Quote:
Originally Posted by aerohead
Actually the drag is caused by the air going through the cooling system and the tortuous path through the engine bay on its way out.
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The only drag that matters is the resistance the air encounters going in. It doesn't matter what the path is inside, except the effect on the resistance to inflow. A grill block has 100% resistance to inflow, but if it's angled the flow over the top of it will be much easier.
Do a thought experiment-- picture a powerful fan pulling air through the engine bay. Of course it's not going to increase drag, regardless of how much turbulence and resistance there is inside. All that matters is the force exerted on the airflow outside the car.
The difference between a rear block and the engine bay's aerodynamics are that one pushes 100% of the air back out, and the other pushes some fraction back out.