[pokeybritches]

Originally Posted by AmmarYasirA

That's actually really good info, glad that got cleared up. Thanks for this!



So one more question, is the scavenging effect only useful for low end power? Is it there for a better overall powerband or is there another reason as to why you would want the scavenging effect? (Apart from the ones mentioned in the website)

Scavenging is useful at any rpm or power level. It's a tradeoff though, between scavenging and back pressure. Smaller diameter pipes increase scavenging (torque) at low rpm, but cause more back pressure (torque loss) at high rpm. Large diameter pipes are the opposite.

The myth of back pressure being necessary probably came from some guy thinking bigger was better, so he put a massive fart can on his Honda and noticed a power loss at low rpm. While there was indeed less back pressure, there was also less scavenging, and the power loss was incorrectly blamed on the loss off back pressure.

There is no one size fits all exhaust setup. You choose where you want to maximize efficiency. Stepped headers are a compromise between scavenging and flow, but they are still a compromise.