MACS one piece mufflers?

Has anyone used the MACS one piece mufflers? What are the dimensions? How well do they quiet the exhaust? How much do they affect the power? Any general comments?

A bunch of us have used the Mac's Muffler (you might try a search on SSW's main forum). This is a tuned pipe of sorts, and works nicely if you follow a few basic rules. The #6650 fits Tower .40, OS .40FP, .40/.46LA, but the length is significant, and can interfere with fuselage mounted LG on profiles, or the wing on upright/inverted installations. It isn't difficult to bend the stinger a little, if needed.

There are some good & bad things about this setup. The only downside, other than the looks (which some may find offensive), is that you have to launch at 10k, and be a bit rich on top of that, so figure a peak of at least 11k to 11.5k. That means you can't run too much prop, especially pitch must be 4" or less for most setups, if you are trying to fly stunt. The 11.5 x 4 APC is a good baseline prop for the OS .46LA, 11 x 4's for .40's. When the rpm is correct, the pipe has a rattling sound like the muffler or wheels are falling off. Noise isn't as bad as a tongue muffler, tho not as quiet as a stock OS muffler. You can open up the stinger diameter a little, for some extra umph, but I haven't done that. If you have to carry your model any distance, the pipe makes a great handle. The #6650 weighs almost exactly 2 oz., and some of that is aft, so may help with CG issues. If your landing gear won't work with big prop diameters, this is a good setup. It does seem to regulate the speed on the downstrokes of the maneuvers.

Fuel economy is excellent. I ran a variety of fuel mixes in my .46LA, with no real noticeable changes between Powermaster 10-22 GMA (half & half synth and castor) and 10-29 GMA (29% Castor). The worst thing you can do is over-prop, otherwise it's as simple a setup as you can get, but you do need a tachometer. Right now, I'd say to get a Magnum tach, from Hobby People, because the TNC tacho appears to be out of production, or only available in small batches. Steve