Originally posted by clickwir
Somewhat yes. You need backpressure, the larger the pipe the less backpressure there is.
Bad example... ever hear the joke about Saddam H and how he likes to have fun with sheep... well it mentions that he likes to take the sheep near a cliff and then start having fun... point of that is to have the sheep pushing backwards away from the cliff... think of it as backpressure. Without the backpressure, it's not much fun... if there's too much... it's not fun either... finding that happy medium is his goal with the sheep. Ok that was kinda sick... but it shows the point... sorta ... kinda. uh... I have to go now. k thanks bye
back pressure is bad.
it's called flow velocity. piping that's too large decreases flow velocity of the exhaust gases.
you have to evacuate the exhaust as fast as possible out the tailpipe to prevent reversion. too large will reduce exhaust gas pressure, unable to maintain flow velocity. too small will become an obstruction, resulting in back pressure.
back pressure and flow velocity are two different things... properly tuned piping will keep exhaust velocities at it's highest speed to evacuate the exhaust and prevent reversion.