@jffr posted:Those roof spoilers are designed to smooth the air flow over the top of the car. When Hall Pantera was selling those roof spoilers it was said that it created downforce? Hall copied it from some Ferrari model from the early 1980's. If you want to see how much air that spoiler is actually directing into your engine bay, just put some yarn on it and drive the car. I bet you will see that the air from under the car will push the yarn back to the rear of the car. This test with yarn isn't as dramatic as putting the car in a wind tunnel, but the results are the same. If you are using a carburetor, how are you measuring the inlet air temperature? I am sure that some type of temperature monitor could be installed in the intake manifold or the air cleaner base. In order to prove that any device is actually working, there needs to be some type of before and after testing.
I completely agree.
I've also seen drawings where the air from the roof was supposed to pass under the roof spoiler and thus reduce the negative pressure above the rear hood........