Today I tried the Mac's muffler with the exit opened to 15/32". First I ran and flew the Supertigre Bluehead with the Dubro baffle plate muffler. Ran and flew very well. The engine turned 12000 RPM with a Zinger 12x6 prop. Then I put the Mac's muffler on. The engine would only run 10500 RPM with the opened up Mac muffler. About 500 RPM more than the stock size exit opening. When I flew the Aeromaster with the Mac's muffler on there was a difinate lost in flight performance due to the lower RPM. I have currently given up on trying to make the Mac's muffler work on this engine. Some day I hope to try a new Supertigre 60 muffler on the Bluehead but that is going to have to wait. I'm tired on messing with mufflers and want to get some flying in. I will have to put up with the little bit of extra noise of the Dubro muffler.
Ralph White, Neoga, IL