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Thread: Engine Cooling Fixes

  1. #1
    CamTom12's Avatar
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    Default Engine Cooling Fixes

    I've got a hot #3 (as high as +80 deg F) and higher oil temps than I'd like for most flights (220 deg F the other day while cruising at 2250-2300 rpm, 70 deg F ambient at 3,000 msl). Wasn't ever an issue until the plane came to the warmer temps of the lower 48.

    So right now I've got two SCAT tubes for cabin heat that run to individual heater muffs and then on to the valves mounted on the firewall. When closed these valves dump high pressure air below the baffling. I'm thinking about temporarily closing the tubes off on the baffle side to see if that helps cooling. Anyone see any issues with this? I was thinking that if it was successful I'd move the valves to the back of the baffle and just run the tubes straight into the firewall behind the valves. Any other ideas?

    Here's pics of the baffles where the tubes start and the firewall valves:





    I'm also going to go over the baffles with some rtv to make sure they're as sealed up as I can get them.

    I'm hoping the previous two mods will help oil temps. Otherwise I'm not sure what else I'd do. Here's the oil cooler installation:







    Another thing I'd like to try is to pressurize the intake side of the engine and see if I have any induction leaks on #3. Any other ideas?

  2. #2
    Clayton Harper's Avatar
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    Default Re: Engine Cooling Fixes

    The number one cylinder maybe getting more of the air on that side. Post some pictures. With the RV-6 cowl I suspect you have less air going though the total engine. Maybe Steve and Gilbert will look at the cooler position and say something different, but it looks very close to #4. The Dynofocal mount may make it hard to move it back. I do like the support tube off of the #4 cylinder for the oil cooler.
    The only true wisdom is in knowing you know nothing.
    Socrates

  3. #3
    tloes's Avatar
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    Default Re: Engine Cooling Fixes

    Is there any risk of damaging the muffler by not having the scat tubes feeding air to the heat exchanger? I thought that was why the heat control boxes were "diverters" instead of simple "open/closed" control.

    Best regards,

    Todd
    Todd Loes -- Waterloo, IA
    (PA22-150 N3568Z)

  4. #4
    Gilbert Pierce's Avatar
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    Default Re: Engine Cooling Fixes

    Quote Originally Posted by Clayton Harper View Post
    The number one cylinder maybe getting more of the air on that side. Post some pictures. With the RV-6 cowl I suspect you have less air going though the total engine. Maybe Steve and Gilbert will look at the cooler position and say something different, but it looks very close to #4. The Dynofocal mount may make it hard to move it back. I do like the support tube off of the #4 cylinder for the oil cooler.
    My oil cooler was originally mounted like that, standard RV6. I moved it back several inches thinking it would get less radiant heat from #4 cylinder head. No joy, it made no difference.

  5. #5
    Gilbert Pierce's Avatar
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    Default Re: Engine Cooling Fixes

    Do you have a lip on the bottom of the cowl to create a low pressure area at the bottom rear of the cowl?
    Attached Images Attached Images
    Last edited by Gilbert Pierce; 09-22-2015 at 09:35 AM.

  6. #6
    CamTom12's Avatar
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    Default Re: Engine Cooling Fixes

    Quote Originally Posted by Clayton Harper View Post
    The number one cylinder maybe getting more of the air on that side. Post some pictures. With the RV-6 cowl I suspect you have less air going though the total engine. Maybe Steve and Gilbert will look at the cooler position and say something different, but it looks very close to #4. The Dynofocal mount may make it hard to move it back. I do like the support tube off of the #4 cylinder for the oil cooler.
    Clayton,

    Roger built ramps into the baffling. It's hard to see in this pic but I can try to swing by the hangar this afternoon or tomorrow to get a better picture:




    Quote Originally Posted by tloes View Post
    Is there any risk of damaging the muffler by not having the scat tubes feeding air to the heat exchanger? I thought that was why the heat control boxes were "diverters" instead of simple "open/closed" control.

    Best regards,

    Todd
    You know, I'm not really sure. Just guessing, I can't imagine it would hurt the muff but maybe the SCAT tubing attached to it wouldn't last. Does anyone know?

  7. #7
    Gilbert Pierce's Avatar
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    Default Re: Engine Cooling Fixes

    I don't see where the air exits the bottom of the cowl. Look at the picture I posted above of the outlet.
    You need at least as much exit area if not more than inlet area.
    Last edited by Gilbert Pierce; 09-22-2015 at 09:35 AM.

  8. #8
    Homer Landreth's Avatar
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    Default Re: Engine Cooling Fixes

    Based on all your other activity not helping much, I think I would cast a critical eye on the brace you have crossing in front of the oil cooler. Since the air flow behind the brace would be deflected in a somewhat conical nature (and also considering turbulence) I would submit that there is a possibility of considerable airflow starvation to maybe a three to four inch lateral band of the oil cooler radiator. I understand the intention of the brace for additional support, but instead of crossing it in front of the oil cooler I would think that you could support the outboard portion of the Oil cooler and not be hugely sacrificing the desired additional support. With little or no risk of problems you could just take it off and make a couple of test hops to see if it is or is not a player in your temperature issues.

  9. #9
    CamTom12's Avatar
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    Default Re: Engine Cooling Fixes

    Quote Originally Posted by Gilbert Pierce View Post
    I don't see where the air exits the bottom of the cowl. Look at the picture I posted above of the outlet.
    You need at least as much exit area if not more than inlet area.
    The exit is hard to see in these pictures, but it does have an added lip (sheet metal tab) for scavenging:







    Quote Originally Posted by Homer Landreth View Post
    Based on all your other activity not helping much, I think I would cast a critical eye on the brace you have crossing in front of the oil cooler. Since the air flow behind the brace would be deflected in a somewhat conical nature (and also considering turbulence) I would submit that there is a possibility of considerable airflow starvation to maybe a three to four inch lateral band of the oil cooler radiator. I understand the intention of the brace for additional support, but instead of crossing it in front of the oil cooler I would think that you could support the outboard portion of the Oil cooler and not be hugely sacrificing the desired additional support. With little or no risk of problems you could just take it off and make a couple of test hops to see if it is or is not a player in your temperature issues.
    I'll keep the brace in mind. I haven't tried anything else yet though, so I'm going to try those other options and any other easy to effect changes suggested here before messing with structural bracing. In line with your thoughts, it might not be hard to add a fin running along the back of the bar in line with the flow to smooth the vortex street.

  10. #10
    CamTom12's Avatar
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    Default Re: Engine Cooling Fixes

    Quote Originally Posted by Gilbert Pierce View Post
    My oil cooler was originally mounted like that, standard RV6. I moved it back several inches thinking it would get less radiant heat from #4 cylinder head. No joy, it made no difference.
    Good to know! (sorry, I missed this post earlier)

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