Whenever radiators, cooling, and airflow are discussed here on ecomodder, it seems someone always brings up the merideth effect 'like they did with the P-51 Mustang.'
Here's an idea I had. Dunno if it would work.
Create a 'combustion' or expansion chamber under the car and duct all exhaust and radiator heat into it. The venturi between the rear wheels accelerates the air and you get thrust off the bottom of the rear bumper. Yeah, right.