Erm. What I meant to ask was; I'm getting ready to create the flat bottom undertray for the engine bay and the rest of the bottom of the car. Car will be completely flat except for a cutout where the oilpan sticks down about 2cm. There will also be vents, but that's not my question.
Specifically I'm wondering about diffuser shapes at the rear. I don't have any experience with diffusers, how long do they have to be? What's the best shape for a rear diffuser? How far under the car should it start? How wide? I don't know anything 'bout the subject.
Can anyone provide links to someplace that will give me information?
Thanks
Graber