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Thread: PA-22 Chin scoop baffle seal

  1. #21
    Subsonic's Avatar
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    Default Re: PA-22 Chin scoop baffle seal

    Walt, If I'm not mistaken, and that does happen, your mystery scoop is an air intake for your muffler heater. It's on the left side of your lower cowling, and inside the big large mouth bass intake. A scat tube should pass to the left of your carb and be attached to your muffler shroud. This is a fairly important piece of ductwork to cool the muffler and then pump warm air to the cabin when you open the cabin heater vent. To me, it looks like you need a new one. And you need a piece of scat and a couple hose clamps. Others with more knowledge will tune me up if required. Keep up the good work.
    Last edited by Subsonic; 05-15-2020 at 10:21 PM.

  2. #22
    walt.buskey's Avatar
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    Default Re: PA-22 Chin scoop baffle seal

    OK, so I'm scratching my head...again...

    This is what I have on my plane; the only change I've made so far is to switch carb heat and rear cabin heat scat tubes to their correct locations (they were reversed):

    A) INLETS - First pic
    1. Muffler shroud has one inlet on its top, elbow muff has one inlet on its top.
    2. Those two inlets are connected via two scat tubes to two stubs which are located on the right side of the rear aluminum baffle.

    B) OUTLETS - Second pic
    1. Elbow muff is connected to a welded-on section of the exhaust header, which has one outlet on the bottom; that's (now) connected to the carb air box.
    2. Muffler shroud has two outlets on its bottom; one is connected to the (optional) rear cabin heat box -- the one right at the lower edge of the firewall -- and the other, via a very short scat tube, is connected to the front cabin heat box (located immediately above the rear heat box on the firewall).

    In the parts book, page 171, is a diagram of the muffler & scat tubes. At the bottom of the muffler shroud it shows the two outlets; one section of scat tube says "TO BOTTOM COWL" (presumably to our mystery scoop thing?); the other scat tube is labeled "TO REAR HEATER BOX OR CARBURETOR AIR BOX" ... but nothing indicated for the front heat box. ???

    I'm at a loss here, folks.... anyone have an idea of what's not correct on my plane? TIA for any help!

    Walt

    DSC08447.jpgDSC08242.jpg parts book scat tube diagram.jpg

  3. #23
    Administrator Steve Pierce's Avatar
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    Default Re: PA-22 Chin scoop baffle seal

    The bottom scoop in your lower cowl is pressure air to the left side of the muffler shroud. Item 19 "To Lower Cowl".

  4. #24
    walt.buskey's Avatar
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    Default Re: PA-22 Chin scoop baffle seal

    I do see that in the drawing, Steve. There, on the left bottom of the muffler shroud, is where my front cabin heat connects with that real short piece of scat tube. Wouldn't that then create (?) two pressure-air connections to the muffler shroud?

    If I remove that and run scat tube from the muffler shroud to the chin scoop scoop-fitting, then what do I connect to my cabin heat (front)? Or am I perhaps missing some sort of scat tube "Y" connection?

    Any pics of how it's set up on Cathy's T-P?
    Last edited by walt.buskey; 05-16-2020 at 08:50 AM.

  5. #25
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    Default Re: PA-22 Chin scoop baffle seal

    The muffler is devided into two chambers, there is a baffle in the middle on the outside of the muffler can. The top intakes are providing pressure to the right side and to the carn heat elbow muff. The chin scoop pick-up is providing pressure to the left side.

  6. #26
    walt.buskey's Avatar
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    Default Re: PA-22 Chin scoop baffle seal

    OK, at last I understand it!

    I knew there was a muffler shroud brace/support ridge in the center of the muffler (at least that's what I thought it was), but it never occurred to me that it also served as a DIVIDER, separating the space between the muffler and its external sleeve into TWO chambers.

    NOW it makes sense why that chin scoop would be ducted to the scat tube connection on the left side. Once again, thank you, Steve!

    Only question I now have is how does warmed air get to the front cabin heat/defroster air box? Page 173 does list a tube, #16 in the drawing, part #10525-18, that's called "HOSE- Muffler to cabin heat box front seat" but I can't see where it connects to the muffler & shroud.

    I'll be looking closely the next trip down to the field!


    front cabin heat box.jpg

  7. #27
    walt.buskey's Avatar
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    Default Re: PA-22 Chin scoop baffle seal

    Chin scoop baffle is coming along; did an experiment with one of the small side pieces and it seems to work, so now I can duplicate that on the other side, mount the baffle & seal(s) in position between the nose gear frame tubes and be done with it. That'll be one more thing completed!

    DSC08528.jpg DSC08530.jpg

    OTOH, it's still a mystery how the "cabin heat, front" connects to the muffler shroud. There's only that one connection on the bottom of the left (pilot's) side, where a scat tube should apparently connect from my "mystery scoop" in the chin cowl. No way for warm air to get out (and go to the front heat air box) that I can see.....

  8. #28
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    Default Re: PA-22 Chin scoop baffle seal

    Quote Originally Posted by walt.buskey View Post
    OK, at last I understand it!

    I knew there was a muffler shroud brace/support ridge in the center of the muffler (at least that's what I thought it was), but it never occurred to me that it also served as a DIVIDER, separating the space between the muffler and its external sleeve into TWO chambers.

    NOW it makes sense why that chin scoop would be ducted to the scat tube connection on the left side. Once again, thank you, Steve!

    Only question I now have is how does warmed air get to the front cabin heat/defroster air box? Page 173 does list a tube, #16 in the drawing, part #10525-18, that's called "HOSE- Muffler to cabin heat box front seat" but I can't see where it connects to the muffler & shroud.

    I'll be looking closely the next trip down to the field!


    front cabin heat box.jpg
    Look at your picture in the previous post. It is that short hose between the bottom of the muffler and the cabin heat box. The defroster is a Y tube in front of the cabin heat box.

  9. #29
    walt.buskey's Avatar
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    Default Re: PA-22 Chin scoop baffle seal

    Yes, I'm pretty sure we have the scat tube to the front cabin heat box correct.... but we MAY have solved the mystery -- again, something that I'd seen before but it didn't register.

    There's a "patch" on the extreme left edge of the shroud that looks like that's where the chin-scoop scat tube should connect. On the SWPO drawings CD, the front view shows where that stub ought to be located, with the chin-scoop scat tube attached.

    Next order of business is to see what's under that patch, but I expect we may find a nice, round hole where a scat tub stub used to be. At least I hope so.

    To be continued....

    Here's the CD drawing...scat & baffles- front view.jpg ...and the "patch" on the underside of my shroud: DSC08533.jpg You can just see the short tube connected to the upper (front seat) cabin heat airbox behind that fuel line, just to the left of the patch.

  10. #30
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    Default Re: PA-22 Chin scoop baffle seal

    I think you found your smoking gun.

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