I see time and time again when the subject of tuned pipes for stunt use rears up - the mention of divergent cones convergent cones, stingers and all the things one would expect to find on a full size power pipe.

  Now this puzzles me somewhat as all I have ever seen when looking at a full length 'stunt' is a header, followed by a megaphone section with its divergent cone, a parallel walled section for volume and some kind of flat disk reflector that effectively terminates the tuned area. And no real convergent cone anywhere.

  Many pipes look like they have a convergent cone but they really are just a length packed with sound reflecting disks with the tune no more effective than that of a of a gun silencer, dissipate everything and converge nothing.

  To me a 'stunt' pipe purely extracts the spent exhaust gases better than an open face system courtesy of the negative pressure wave caused by gas expansion and as a consequence increases fuel consumption. And there is no real focused positive wave packing the waste charge back into the combustion chamber.

  So, having said all of that (and most likely some of it is in error) does a 'stunt' pipe simply go on and off tune purely by the use or non-use of its negative waves?

Thanks.

Thanks for the quick reply Randy, so your pipes do have a positive wave charging effect?

The Brian Ether pipes do follow the formula I outlined though, at least that is my understanding of it the last time I spoke to him.