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Thread: Muffler Shroud - Carb Heat <> Cabin Heat Separation

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    Muffler Shroud - Carb Heat <> Cabin Heat Separation

    Hello folks, potentially naïve question, is the muffler shroud on a PA-18 segregated into two compartments or could back fires potentially blow into the cockpit if the carb heat were on and cabin heat use partially impact carb heat effectiveness?


  2. #2
    Steve Pierce's Avatar
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    The heat shroud has a center baffle, ring welded around the outside of the muffler. A muffler backfire will not effect the carb heat or cabin heat unless you blow a hole in the muffler.
    Click image for larger version. 

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    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  3. #3

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    ...which is why there is a clamp band over it.. Thanks Steve. Should have found a photo of a muffler first.

    One more question on the cabin heat box if I may. Is it a mixer or just a flap. Wondering what the hole open to the (not always fresh) undercowl air is for?

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    Last edited by Flow; 06-23-2022 at 09:10 PM.

  4. #4
    mvivion's Avatar
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    Quote Originally Posted by Flow View Post
    ...which is why there is a clamp band over it.. Thanks Steve. Should have found a photo of a muffler first.

    One more question on the cabin heat box if I may. Is it a mixer or just a flap. Wondering what the hole open to the (not always fresh) undercowl air is for?

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    Or with a Penn Yan

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    The whole point of that shroud around the muffler is to capture heat, so it can be used for cabin heat or for carb heat when needed. But, when those tasks aren’t needed, that shroud is still gathering heat. When you close the cabin heat control and the carb heat control, that heat is exhausted out that opening, helped along by some intake air which pressurizes the air going through the shroud. That prevents dangerous heat buildup of the muffler.

    MTV
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    Everyday is a school day, thanks guys.
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