[svxfreq]

Yes, the wave travels to the back of the pipe and back again at the speed of sound, about 250ft/sec. When it first travels away from the valve it is a positive pressure wave, when it enters the collector it reverses and part of it returns as a negative wave, now IDEALLY in a perfect world you could tune a car for a certan RPM so that the wave not only returns to the valve right before it is closing, creating negative pressure outside the exhaust valve, sucking whatever exhaust out, but you could also tune it in such a way that another negative wave will return to the exhaust valve just as it is opening, creating a negative pressure outside the exhaust valve again, making it easier for the chamber to expell the gases.

All headers will do this, but for example, equal length headers will do this at some specific RPM, this RPM will be decided by the length and diameter of the primary header pipe.

The problem with this is that you can have the negative effect happen at a certain RPM, where the wave travels back and forth twice and returns to the valve as a positive pressure just before closing, this is what makes exhaust tuning extremely difficult, to tune this properly to the ideal conditions I would need an all wheel drive dyno of course, which I just do not have access to, which is why I am doing all the theoretical calculations possible to get an answer that is hopefully close enough to make some extra power out of that engine.