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Thread: More Heat From Stock PA12 Exhaust

  1. #1

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    More Heat From Stock PA12 Exhaust

    Any suggestions on a way to get more heat in my pa-12 with 100hp o235 engine? It's cold up here in MN!

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    cubdriver2's Avatar
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    Quote Originally Posted by twl View Post
    Any suggestions on a way to get more heat in my pa-12 with 100hp o235 engine? It's cold up here in MN!
    Putting it where you can feel it helps a lot



    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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    Looking for some input here on how to get more heat in the cabin from my 235 100HP. I have some pictures of my exhaust/engine. Yes, I have been testing restricting air through cowling to keep CHT above 300F since our cold snap of -10F here in MN is making me hanger stir-crazy.

    Different exhaust?

    Pa-12 lycoming 235 w/no oil cooler.

    Any ideas or suggestions that donít cost as much as upgrading to a 320?










  4. #4

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    Thats sure a different exhaust pipe arrangement then what I have on my pa11 with a o-235, mine has about 10-15 feet of exhaust pipe running around the engine, how is your oil temp in the summer.
    You could try wrapping the exhaust pipe with exhaust pipe wrap that would get more of the heat to the muffler, I dont know nothing about the legality of the wrap.

  5. #5
    Bearhawk Builder's Avatar
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    4th pic down shows a scat tube from a scoop on the right side to your air box, that could be blowing a lot of cold air. Try blocking that one off.
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    skywagon8a's Avatar
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    Quote Originally Posted by twl View Post
    Looking for some input here on how to get more heat in the cabin from my 235 100HP. I have some pictures of my exhaust/engine. Yes, I have been testing restricting air through cowling to keep CHT above 300F since our cold snap of -10F here in MN is making me hanger stir-crazy.

    Different exhaust?

    Pa-12 lycoming 235 w/no oil cooler.

    Any ideas or suggestions that don’t cost as much as upgrading to a 320?
    Have you tried restricting the cooling air exhaust opening? This will slow down the passage of air through the engine compartment allowing it to get warmer. Some airplanes have cowl flaps for this purpose. You could use your duct tape.

    Also as dryfarmer suggests you could wrap the shroud around the muffler with an insulating materiel to help retain the heat. You are likely loosing heat there. Also you could wrap the muffler with screen door spring to help with the heat transfer.
    N1PA

  7. #7
    Eddie Foy's Avatar
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    Springs around the muffler and inside the shroud should help. Sutton uses a similiar technique.
    "Put out my hand and touched the face of God!"

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    Steve Pierce's Avatar
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    That looks like a PA12 I use to know. Where is the intake air coming from to pressurize the heat shroud around the muffler? I think I would remove the fresh air SCAT hose to the heat box for winter ops.
    Steve Pierce

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    Eddie Foy's Avatar
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    How will you get flow if you do that?

    Quote Originally Posted by Steve Pierce View Post
    That looks like a PA12 I use to know. Where is the intake air coming from to pressurize the heat shroud around the muffler? I think I would remove the fresh air SCAT hose to the heat box for winter ops.
    "Put out my hand and touched the face of God!"

  10. #10
    Steve Pierce's Avatar
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    Quote Originally Posted by Eddie Foy View Post
    How will you get flow if you do that?
    I am talking about the SCAT hose shown on the right side engine photo that runs from a scoop on the bottom of the cowling to the cabin airbox. It is suppose to bring cool air into the cabin. When the heat is on cold air is still coming up to the box. The box doors leak terribly so I imagine the cold air is leaking around and effecting the heat output.
    Steve Pierce

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    PerryB's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I am talking about the SCAT hose shown on the right side engine photo that runs from a scoop on the bottom of the cowling to the cabin airbox. It is suppose to bring cool air into the cabin. When the heat is on cold air is still coming up to the box. The box doors leak terribly so I imagine the cold air is leaking around and effecting the heat output.
    Agreed. Get rid of the cold air vent tube. Also, the pressure/supply tube is coming from the front baffle and is now blocked by the inlet being taped off.
    After Monday and Tuesday, even the calendar says WTF !

  12. #12

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    It appears the fresh air scat attaches to an inlet on the right bottom cowl. It would be simple to plug the right intake to reduce cold air. If that works? Fix the heat box door. You could unblock the left nose cowl intake for sure. Maybe swap the nose inlet scat to the fresh air supply and the right lower cowl inlet to pressurize the cabin heat. And if that isn't enough re-route the left side and add a heat robber on the exhaust stacks.
    Last edited by stewartb; 01-03-2018 at 09:41 AM.

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    Stewart, the left side of that system is carb heat. There is a baffle around the middle of the muffler and that heat shroud assy. is effectively split into two separate systems. The cabin heat supply is from the right front baffle, post#3/pic.#2.
    After Monday and Tuesday, even the calendar says WTF !
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    I saw that and amended my comments.

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    Should have stated I have blocked off the fresh air line going into the "mixer box". This has helped, but still isn't much warmer.

    PerryB, do you think that ram air intake needs to be open for positive pressure (volume) into the cabin?

    Annual is next week. I may try to get some heat tape on those stacks.

    ? 3rd pic down is left side of engine. The tube bringing fresh air into the exhaust shroud. Should I swap it with the one coming from back of engine just behind the cylinders? That hose is just hanging blowing on oil filter it seems.



    More detail in this picture.

    To respond, no I have not yet blocked cowling exhaust/vent openings. Just trying to make things as effecient as possible before stuffing "cheeks" or other measures.


