Optional rear heat muff

[Harold Kroeker]

I've been following this thread with interest because I am looking for a way to get more cabin heat in my Clipper. Where does the air enter the the heat shroud that goes over the exhaust pipe on the right side?

[smcnutt]

From the baffle directly above. The scat tube in this picture was a little too long and we've since shortened it.
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Don't have a picture but the output comes out of the bottom of the heat muff and goes into a diverter box on (I think) the carb heat box.

[Steve Pierce]

I've been following this thread with interest because I am looking for a way to get more cabin heat in my Clipper. Where does the air enter the the heat shroud that goes over the exhaust pipe on the right side?

This is heat for carb heat since the joint between the exhaust pipe and muffler leaks. Could be used for carb heat and use the other side of the muffler like the Pacer and Tri-Pacer for back seat heat. Move to Texas in the winter, problem solved. I have plenty of things to keep you busy and I am sue you and darrel can talk S21 Outbounds as well.

[walt.buskey]

Hello, Harold! I'm not at my plane, but here's an older pic I took some time ago of the right side. As you can see, very much the same as mcnutt's. I believe the lower forward scat tube goes to the carb heat box on my PA-22, but not 100% sure. Note in the Piper parts diagram above that one of those tubes coming off the muffler shroud (#6-#19) can go to either the carb heat OR rear cabin heat...

Next time I'm down at the hangar, I'll get a better pic.

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[walt.buskey]

OK, went down yesterday and looked closer:

1) the two high-pressure air intakes are front and center on the rear engine baffle;
2) one of those goes to the $500 heat muff pieces;
3) the other, on my PA-22, goes to the top of the stainless steel (?) shroud that surrounds the muffler, apparently the same as mcnutt's.


From the bottom of the muffler shroud, there are two outlets:
1) on my plane, the right-side scat tube goes to the carb heat control box;
2) the left side, a very short one, goes to the front cabin heat/defroster control box (this is the upper of the two cabin heat control boxes)

The last scat tube comes out of the welded-on "can" on the forward right exhaust header (connected to the aluminum heat muff) and goes to the rear cabin heat control box (the lower one, just above the bottom of the firewall).

Not sure if this is "right" or not, but that's the way it is.


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[Steve Pierce]

The proper routing is depicted in the parts manual and the engine installation drawing. The right elbow type heat muff can get exhaust gasses leaking between the muffler and exhaust pipe joint and is used for carb heat. The muffler is one piece with no joints for exhaust gasses to leak from unless the muffler can is cracked/corroded. DO NOT USE THE RIGHT SIDE ELBOW HEAT MUFF FOR CABIN HEAT. Piper used the elbow type heat muff for cabing heat in the 90 hp Super Cub but the ehaust pipe is welded to the muffler so the can be no leaks.

[walt.buskey]

Thank you, Steve -- that's kinda what I was thinking, too. I will switch those two scat tubes around -- rear heat box tube moved to carb heat box and visa versa.

[Harold Kroeker]

OK, went down yesterday and looked closer:

Thanks for taking the time to get those pictures for me and for the detailed explanation as well.

[walt.buskey]

You're welcome, Harold. Just take note of Steve's comment, as mine was definitely set up incorrectly.

It would have been nice if that were clearer in the diagrams... like, "Use the upper/lower heat muff when optional rear heat is used, BUT USE ITS OUTLET FOR CARB HEAT ONLY and the (former) muffler shroud carb heat outlet for the rear heat"... or something like that. I see now how they tried to diagram it and why it's labeled "CARBURETOR HEAT OR REAR HEAT" in the inset diagram. That "OR" is a tad misleading, unless you know better. Live & learn. Nice that Steve's around to keep me straight!

PS: any more instances of getting locked into a sleeping bag by ice on the outside?? (I'll never forget that!)

[dgapilot]

Don’t know that the rear heat was optional. Perhaps on the PA-20, but i think all PA-22s had it.


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