|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.
Click here to read