For most race cars, tunnels and sideskirts are either forbidden or highly regulated. So ride height and rake become the only way to adjust the airflow under the car, unless they are regulated too.

All else being equal, more rake will mean more downforce, within limits affected by separation and the air that sneaks in from the side. (Note, there is a huge difference between "separated" flow and "turbulent" flow.) The less air that sneaks under the front bumper, the less lift (ie. more downforce). This is one reason why most race cars run as close to the ground as the rules and/or the suspension travel allows.

From an aerodynamics terminology perspective, the entire car is in "ground effect". That is, the aerodynamics of the car are affected by the proximity of the ground plane. Airplanes are considered to be in ground effect whenever their height above the ground is within a couple of wingspans. Using that as a guideline, you can see that any car is in ground effect.

Do I think that rake has an aero effect on an S2000 with a stock underbelly? Yes. Do I think the magnitude of the effect is significant given the rest of the aerodynamics? No. But I don't have any data on it either way.

 

This means you would have to juggle in between setting roll center and aero simultaneously.

 

Yeah, and your point is?

In setting up a car, you have to juggle many things simultaneously.

 

The tunnels and sideskirts are engineered by aerodynamics experts from the beginning to provide maximum benefit within the rules to be run at a pre-determined or standard base line ride height and rake. When you adjust rake, not only would you be affecting aero, but roll center as well. If the roll center was adjusted perfectly, re-adjusting rake to increase downforce may not be the best avenue. Keep in mind, you can also adjust the wings to provide more downforce. Also, there are mechanical methods of obtaining grip or affecting balance as well.

 

Ok, I see your point now.

BTW, that's why I said "the only way to adjust the airflow under the car", not "the only way to affect the aerodynamics".

 

I have heard many times throughout the years the debate of "Downforce vs Drag". I worked with a Toyota Atlantic team for a season. I have worked with engineers and a crew chief. I never once heard anyone discuss weighing the differences of roll center vs ground effects



Mike

 

I would not trade more forward rake for more aero effect under the car for the benefit I think I feel on turns. I made sure I had a better than nothing factory 'splitter' up front, and a rear wing for Cal Speedway, as these will have a greater effect than rake, imo, to a degree. I also certainly don't want to go with the S2000 nose up, though with the rear wing and some acceleration, I might get a little. See some in this picture?

 

Looking good