MUFFLERS ON RV EXHAUST SYSTEMS Good and Bad

[rv969wf]

I read thru some past postings about exhaust/mufflers etc. Someone even mentioned about "Supertrapp" mufflers or cherry bomb glasspacks,,,,etc..etc.
This is my past experience with one style of muffler on my -6. I started out with a Vetterman crossover exhaust in 1999. Noisy?? not to bad. I wanted a little more peace and quiet in the cockpit so I kicked around the idea of hanging two Supertrapp Mufflers on the Vetterman exhaust, so I purchased at close to $200 each for a pair from Summit Racing, stainless steel to boot but not 321 stainless, heavy yes. I have used Supertrapps on my Alcohol Sprint cars with no problems other than a repack of the fiberglass once a season and they held up quite nice. Airplanes are a different story. Within 10 hours flying time on my -6 all of the glass packing was burned out along with the diffuser discs cracking and falling apart. They will not hold up to the constant high EGT's. Another problem is that they are not 321 stainless. Something else I noted with them was that when the glass packing started to melt, it turned into solid chunks of glass and nearly plugged up the round diffuser discs at the outlet. I found this out with EGT's getting erratic. DO not use them on an aircraft unless you baby the thing and putter around at low power. Were they quiet?? YES, very quiet the first few hours and I knocked off 6 DB of noise inside the cockpit for the first few hours until they failed. I would suggest, but anyone can do what they want, "Glass packed mufflers will probably not last on an airplane" with EGT's running at max all the time. They will be quiet at first then burn out the glass packing later. I only wanted to share my experience with the Supertrapp Mufflers I tried. Happy flying, Alan

[airguy]

Another thing to consider - LOP operation will make this problem even worse, as the exhaust gas stream will contain sufficient oxygen to support combustion (slow, but still there) of the epoxy matrix holding the fiberglass together once it warms up to operating temperature. Glass-packed mufflers were NOT designed to operate in an oxygen-rich (read - not completely oxygen deficient) atmosphere. 99.99% of land vehicles operate under ROP conditions at any decent power percentage, where high EGTs are present, and certainly don't run at max power for long enough periods of time to raise the muffler to peak EGT temperatures, where epoxy ignition could occur. LOP operation at significantly reduced EGT's would probably work, but you'll never see low enough EGT's in an aircraft (unless it's diesel) to be safe from this one....