ORIGINAL: CGRetired
I had an OS 46 with that Macs muffler. It was excellent. It was on a plane bought as a ''club trainer''. It really wasn't a plane that needed a muffler like that, but it worked out just fine. The engine ran well and had lots of power
CGr.
I had used the same original black muffler on both the 46FX and 55AX. The performance was ho-hum on the FX and lacking on the AX. I figured it was a good replacement for stock that wouldn't vibrate apart, also the plane for some reason or another seemed to have less smut on it (air stream more laminar?) , but no real perceptible power gain. Several guys now tell me the new larger volume black muffler works a lot better (55AX), but I have yet to try it myself.
The next level up are called "tuned" mufflers, such as Ultrathrust (discontinued) and the Jett-stream mufflers.
Be warned, some "tuned" mufflers can really add power and speed to the point that you exceed the plane's (trainer?) designed operating envelope and the plane's control surfaces can go into "flutter". This can quickly destroy the plane. Example: Kadet L-T40, whole horizontal stabilizer flutter or World Models Skyraider I and II strip aileron flutter using an OS 55AX ,Ultrathust muffler and Master Airscrew 11X7 S-2 series prop. With stock muffler/baffle these planes were fine. Some "tuned" mufflers can also have poor mid-range and transition characteristics.
ORIGINAL: Gray Beard
I have never noticed a nickles worth of difference but I only tested with the OS .46La engines. I used several of them during my fun fly days, the LAs. I did remove them from all my engines though but just because of vibration and the gray slime that comes out of the muffler when the baffle gets loose. Other then that there is no reason to remove them. I think this would be a good question for Bill Baxter from OS factory support? I know I never did any serious testing and no longer have any of the small engines with that type of muffler.
I had a Evolution 46 NT on a Quickie. It ran best with the baffle in, but the baffle gets loose and beats itself to a pulp, I recall the gray silver slime.