Muffler Life

Jeff Oslick

Jeff Oslick

Final Approach
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Jeff Oslick
Our 182 (Continental/Pponk O-470-50) seems to like to erode/blow out muffler internals at a fairly rapid rate. To date we've been using Knisley mufflers, and have Knisley stacks, which seem to be holding up fine, but the muffler internals start falling apart after about 250-300 hours.

Anyone with a big-bore Conti having better luck?
 
That's not normal. What EGT you tend to run?
 
I found this article while researching your complaint.
https://backcountrypilot.org/forum/best-exhaust-for-o470-11848
The 10th post talks about a lifetime exhaust from Lee.

My question to you is have you discussed your problem with a Knisley product engineer? I find it hard to believe 300 hours to muffler failure would be considered acceptable service life from their point of view. They may have suggestions that can help. If not, then I'd be looking for something from another manufacturer that is designed to last longer.

One Miracle at a time! I hope this helps
 
Leading Edge Exhaust Systems has been bought by Power Flow and are now providing new exhaust systems for the O470 if I read their literature correctly. I think they have a 1 year unlimited hours warranty.

I am interested in this because I have considered it as an upgrade when my Mooney needs a new exhaust. I don't need a new exhaust yet, and it doesn’t make sense to upgrade until I have to spend money on the exhaust anyway. You don't have that problem as your exhaust needs service now.

https://www.aviationconsumer.com/maintenance/best-aircraft-exhaust-systems/

https://sites.google.com/powerflowsystems.com/powerflowsystems/six-cylinder-cessna-exhausts
 
We switched to the Acorn mufflers without baffles on all our 180/185's. Can't blow them out if they're not there in the first place.
 
The more I dig into this, the more it seems that 300-400 hours life for the baffles is fairly common. Most of the manufacturers offer the 1 year unlimited hours warranty. I guess they can do this safely because there aren't that many planes that fly that many hours per year.

A contributing factor for us this round may have been some bad chemistry mixing in with the heat. We just pulled a couple cylinders for low compression with a lot of blow-by past the rings (appears to all be rings, not valves, mercifully). Don't know exactly what that would add to the exhaust mix but imagine it isn't healthy. Oddly, our oil analysis didn't really show elevated lead from the blow-by.
 
tyndall said:
We switched to the Acorn mufflers without baffles on all our 180/185's. Can't blow them out if they're not there in the first place.
Click to expand...

I was thinking the same thing - though not sure if that is an option for our 182.
 
Yes, it's a common issue on the 182 for sure. What year do you have? Cessna kept changing the carb-heat setup in the mid 60s so some of those models have a muffler unique to a single model year. Can mean trouble finding a replacement without long lead times. If your IA is picky and unsympathetic to the situation, they will make you toss a perfectly functional muffler. You could argue that they are safer once the flame cones have blown out, since the main danger is a big piece breaking off and restricting the outlet. Once they're gone, the danger has passed.

The Acorn model without cones would be a great option, but just be aware that it might not fit up perfectly to the Knisley stacks. Guess it wouldn't hurt to try.

C.
 
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