New Kitfox 4 912 muffler

[avidflyer]

A couple of months ago, my muffler cracked again where the tailpipe comes out of the muffler. I talked to Kitfox, and they gave me the number to Experimental Aircraft Exhaust in Lake City, Mn. I ordered one, and never heard another word till two days ago. I had kind of forgot about it, as I had got mine welded back up with some braces to the tail pipe and it's been fine since. Anyway, they said it was ready to ship. It showed up yesterday, and here it is. Base cost was $750, at my door with sales tax and shipping was $839. Anyway, it looks good, it's made to fit the standard Kitfox motor mount style for the model 3 and 4 that uses the four arms to bolt to the engine. I do wish I had made them put a brace between the tailpipe and the muffler though. JImChuk

[Dusty]

Just a thought
Having struggled with various 912 muffler issues, mostly broken stinger welds. We got serious and pulled some apart.
The kitfox had remnants of an internal support. We rebuild them now with a full length perforated pipe that is supported at the far end by a slip joint to allow for different expansion rates. I assume this is the current way the mufflers are built? 500+ hrs on mine no problems

[avidflyer]

That slip joint sounds like a good idea. Actually building these mufflers should be fairly easy if one can weld the stainless. Especially if you had one to copy. Hardest part would be getting the inlet pipes in the right place and at the right angle. Wouldn't be that hard to make a jig that would located the holes if you already have a muffler to copy. JImChuk

[Spook712]

Do they have the measurements for the Kitfox exhaust system, pipes and muffler?


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[avidflyer]

Do they have the measurements for the Kitfox exhaust system, pipes and muffler?


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If that question was addressed to me and in regard to Experimental aircraft exhaust company, yes they had all the measurements for the muffler. Not sure on the pipes. Here is a link to their website. JImChuk
Experimental Aircraft Exhaust Systems and Aircraft Exhaust Components (experimentalexhaust.com)

[Av8r3400]

Just a thought
Having struggled with various 912 muffler issues, mostly broken stinger welds. We got serious and pulled some apart.
The kitfox had remnants of an internal support. We rebuild them now with a full length perforated pipe that is supported at the far end by a slip joint to allow for different expansion rates. I assume this is the current way the mufflers are built? 500+ hrs on mine no problems

I have had two of the "internal slip joint" mufflers fail. The first on my 912UL powered 4-1050, the second on the Mangy Fox. I have the second on my bench waiting to be disassembled for autopsy and possible rebuild.

I still believe the failure point in the design is the sleeve joints from the muffler to the header pipes not allowing for any movement. Every other system I have seen have utilized ball and socket type joints.