Join Date: Apr 2005
Location: SW Washington State
Exhaust back pressure isn't necessarily a condition or size of the exit point of the exhaust but also the volume of the can and the path in which the gases must move. A different path will create different pressure pulses and a smaller volume will build pressure more quickly with a smaller volume of gases, again changing the back pressure and of course the haromonics of the exhaust sound. Which is the point of most doing this, they want a different sound for no cost, IMO not a reasonable trade off . The changing of the pressure pulses can signifcantly affect the scaveging and the cylinder filling ability of the intake system. Almost never will it be for the better on a home "designed" system across the rpm range. Usually a change of this type "may" result in a wee bit more hp on the top but at a significant cost of torque and hp on the bottom end where the bikes are used most often.
"Travel has no longer any charm for me. I have seen all the foreign countries I want to except heaven & hell & I have only a vague curiosity about one of those."