Aerodynamics of a bug

[Jadewombat]

Would this excessive downforce from ducting the front end and the inverted scoop create more drag? That's one thing I can't afford to add a lot on my car, I don't have a lot of hp. I think I understand the theory of it though, the air passing up through the middle or bottom of the front end passes up and over the hood essentially grabbing the front end pushing it down more. Pretty common now on cars with radiators or external oil coolers:



Another thought about running boards, because the bottom side of VW running boards is curved (like the inside of a fender), doesn't this create a vortex in this space for the air to swirl around in and create more lift of the whole car? Meaning, you want as much of the bottomside of the car as flat as possible like the pan, correct? After looking at this highly modified autocross Elise, it looks this gradual taper along the side they have with the fender edges smoothed to the doors work pretty well if applied to a bug:



Those flaps along the back of the front fenders have got me curious as well. A picture of my car attached. Thinking maybe I could do something similar to this Elise, smooth out the area where the running boards would normally attach to the car (circled in purple) so it's flush with the door lines and some small strips of material to smooth out the transition between the fender corners and the pan (circled in red).

[Humble]

Regarding my front fenders, I kept the wholes large and close to the body to fill the void behind the fender. The fender is curved like the body and is is a high pressure area, both good cause for lift. After venting the front fenders I had to add a little more angle on the rear wing for high speed cornering stability. If I did it again I would (and still might) create a larger vent, same vertical size but a little wider and closer to the body.

For the running boards, I've mentioned somewhere before creating a wedge shape much like the ones on the Jeffery's race bug. Sizing them right takes some work and you can be more aggressive on a track car vs. a street car, but ideally they should be as close to the road as possible. Its common practice to use sheet metal or fiberglass moldings and rivet a rubber curtain to it.

[Mykul]

I AutoX with that Elise! Check out the front splitter, it's plywood!

[Humble]

I believe that elise is a nationals car if I remember correctly. Also, plywood sounds so redneck, call it organic composite, it sounds racier that way

[Jadewombat]

Originally Posted by Humble

I believe that elise is a nationals car if I remember correctly. Also, plywood sounds so redneck, call it organic composite, it sounds racier that way

Speaking of which:

http://www.specialprojectsms.com/info/technical.html

Interesting stuff. Anyone messed with a lower rear splitter on a bug near the trans, etc.? Too far back to notice, too turbelent, doesn't matter/wouldn't work with the bug body shape, good experience?? What are everyone's thoughts on the rear diffuser, like on this Acura: