Originally Posted by Fabrik8

You're not getting what I'm saying. I've already said that this will work well if the hood/windshield area is designed to not have an area of local flow separation and high pressure. I just consulted a few of my racecar aerodynamics books, and verified that some of the prototype racecars use this method because they have a flat underbody. The cockpit glass is shaped like a bubble, and the flow from bodywork (there isn't really a hood obviously) to windshield is very carefully matched, with a slight upsweep on the edge of the bodywork where the cooling flow leaves and flows over the cockpit. Elsewhere in the book it mentioned how bad this was for passenger cars because of the inverted flow area at the change in angle between bonnet and windscreen (I love British books). They had some SAE cooling outlet recommendations for passenger cars, none of which included anything at the base of the windshield. The non-normal ones that I noted were the hood vent type, which is what most racecars use, and the inlet type, like the top mount intercooler on most turbo Subarus.. They noted that the flow MUST exit into a low pressure area (which is NOT the base of the windshield because of the inverted flow) and that the engine compartment doesn't have much pressure in it because most of the pressure is dissipated when going through the radiator. The best cooling flow exit is out of the bottom of the engine bay and the wheelwells, both of which are low pressure areas. It seems that given the pressure under the car, and the pressure at the base of the windshield, air will probably enter at the back edge of the hood, and exit under the car, which would help in cooling if the pressure difference was big enough. Also, at low speeds everything changes because of different boundary conditions related to air velocity and flow attachment.

So at the recommendation of some very highly regarded experts, I'm going stick to my previous statements. If the whole area at the back of the hood, including the windshield, is designed to have cooling flow exit there, it should work great..