Wheel well skirt or wheel well spoiler?
 

Do wheel wells need to be completely skirted in or would a leading edge spoiler direct air flow across the openings and reduce turbulence?

It seems to me that a leading edge curved-outward deflecting spoiler could push direct airflow out far enough to miss the scoop effect of the rear edge of the wheel well. (Just as front air dams reduce turbulence below the engine compartment.) Then one could tinker with the turbulence within the well itself with an underbody spoiler.

wheel wells
 

Hucho gets into this in his book.I didn't bring mine to town so I'm worthless to you today.I would posit that since all the really low-drag concept cars utilize fully-enclosed ( double -enclosed with the Probe-IV ) wheels,then, that's where the real reductions are found.---------------- A "fixed",and even a 4-season movable skirt might pose challenges in the snow-belt and may not prove practical considering snow buildup and free motion of steering.Something to consider.

Ford GT40 Aero
 

I have the honor of working at a Ford Store where we have a GT40 on display 24hr a day. In fact I can die happy knowing that I have driven it a couple of times.

Anyhow, several salesman and I get into arguments about it all the time and its "awesome aerodynamics", whereas I believe they aren't that great.

So after an exhaustive search on the internet I find out that the cd of the GT40 is .35 ??? WTF, I didn't think it was that bad !!!

However after looking at it closely and seeing how the front tires are directly in the air stream, among other things that are fishy in its design, I guess its justified.

Just thought a couple of you may have wanted to know this ...

0.35
 

If the car was intended for weekend racers,then the drag is probably a concession to handling on the track.I really like the radiator exit duct!

for a supercar designed with lots of downforce to hold it to the ground, .35 is really well designed. remember thats better than most cars and also is pushing down on the car with a lot of aerodynamic force

The last company I worked for did a lot of printing for the automotive industry and they did some poster work for the GT. I scanned through the hi-res images and I think the low stance and cooling duct-work are the only things I liked about it. When I saw one in person parked on a street in Manhattan, I also liked the clear engine cover. That's about it. It's too Lamborghini like for me; too many angles, not enough curves.

Back to the OP, I think if a full skirt is (for whatever reason) infeasible, then a dam might be the way to go. It'd need to be fully tested to make sure that the increased frontal area is counteracted by the reduction in wheel-well drag.