Rally1 Aero Development

[Sulland]

A lot of very good info in the old aero thread, so we deserve a new one for the new breed top car!

What are the main differences in the Rally1 regulations vs WRCar when it comes to aero?
Will we see lower cornering speed due to simplyfied aero?

[Sulland]

I borrow the link to this thread as well.

https://www.wrcwings.tech/2021/11/12/rear-aero-modifications-in-the-2022-toyota-gr-yaris-rally1/ (https://www.wrcwings.tech/2021/11/12/rear-aero-modifications-in-the-2022-toyota-gr-yaris-rally1/)

[lluisva555]

Officially, the new regulations forbid

- the use of internal ducts (those intakes/vents used for cooling purposes) to get aero benefits
– simplified aero part at the car rear (while maintaining the rear wing): removal of the rear diffuser, and rear fender vents
– free volume area maintained, to keep the aggressive aesthetic of the cars: that is, to allow the use of aero parts in the lower half of the car (front splitter, skirts)

However, the images from the mule test cars do not show any dive plane, front winglets (on top of front fenders) and fender vents, which matches with the original idea of reducing costs (as these are easy to lose parts). We will see how the final designs are, but I think the Puma gives enough clues about what is allowed and what not.

About cornering speed, on gravel there does not seem to be a big difference, but there aero is less important, while mass transfer possibly plays a bigger role (due to the 100kg extra at the rear). On tarmac and fast gravel roads is where we will be able to quantify the impact of the trimmed aero.

[Sulland]

It looks like suspension travel is less on Rally1 than on Wrc17.

If correct, will that in any way influence aero somewhere?

[lluisva555]

It looks like suspension travel is less on Rally1 than on Wrc17.

If correct, will that in any way influence aero somewhere?

Absolutely yes. Less suspension travel means that the car remains closer to the ground, which means less space for air to enter under the car, less pressure and less lift, that is, more downforce.

But there is also car stability: you need the car to be stable, not bouncing. The more stable, the more effective are those aero parts working under the car (front splitter, dive planes, side skirts, rear and wheel diffusers) Ideally, with less suspension travel, the car will bounce less... but someone with good suspension knowledge may probably refute that.

[dimviii]

Ideally, with less suspension travel, the car will bounce less... but someone with good suspension knowledge may probably refute that.

quite the opposite.

[Mirek]

Absolutely yes. Less suspension travel means that the car remains closer to the ground, which means less space for air to enter under the car, less pressure and less lift, that is, more downforce.

That's a misconception. More suspension travel does not mean greater ride height. It means that the car is able to keep wheels on the ground for higher percentage of time in stage (on crests, in deep cuts etc.) and thus make the traction and handling in such situation more efficient but it doesn't mean that the car sits higher above the ground. Absolutely not.


But there is also car stability: you need the car to be stable, not bouncing. The more stable, the more effective are those aero parts working under the car (front splitter, dive planes, side skirts, rear and wheel diffusers) Ideally, with less suspension travel, the car will bounce less... but someone with good suspension knowledge may probably refute that.

As Dimitris wrote - it's exactly the opposite. The car bounces more with less suspension travel because the dampers need to cope with the same bumps on shorter travel distance. Large suspension travel allows smoother ride.

Please check this. That's a great example of what the suspension travel does. The first is an S2000 car with very long suspension travel (for asphalt setup), the second is a gr.N car with extremely short suspension travel given by the stock configuration (especially on the rear axle where the damper length is limited by the usable boot space). https://youtu.be/4pMXwtRx_yk?t=206


I don't know if one can say that less or more suspension travel has that dramatic impact on the function of the aero features but I dare to say that the opposite way is certainly true. The more effective aerodynamics the higher is the downforce which rises with the square of speed. That means the suspenion must be able to cope with huge differences in the vertical load from one corner to another. That is IMHO extremely challenging and we could see plenty of times teams struggling with that even in the fourth year of the WRC 17" era.

[ictus]

Absolutely yes. Less suspension travel means that the car remains closer to the ground, which means less space for air to enter under the car, less pressure and less lift, that is, more downforce
ride height and suspension travel are somewhat related but it doesn't mean that tha car that is higher has to have more travel

[lluisva555]

Got it! Thank you all, I was confused on that. Great to learn!

[becher]

I think the shorter travel is aerodynamically not a benefit for a rally car, after all you want a "stable" aero platform, with less suspension travel the cars are likely not "floating" over any terrain any more and the airflow will be disturbed even more than it is now on a WRCar. If that even has any effect on the very simple looking aero of Rally1 cars is a different story, although i doubt it will be significant.