How to prevent cracked muffler on 912uls

[Rodney]

I thought the muffler was made of a 304 stainless - but am not absolutely sure. What I do know is that I welded my muffler cracks with 308 stainless wire on a MIG welder and it has held so far.
I just got a TIG welder and am going to weld in an Air/Fuel bung into the muffler this week. I'll still use some 308 filler rod for the weld.

Regards
Rodney

[AvDES LLC]

good to hear you’re taking the leap of tuning faith with the AFR. I actually spent the evening putting together a bit of code to help make this process a bit more user friendly and cost effective. Please keep us posted with the initial readings as well as any adjustments made and their results!

[AvDES LLC]

Anyone have an old exhaust they will soon be replacing or sitting on a shelf?

Im half tempted at this point to get an old exhaust can, cut the muffler in half and install a plate in the middle to divide the two engine banks. Then installing an AFR meter on each side will allow for tuning of each carb independently of one another for some very very fine adjustments to see what kinda power can really be pulled from these stock engines - I think tuning to an average is good, but independently would really allow for an understanding as to what each side of the engine is doing with the fuel being delivered without the crossover tube.

[Eric Page]

I have a new, unused exhaust system for a 912UL/ULS, including down-pipes with cylinder flanges and muffler with welded-on stinger. It dates from 1995. No springs or other hardware. I'd take $775 plus shipping. Not interesting in parting it out.

[AvDES LLC]

thank you and if I end up not finding an older clapped out exhaust to cut up, this may be an option. Trying to not destroy new/functional parts if at all possible

[Delta Whisky]

Anyone have an old exhaust they will soon be replacing or sitting on a shelf?

Im half tempted at this point to get an old exhaust can, cut the muffler in half and install a plate in the middle to divide the two engine banks. Then installing an AFR meter on each side will allow for tuning of each carb independently of one another for some very very fine adjustments to see what kinda power can really be pulled from these stock engines - I think tuning to an average is good, but independently would really allow for an understanding as to what each side of the engine is doing with the fuel being delivered without the crossover tube.

Have you given any thought to putting an O2 sensor in one of the headers - one on each side of the engine? Probably would have to go in the forward cylinder exhaust pipes to meet the distance requirements (exhaust valve to sensor) - if they are long enough.

[AvDES LLC]

i have, however you hit the mail in the head with my worry. The sensors have a warning that is very clear to keep them below 1600*F. I’d be worried I’d kill sensors with a quickness.

[Delta Whisky]

Interesting. Just checked a few of my logs and have yet to see any temps above 1450. I'll measure (maybe) tomorrow and check the distance from the end of the exhaust pipe/cylinder head.

[AvDES LLC]

would appreciate that. Interestingly the only time I’ve ever approached the 1400 temps is when I was seeing that extreme lean condition tapping out at around 14.9 to 15.1 to 1 on the AFR. You at all planning to check your ratios during flight and seeing where your engine is at as far as mixture goes?

[Delta Whisky]

Ahh, such a creature of habit. I'm so used to thinking there is an airplane at the airport that I spoke before thinking - the airplane is at the hangar, but the headers are at Kitfox helping in the build of a new muffler. So, measurements aren't available - at least from me. I'll guess that there is a good possibility that my temps are higher because I took them at a much lower altitude. (about 2,000 ft msl)

And I do plan to install an AFR gauge when the muffler makes it back. I am curious to compare my experience and numbers to yours.