ORIGINAL: rainedave
Ok, lots more data on the SK .70 muffler. The weather was cool and very damp, actually foggy at the field. This probably has some impact, I guess.
Today I ran my ABC(N) SF .61 with both the SK and the stock mufflers. The SK is a dud. Not at all what I was hoping for. Also, my ringed version is stronger than the ABC. I wasn't expecting that, either.
Here's what I recorded.
Power master 10% with extra castor added.
SK .70 muffler:
APC 11x11 - 9400
APC 11x10 - 10960
APC 12x6 - 11710
APC 12x8 - 10630
Stock muffler:
APC 11x11 - 9730
APC 11x10 - 10720
APC 12x6 - 12130
APC 12x8 - 10750
You can see that the stock muffler actually has a slight edge. Believe it or not, it is noticeably quieter, too (but still pretty loud).
The good news is that the SK is about half the cost of an OS #744B, so, if you need a replacement it's an option.
I still want to run more tests on the ringed engine, but I had to leave the field.
David
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Mufflers, like engines, work best when following the old addage, "There's no replacement for displacement". <G>
Ed Cregger