Replacing muffler

[Shiroyuki]

During a recent inspection my M20J’s muffler flame tube was found to be broken, and my mechanic suggest to replace it.

The mechanic who found the broken flame tube says the riser and tailpipe need to be replaced at the same time, while my regular mechanic says he would just replace the muffler.

I don’t really know who’s advice to follow so looking for some input.

thanks

[Ragsf15e]

5 minutes ago, Shiroyuki said:

During a recent inspection my M20J’s muffler flame tube was found to be broken, and my mechanic suggest to replace it.

The mechanic who found the broken flame tube says the riser and tailpipe need to be replaced at the same time, while my regular mechanic says he would just replace the muffler.

I don’t really know who’s advice to follow so looking for some input.

thanks

There are a few other threads on this (try some google searches with mooneyspace and flame tube), but it’s going to be at the discretion of your IA.  Many are fin with missing flame tubes. Mine hasn’t had one in several years. That being said, you should ensure there are no leaks, especially around the heater muff as that can become dangerous.  If it’s simply the flame tube, you might want to consider just keeping an eye on it.

[EricJ]

The inspection criterion for the flame tube in the M20J Service Maintenance Manual is that there aren't any pieces of it blocking the exhaust outlet.   I'm another one that has no flame tube left in my muffler...it's entirely gone.   The purpose of the flame tube is to dissipate some of the energy of an after-fire (aka backfire) to reduce the likelihood of cracking the muffler.   I just inspect mine closely after any backfires, which are pretty rare.

I agree that your IA's opinion is the one that matters, but it's useful to arm yourself with some alternatives and other practices.  You certainly have options.

[Shadrach]

I have been hesitant to say this and I can't prove it, but I have a sneaking suspicion that an overhauler that I will not name (no longer in business), may have sent overhauled/exchange mufflers to customers without flame tubes.  Boroscope inspection of my muffler shows no evidence that tubes were ever present.  I have seen mufflers with deformed flame tubes. I have seen mufflers with cracked or missing sections of flame tube or even just a few jagged remnants of a flame tube. This is the first that I have seen flame tubes that were either never installed or completely disappeared without a trace. The internal seams where the exhaust pipes enter the muffler are clean.   That has been the case ever since I started doing internal inspections about 8 years ago. Muffler has been in service for 1000hrs but has not changed internally since we started the internal inspections about 400hrs ago. 

[PT20J]

Ross, given the short time they seen to last, that might have been a design improvement. 

[EricJ]

1 hour ago, PT20J said:

Ross, given the short time they seen to last, that might have been a design improvement. 

I'd have marketed it as something like "block-proof open flametube technology" or something like that. 

[Shadrach]

2 hours ago, PT20J said:

Ross, given the short time they seen to last, that might have been a design improvement. 

No doubt. I think Piper came to the same conclusion as they omitted flame tubes on the Comanche exhaust at some point.

[Shiroyuki]

Thanks for your reply!

I just talked to my mechanic over the phone today and he says if the flame tube is completely gone, he is ok with it. If there's any remaining flame tube inside his suggestion would be to change the muffler, since it risk blocking the exhaust. I think it make sense.