ORIGINAL: wind junkie
I have a question which also deals with tuned exhaust systems. Unless I misunderstand SPA rules, it =IS= permissible to use the quarter wave tuned exhausts that come with the Jett or Rossi motors in SPA competition, but NOT the 1/2 wave long pipes (and headers) most guys associate the "tuned pipes" which are =NOT= legal, correct?
If that is true, I dont' understand the reasoning, other than one must often tune his header to match a particular muffler and prop. But from a performance standpoint, the 1/4 wave "muffler" (tuned pipe) is really in the same performance class as the 1/2 wave pipe.
Am I correct in this understanding of the SPA rules? Anyone care to clarify/justify this reasoning?
I believe it IS legal to use the stock muffler that comes with the Jett 2-stroke engine. The key is that it is a standard muffler for that engine, rather than an aftermarket item that is purchased to boost performance. That being said, the Ultrathrust, (if that is the right name) muffler has been allowed since it's still a muffler even though it is technically an aftermarket muffler. It's a grey area.
I think the main thing is that a long tuned pipe is obviously an aftermarket item.
I'll ask a couple of the SPA Board members to verify what I'm saying.
Duane