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  16. #16
    PerryB's Avatar
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    If the tube coming off the left rear baffle is just hanging then yes, make it your supply line to the cabin heat (right) side of the exhaust shroud. Under normal circumstances any unused SCAT tubes should be plugged/capped, but in those temps I don't think it matters.
    After Monday and Tuesday, even the calendar says WTF !
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  17. #17
    nanook's Avatar
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    Open up the heated air outlet into the cabin, your scat hose is blocking off 30% of your heat air volume. Take the fresh air scat hose and hook it up to the muffler heat inlet. Block off the fresh air inlet to the cabin air box. You have blocked/taped over your air into the muffler heat inlet so disconnect and tie wrap the end. Your square air mixing box is a disaster for air flow for cabin heat. Square peg for a round hole?
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    Charlie Longley's Avatar
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    Buy a Sutton exhaust, problem solved! More heat than I’ll ever need.

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    Great advice so far. If you look at the firewall on the inside it looks like at one time the plane had another air input. Stick fresh air input in that hole and get rid of that fresh/hot air box from hell that someone stuck on it. It may have sounded like a good ideal at the time but as you can see it sucks. On a bit of thread drift if you are flying at -10 degree temps you should be dressed for -10 degree temps in case you have to walk home. Do that and you won't need so much cabin heat.
    DENNY

  20. #20

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    Quote Originally Posted by Charlie Longley View Post
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    Buy a Sutton exhaust, problem solved! More heat than Iíll ever need.
    Is that Sutton on a 235? Itís very much different from my current setup with the muffler forward of the carb.


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  21. #21

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    Quote Originally Posted by Charlie Longley View Post
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    Buy a Sutton exhaust, problem solved! More heat than Iíll ever need.
    Denny, completely agree on dressing for the flight/survival. One of the issues I have currently is the inability to have someone in the back. Itís too cold to relax for any lengthy flight.

    In short. I canít stay out of the plane all winter and the girlfriend freezes solid after an hour.


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  22. #22

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    You can run a scat hose from the front heat to the back seat. My cub floor heat runs only to the back seat. I dress warm with bunny boots in the winter so I don't really need front heat. I do have separate defrost if needed to keep the front clear of frost. Lots of ways to fix your system just think about it and with a good IA it won't cost that much.
    DENNY
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  23. #23
    Charlie Longley's Avatar
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    Quote Originally Posted by twl View Post
    Is that Sutton on a 235? It’s very much different from my current setup with the muffler forward of the carb.


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    It’s a 320

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    Not sure if it is an option but on my c-90 pa11 I have another shroud on both sides that go around the exhaust from the Y to the exhaust has a 90* in it and that will double your heat recovery area and also pick up heat before you lose it to the air. -14* outside now so I'm not going to get a picture of it but maybe Glenn will post a pic when he gets back from flying .

  25. #25
    Little_Cub's Avatar
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    Take it to Arizona!


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    You might want to contact the current owner of 3788M and ask him for pix of his system. If is still the way I built it, it goes from the cold air inlet to a warm air exhaust on one side of the muffler divider to an inlet on the other side of the divider and then out of a now very hot air exhaust into the cabin.

    In short, I had the air circle the muffler twice before going into the cabin.

    It worked great for me, but be careful not to put anything in front of the cabin heater--the air is hot enough to melt a battery.
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  28. #28
    charlie husky's Avatar
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    $40-80.00 used Cessna 172 carb heat box stack heat robber, Wentworth aircraft KMIC. $37.00 2&1/2 inch y-tube from Aircraft. Spruce, plus scat tubing. Wye into existing cabin heat box, or run to another cabin heat box. =Lots moreClick image for larger version. 

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ID:	34499 heat. Add 12v 0.2amp computer heat sink muffin fan if you need more flow. .....or heated seats for $25-50.00. Minor alterations, log book entry by your IA supervising you. (Per the Mpls,Mn fsdo)

  29. #29

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    Quote Originally Posted by Paul Heinrich View Post
    You might want to contact the current owner of 3788M and ask him for pix of his system. If is still the way I built it, it goes from the cold air inlet to a warm air exhaust on one side of the muffler divider to an inlet on the other side of the divider and then out of a now very hot air exhaust into the cabin.

    In short, I had the air circle the muffler twice before going into the cabin.

    It worked great for me, but be careful not to put anything in front of the cabin heater--the air is hot enough to melt a battery.
    Paul, was this on an O-235?


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  30. #30

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    No, it was a 320, but with the original muffler and shroud so it should work just as well on the 235.
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  31. #31
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    An old trick Atlee used to tell us was to simply take copper or stainless "Brillo Pads" and pull them out so they will fit into the space between the outside of muffler and inside of the shroud. That will create considerable more potential heat than just rushing cold air over the hot muffler. However that reduces flow, so on some systems you need to run another hose from another inlet source to bring flow back up. It definitely creates more heat but can't speak to legalitys nowadays likely
    something the gov wouldn't want you to do. Likely a $3000 exhaust would be the legal path vs $3 worth of stainless wire?
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  32. #32

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    Quote Originally Posted by PerryB View Post
    Stewart, the left side of that system is carb heat. There is a baffle around the middle of the muffler and that heat shroud assy. is effectively split into two separate systems. The cabin heat supply is from the right front baffle, post#3/pic.#2.
    Is this actually the case and therefore do both halves of the heat shroud need ram air? I'm guessing one ram air source is from the top rear baffle (on the right side in my PA-12) and the other is from one of the 2 lower cowling intakes? Does it matter which ram air source powers the carb heat and cabin air sides?
    Every day's a school day

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