I recently bought a Bisson muffler for my 3W-35. Based on the test run of the engine (Zinger 18 x 10 @ 6600 RPM), I was wondering if my muffler was restricting the performance any. The open area at the exhaust port is .6 square inches. The open area at the exit of the muffler is only 42% (.25 square inches) of the exhaust port open area. Shouldn't this be around 60% or so?? The ends of the exhaust a rolled to a smaller diameter than the ID of the pipes. The rolled ends could be cut off to allow for greater open area at the exit of the muffler.

Your thoughts?

Ryan