Forcing air into the intake, unless very turbulent, cannot be a hinderence to performance.
Air entering the intake because the engine is pulling it out the other end is a normal function. Adding air to to the intake by force without the expense of using additional energy can only be a plus.

Logic therefore dictates that ram air is likely a positive force in the performance of the engine. The question remains, how much.

My experiments did not measure air compression of any significance. However they did measure higher static manifold pressure despite changes in the exhaust orfices used on the ram tube.

A closed 4.0" ram tube held 6 inches at 60MPH.
It read the same whether we had a 1/4" exhaust orfice or a 2.0"orfice suggesting some compression occured. At 4 .0" exhaust the presure dropped to 0 but was not measurably negative.

If, the intake opening allows enough air to enter to exceed the exiting orfice consumption( or bleed) then the manifold pressure should stay positive. This suggests more available air to the engine provided by the vehicle movement than just by the intake stroke of the cylinder. In other words, the piston does not have a negative force, or as much negative force, as a result of drawing it's air.
Further, since the manifold pressure is maintained higher, there is more oxygen available for the burn.


As you have noted, unless done in a wind tunnel, the dyno could not measure a performance gain. But simple logic suggest one must exist.

I would agree with your conclusions that the forced air intakes in the front would be superior unless tempeature factors are involved.

roadster with a stick