thebru wrote:
I have always been under the impression that getting exhaust out with the least amount of back pressure is best(Ever put Cherry Bombs on a car?). However, the reports I've read on newer systems seem to contradict that. Remember Kirker Pipes? BIG expansion chamber and tiny exhaust tube at the end. The theory was concentrating the exhaust at the end and "popping" it out created suction inside the pipe and actually pulled the next exhaust out.
Exhaust design is quite complicated (and way beyond my limited abilities). It is based on two fundamental principles .... gas particle movement and pressure wave activity.
In general .... straight pipes = good for
WOT .... however, both the diameter and length of pipe will determine the total
HP that you'll get. Large diameter, short pipe = good for high
rev HP.
So if you're going full throttle down the 1/4 mile you want the open pipes design.
If you want to get the best driveability (and fewer tickets
) out of your bike, then you'll need some backpressure and scavenging. The best bang for the bike are the two into one setups as they provide both. Some of the two pipes designs now come with a crossover somewhere along the pipe, which also provides for some scavenging. But they are not as efficient as the large can design.
Either way (can or atmosphere at the end of the header) wWhen the gases come out of a narrow pipe into a larger area, a negative wave is sent back up the exhaust pipe to the cylinder. If timed correctly, the negative wave helps suck in the fresh intake mix into the cylinder. Correctly timing means getting the correct length of header. Now there's the rub.
Doc
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