Technical Analysis: WRC Cars 2017

[Mrpengski]

Revman, teams were allowed a certain number of "jokers" to spend on updating homologated parts (it's not free-for-all like F1 for example), split between engine and chassis. How they count each update is a bit open to debate, so one joker could be a single new hole on the OEM chassis or 1 bodywork and all other panels that connect to it... So for you it would be a bit of work (but fun) trying to figure out who used the jokers on what without looking at the homologation dossier. It's a "use it or lose it" situation so one can assume every team used their full allowance (or maybe not??). For 2018 there are less jokers available, so they must be more selective about what is worth upgrading this way. Then there are parts which are homologated but multiple options are allows and can be added through the year (every 3 months) without restriction. The distinction between the two types of homologation would not be obvious without reading the technical regulation, unfortunately.

So what it all means is, some cars may look obviously different externally, while some may not, but you bet all of them would have had upgrades throughout 2017 and between the seasons for parts where jokers were not needed. I think most cars had one or two clear deficiencies, which would have been the focus of upgrades. We will now wait for Monte Carlo 2018 to see how well they improved them.

[sonnybobiche]

Are wiring harnesses/ECU box/electric gubbins homologated?

[Mrpengski]

Are wiring harnesses/ECU box/electric gubbins homologated?

Mostly, yes.

[Revman]

Thank you for this reply. Tremendous. Do you see any trends regarding the aero (given that this is what we can see)? I read on one site that Toyota may have narrowed the front bodywork, revised the "grill" area, and added an upper dive plane to offset the massive wing. All speculation, or do you think this is a legit analysis?

[Mirek]

I have one question...

Does anyone remember whether they kept using cross-tyre setups with 2017 cars? I am asking because unlike the old generation cars the new ones have active center differential.

[Watson]

Does anyone know why in the WRC they use only one shift pedal where you pull to change gears up and push to change gear down instead of the two pedals they use in other series?

[mArvAlcao17]

Does anyone know why in the WRC they use only one shift pedal where you pull to change gears up and push to change gear down instead of the two pedals they use in other series?

I guess the purpose is to keep left hand handle the steering wheel while the right hands are all about shifting & handbraking.

Mitsubishi experiment double paddles in 2005 though

[Watson]

I guess the purpose is to keep left hand handle the steering wheel while the right hands are all about shifting & handbraking.

Mitsubishi experiment double paddles in 2005 though

Oh I see. Rallycars probably have more turning lock and therefore more turns from lock to lock so the shiftpedal on the left might be clumsy to reach in certain situations.

[Mirek]

Usual lock-to-lock rotation in WRC cars is 1,5 if I am not mistaken.

[AMSS]

I have one question...

Does anyone remember whether they kept using cross-tyre setups with 2017 cars? I am asking because unlike the old generation cars the new ones have active center differential.

I can`t remember which rally it was but at least Latvala used cross setting as he complained about the behavior when they hadn`t used it i testing and the car felt nervous on the rally, also based on the Michelin reports of what tires each crew had they would almost have been forced to use cross settings.

[AnttiL]

I'm also interested in the cross tyre setup. What are the pros and cons? I understand the drivers have a limited amount of tyres per rally so sometimes that's what they have to do. But how much does the diff balance it out?

[Revman]

I'm also interested in the cross tyre setup. What are the pros and cons? I understand the drivers have a limited amount of tyres per rally so sometimes that's what they have to do. But how much does the diff balance it out?

Yes, and what is the thinking? For example, a softer tire goes to which wheel on a four wheel drive race car under what circumstances (surfaces)?

[Mirek]

I'm also interested in the cross tyre setup. What are the pros and cons? I understand the drivers have a limited amount of tyres per rally so sometimes that's what they have to do. But how much does the diff balance it out?

If I remember right it was Juho Hänninen in 2011 Monte Carlo who used it first (or at least it was first widely discussed case) when Škoda team (and Petter Solberg) fucked-up tyre choice and lost the fight for victory there. He used it out of necessity and it worked much better than let's say two winter tyres in front and two slicks in the rear.

I believe the main rationale lies in the fact that limitted-slip differential helps to bring overall grip level of the axle closer to the level of the better wheel. In that case an axle with only two wrong tyres benefits in no way from having LSD in between. Therefore if You have two better tyres it's better to place one in front and one in the rear (cross) and by that enhance a bit the grip on both axles instead of having one good and one useless.

[denkimi]

its just that 2 good wheels on the front give to much oversteer, and 2 good wheels on the back too much understeer. so they use on wrong wheel and 1 good wheel on each axle, which gives a more stable feeling.
the only reason they do that is because they can't carry for spares in the boot.

[dimviii]

some close photos from yaris and new canards and front wing from https://twitter.com/Traxx_WiF/media

https://pbs.twimg.com/media/DSs9QKfX0AAJBTW.jpg
https://pbs.twimg.com/media/DSs9QKoXUAA8QPR.jpg
https://pbs.twimg.com/media/DSs9QKqXUAAkRQ3.jpg

[pantealex]

Those are still prototype parts, just saying ;)

[RS]

When do the current WRCar regulations run until?

[Mrpengski]

Thank you for this reply. Tremendous. Do you see any trends regarding the aero (given that this is what we can see)? I read on one site that Toyota may have narrowed the front bodywork, revised the "grill" area, and added an upper dive plane to offset the massive wing. All speculation, or do you think this is a legit analysis?

Agree on all points. Now that more detailed pictures are showing up online, it's even clearer what they did. I particularly like the outlets towards the side of the car on their new front bumper. Pre-2017 cars all had this type of openings on the side, which help manage the air around front wheels. For 2017, the tech reg didn't appear to allow this treatment at first... But clearly with some clever thinking, it's still possible. Good for them! There are other details which are probably very difficult to photograph. Maybe they got some help from the aero department in Cologne? :D

[Mrpengski]

If I remember right it was Juho Hänninen in 2011 Monte Carlo who used it first (or at least it was first widely discussed case) when Škoda team (and Petter Solberg) fucked-up tyre choice and lost the fight for victory there. He used it out of necessity and it worked much better than let's say two winter tyres in front and two slicks in the rear.

I believe the main rationale lies in the fact that limitted-slip differential helps to bring overall grip level of the axle closer to the level of the better wheel. In that case an axle with only two wrong tyres benefits in no way from having LSD in between. Therefore if You have two better tyres it's better to place one in front and one in the rear (cross) and by that enhance a bit the grip on both axles instead of having one good and one useless.

Interesting. The cross tyre setup was a new concept for me when I joined WRC. I do recall the WRC TV commentators were discussing the merits of left-to-right mix, instead of cross. Apparently this could give them more confidence because the car will behave more predictably, albeit at different grip levels left and right.

[Tarmop]

When do the current WRCar regulations run until?

"The principles of the technical and homologation regulations for the 2017-2019 WRC car were approved by the World Motor Sport Council."