ORIGINAL: ericheller
ORIGINAL: Frost_
shorter=more torque in the middle, longer = more top end HP., It is like a real car in this aspect, to make torque you want some back pressure, but at hi-rpm's you need much less to ensure full exhausting of gasses because remember your engine is a pump, more RPM's need more air in and more out.
the length of the pipe has nothing to do with backpressure. its the pressure wave and the length of the pipe is what controls this. a shorter pipe has a higher powerband, and a longer pipe has a lower powerband.
Believe whatever you like.