Bevan sounds like your referring to the "cowl induction" effect. The air piles up at the base of the windshield and "feeds" the engine scoop more effectively than if the scoop was facing forward.
BUT, the windshield on this Bill E. example car is VERY laid back. I can see where the windshield may in fact have a "wing" effect.
I to would test this application using the "string theory", there may be more than "three dimensions" to this thing (pun intended).
Ernie