I know that with the Bernoulli Principle, a high velocity fluid causes an area of low pressure. A wing shape gives lift because the air is moving around the wing faster on the top due to the curve (the air has to travel farther) than the bottom so the top has higher velocity fluid and lower pressure.The vent theoretically pressurizes the fender at speed (not shown on a dyno).
I considered this when I did my homebrew CAI. I don't have any measurements to back this up, however I feel that any pressure generated by the bumper inlet will be lost to the engine compartment. (Keep in mind the engine compartment is also vented to the underside of the car.) I put a plastic baffle between the intake area and the engine compartment, but that will not allow the inlet to pressurize much.With the bumper inlet, I don't think it pressurizes the air inside the fender and the engine compartment any more. There would be an area of low pressure just outside the fender also relative to inside pressure as it is a high velocity fluid going around the car.... It does bring cooler air though, which is more dense.
Any other engineers have an idea here? BrickPig?