I think Ste meant because of the price of them. Thats my standpoint on them at least. And stick with it, as its already on the car when i collect it.
Ive not looked into them much, other than new they are close to a grand. For an induction kit. Id buy a Kpro over that all day long.
Ive yet to find one thread showing proven gains over any other filter. Not saying they dont give gains, just all i see if GruppeM is the best.
Ive never been sold on any kind of ram effect design. Im no expert, but ive done enough training courses, with enough manufactures to have a decent understanding. So im not claiming i know better than GruppeM, Js, or anyone else. I get the more air faster idea.
Inlet manifolds work around pressure, and vacuum. An engine is essentially pumping air, with some fuel thrown in.
Atmospheric pressure, the air all around us, is 14.7 psi at sea level.
If you were to read your MAP sensor, with the engine not running, it should read around 1 bar. 14.7 psi.
A typical inlet pressure reading would be around 300 millibar at idle (4.35 psi)
An inlet manifold pressure during WOT would be around 1 bar, 14.7 psi, atmospheric pressure.
As a piston lowers, it creates a low pressure area, the pressure differential allows the void to be filled by the atmospheric pressure air outside the inlet manifold.
Without getting too in depth, and confusing myself even! A tropical storm, so were talking winds of 39 to 73 mph. Probably a good example of typical road speeds we see regularly. Air pressure in a tropical storm system is around 990 to 1010 millibars, or 14.36 to 14.65 psi.
So not much change from air at 0 mph, to air at 73 mph. So i really do wonder how ram air effect plays a part.
It starts getting into complex equations, laws of temperate to pressure and so on.
I dont know how to calculate to volume differential between 73 mph air pressure, and 0 mph air pressure. I certainly dont know how to factor in IAT.
I would say, that restriction of flow (better design and filter media) is probably where most gains come from.
Matching of inlet tract, throttle body, and plenum size is also an area gains can be made.
So i would expect kits to have improvement here.
Anyway, ive finished rambling now! Point me to a dyno comparrison someone. Ive yet to find one.