The 2-Stroke Expansion Chamber

There are a lot of misconceptions and misunderstandings about 2 stroke exhausts.
First and foremost is that expansion chambers are not expansion chambers are not expansion chambers!!!
Meaning that different pipes may have WAY different results due to the way they are designed.
Below I have written a quick overview of the 2-stroke pipe.

A 2-stroke expansion chamber (which is what performance exhausts are vs. the touring exhausts which are basically just exhausts for noise reduction), is kind of a black art in its design... With slight alterations, it changes your power band curve... At what RPM the power band is made, how much HP is made in all different RPM ranges inside this curve...

The length of pipe from exhaust port to the expansion chamber is one factor... The length and the angle going into the expansion chamber is the next, followed by the length and diameter on the chamber itself, followed by the length and angle of the taper down to the exhaust pipe and finally the length of the "stinger" or the final tail pipe... etc. The photo below shows the entire "Guidelines" for pipe design.

Any modification in any of these factors completely changes the characteristics of how the motor will run. It all has to deal with the cylinders port timing and sound or pressure waves generated by the motor. 2-stroke motors rely on back pressure and draw or vacuum to pull gas through the motor. Changing the characteristics in the pipe changes these resonant waves which is what actually alters the way the motor runs.

But as I said, slight modifications alter the way the motor runs. Which is why different pipes will give you WAY different performance results. So it is a good idea to research particular pipes and get feedback from others that have used them to evaluate which pipe will work the best for your needs.

No sense in re-inventing the wheel, so I dug up a good article if you would like to read into pipe design a bit more.

Go HERE for more detailed information.