Originally Posted by blight
Agreed... there would be actual math to figure this out. The biggest problem is the varying temperature which will vary the speed of sound. At least in my opinion. There would be too many assumptions i believe.
You can refer to Bells book for the tune exhuast length.
Yes there is plenty of math. More than i am going to try to teach over this format. He really just touches the subject. Its usally not to important on car since you will normally buy pre fabbed headers and normally they are tuned for middle of the road performance. Fyi i have seen that book in pdf on the net.
I understand why your tuning the headers to tweak the exhuast note just dont think the x pipe is the answer your looking for.
If you are sure temp is the answer buy an egt and some pipe and start testing. egt will give you the real temp inside the pipe the outside pipe temp is not the same as the gas temp. If your trying to calc a factor of mach usaly called z factor but not sure if that is the proper term or just var. to get the air speed inside the center of the pipe you willl need the gas temp.