regurgitated crap articles they do at the moment.

Interesting that Hyundai continued down the French route, even though Neuville did his best season with MSport and Paddon's style I imagine also would not suit it? Surely
copying and improving on the most successful car (VW) would be a logical method for the development of Hyundai's new car? Or is it an experience (engineer/design personal) /safe (previous data from old i20) option thing?

[AndyRAC]

It's not just F1, the WEC has loads of details about the different technical aspects of the cars. As you say, WRC journalism isnt great, in fact it's so poor it's not funny. We mostly get PR pieces rather than serious journalism.

[Mirek]

Mirek, Don't think about the helper spring to much, its never used while normal driving only used when there are jumps. But the difference between the sachs en the reiger is that the reiger has developed a pure mechanical hydraulic system RCV. this system feels when the wheel is not touching the road and releases the rebound so that the wheel is making faster ground contact. thats why there is a lager helper spring, to push the unsprung weight as fast as possible out, even until the last mm.

Thanks, I know about the Reiger rebound control but I didn't realize that the helper spring is actually a part of it. Now it makes sense to have stronger ones. It brings a small disadvantage of added unsprung weight. Can't say how much is the difference but the helpers on Fiesta are a lot more massive than on Fabia. I guess it's not so significant but it's another difference to full picture.

Interesting that Hyundai continued down the French route, even though Neuville did his best season with MSport and Paddon's style I imagine also would not suit it? Surely
copying and improving on the most successful car (VW) would be a logical method for the development of Hyundai's new car? Or is it an experience (engineer/design personal) /safe (previous data from old i20) option thing?

I would say that it's about personal experience. I believe the i20 was designed mainly by former Peugeot/Citroën guys.

[Karukera]

So partly is the Polo.
Besides Skoda's technical legacy, FX Demaison is a PSA shaped engineer, Sainz last WRC drives and development at Citroën took an early grip on the Polo and Ogier came from the successful DS3.