Rally Cars tech stuff

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Originally Posted by dimviii

understeer can create just suspension,suspension+allignment,front diff settings+suspension,or with a little help from driving style,or some combinations of them.No understeer can t be created from chassis,maybe from a wrong mounted engine(just beside the bumper like subarus) but again there are solutions to avoid it.

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Also weight distribution and how the weight shifts under braking also has a significant role to play in this. And weight distribution is a fundamental property from the chassis, if they got it wrong initially there is no way around it but just to compensate through suspension/diff setup.

Most of the current cars are basically same in their general layout. The difference in weight balance can't be so significant like when we compare for example Impreza and Lancer or even more when we compare Quattro and 205 T16. Chassis are very similar, engines of same kind mounted in same locations, rollacages almost same, bodyshell panels are also made almost same way. What playes a more role is sure the weight shifting from suspension and geometry layout.

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Originally Posted by Mirek

I think that is very hard to answer without being an insider. I'm no expert at all but in my opinion some understeering is natural for all AWD cars without central differential. If You watch closely You can see it present with all current WRC/S2000 cars (I started to notice that when first Peugeot and than Škoda found centre diff useless and stopped using it). You can play with diffs, geometry, weight balance (not much under current rules), suspension etc. but for me it remains a question what works the best with these cars. In the ideal world You prefer neutral handling but look at Loeb, he is much more understeering than most of others and he is mostly faster.

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This is characteristic of all 4 wheel drive cars. The first Quattro which had central diff were understeering alot also. The S1 evolution was improvement by shortening the wheelbase and also taking weight in front and placing it weigth to the back like oil coolers.

The main reason why Quattro was so badly understeering was its heavy longitudinal engine in front of the front axle.

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Originally Posted by makinen_fan

Also weight distribution and how the weight shifts under braking also has a significant role to play in this. And weight distribution is a fundamental property from the chassis, if they got it wrong initially there is no way around it but just to compensate through suspension/diff setup.

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weight distribution yes,thats whu i said from a wrong mounted engine=very front mounted at subarus.
chassis ONLY ,can t have a wrong weight distribution,the wrong weight distribution will be if you mount at wrong places all the rest pieces.

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Originally Posted by Mirek

The main reason why Quattro was so badly understeering was its heavy longitudinal engine in front of the front axle.

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True, anyway non 4wd car can oversteer like rwd car

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Originally Posted by stefanvv

True, anyway non 4wd car can oversteer like rwd car

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to oversteer like a rwd is not correct for a 4wd,but you can have oversteer character very easy in a right designed 4wd car.Evos with some tweeks at electronic center diff,and rear alignement can oversteer quite like rwd.

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Originally Posted by dimviii

weight distribution yes,thats whu i said from a wrong mounted engine=very front mounted at subarus.
chassis ONLY ,can t have a wrong weight distribution,the wrong weight distribution will be if you mount at wrong places all the rest pieces.

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yes that's right in that chassis only cannot have any significant difference. By chassis I interpret it the chassis itself plus body, roll cage engine placing etc.

Mirek you are right that there should not be significant difference in WD, but you never know. From my work experience with F1 cars, the engineers are VERY sensitive about tiny changes in WD, not sure about rally cars though. I believe no where near, I would say that changes in +/- 2% would not make much difference. Do you or anyone know approx values for S2000 cars out of interest?

Wasn't the focus Wrc supposed to be 50/50 distribution? I thought I remember them making a big deal of that.

I am intrigued that the idea of the center differential is worthless. Being from the US and not having wrc/s2000 cars we are most familiar with subarus, and the shops that prepare subarus claim the center differential is the most important. Just wondering why the difference in philosophy?

Maybe a bit off-topic, but: BMW X-drive system starts from rear and moves to front axle when frontwheels are starting to slip. Makes the car always steering without understear. Maybe not comparable to WRC/WRC2, but I like it very much myself on wintery small road nearby my home....