Originally Posted by
mrwho
There are no formulas to predict the performance or optimise the performance of the design of a header. This is because the exhaust gases are moving at, or have portions moving at transonic speeds. At these speeds there’s no way of knowing exactly how the exhaust gases are going to behave. The pressures can increase and decrease at the same time inside a pulse moving through a high velocity point. There are just too much dynamic pressures and density events happening inside a proper exhaust system to even try and apply maths formulas to. You can try… but it isn't going to help your header design. They call it a dark art for a reason…
My advice to you or anyone building/designing an exhaust header would be to spend most your time concentrating on the collector. Remember choke is GOOD! Choke = power!
IF you get the collector right, which is very difficult to do even with alot of experience, you can use long primaries to your advantage. Don’t worry about all that equal length primaries nonsense.
By the way, do you know how to weld or fabricate? It would make building the header a lot easier.