There is a rotation. If I remember correctly, viewed from the rear, the left side rotates counter-clockwise, and the right rotates cloclwise. The cloud forms on the underside of the wing, where it seems the air is moving the fastest. The angle of attack on the wing of a sprint car is relatively...
I suppose it's a contrail, but it's not exactly a trail. I guess it's more like a block of low pressure (sounds like a weather system). I'll see if I can find pictures of the contrails and post them to my site.
I used to race with a club called NSRA (www.nsraracing.com) that runs winged sprint cars on asphalt tracks. Every once in a while, especially on the larger tracks and in colder weather, you'd see little condensation vortices (plural vortex) behind the tips of the wings. Even less often one could...