Originally Posted by elp_jc
You don't need that if you use common sense. IF there's any restriction, it's at the top of the rpm band, when the engine needs the most air. And if you still can't see that, just do a dyno with no air filter. If you don't get your 13HP 'across the board' (you won't
), then how the hell can you get it with a filter in place? That should answer your question, even if you don't understand why
So, this is being a little pedantic and not really applicable to the M3, but I have seen some additional and measureable power gains from running a filter that has a nicely radiused velocity stack before a round intake tube, vs no filter at all.