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Thread: Overheating 180HP SC on amphib. Experimental

  1. #1
    barrie's Avatar
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    Overheating 180HP SC on amphib. Experimental

    Hi, I am attempting to solve an ongoing overheating problem for a friend. The engine baffles were not very good so we changed them with no measurable effect. His wide body(Smith)SC does not have a seaplane deflector lip on the lower cowl and we are considering installing one. Just don't have a design yet. He has high oil temps(220 and above) and excessive CHT's(400 + in cruise and never ending in climb). Has anyone any suggestions?
    Thanks
    Barrie

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    supercrow's Avatar
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    Don't know what other issues you may have, but I have brought oil temps down over 20 deg. in about 20 minutes by just temporarily riveting a lip (2" or so) on the bottom cowl and then went back and made a better fit after knowing it worked. Hope that helps; it almost certainly will make a difference. Also check air in and out of oil cooler and gill openings at the rear of side cowls. Getting heat out is more important than some may think, IMHO.
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  3. #3

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    Make sure the engine is getting enough fuel.
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    fobjob's Avatar
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    Go to Google and enter: site:supercub.org CHT and you will have a LOT of reading......
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    Hi guys, This aircraft is the second of two built by the same folks, this fellow has owned, and they both had the same excessive heat problems. This has been going on for a few years but the owner want's to put this to bed so he can enjoy his summer flying. Yes, the CHT issue is a lot of reading but the problem is with oil temps as well as all of the CHT's being high. I think supercrow is correct; we want to get rid of the heated low pressure air by the use of the lower cowl deflector for a start. Everything seems okay with the engine and all is setup in a proper SC configuration. I'm just hoping to find a solution that works. Has anyone used cowl flaps on a SC before?

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    wireweinie's Avatar
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    Start with the simple stuff. Inner baffles installed correctly between the cylinders? Are the outer baffles actually made for that cowling? Baffle seals installed and filling ALL gaps? Gaps sealed around a front mount oil cooler? Gap seals at the bottom of the front cowl ducts? Unless you can 100% verify that the baffling is correct, all the cowl flaps and seaplane lips won't cure the problem.

    Web
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  7. #7

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    Baffle rubber curves to the center so air can't blow out? Did you see the thread about gaps at the cowl doors? Maybe you need bigger gaps?
    Last edited by stewartb; 07-31-2019 at 06:52 PM.
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    Set up a water manometer with one end above the cylinders, and the other in the lower cowl with the water column in the cockpit. Mark the water level while at rest with the airplane level, then go fly and see if you have a pressure difference. I would think you would want somewhere around 2” difference in flight. Make adjustments on the cowl and baffles until you can get that. What type exhaust do you have? Is it blocking the air exit? Is it exiting through a hole forward that could be letting high pressure in the bottom? Do you have a forward oil cooler where the scoop could be letting high pressure air in the bottom? It’s all about pressure differential to get the flow!


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    Lycoming specifies 4” water pressure differential. If you only have two, that’s your problem.
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    skywagon8a's Avatar
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    Quote Originally Posted by barrie View Post
    ... Yes, the CHT issue is a lot of reading but the problem is with oil temps as well as all of the CHT's being high...
    Get the CHTs lower and the oil temperature will take care of itself.
    N1PA
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    Quote Originally Posted by fobjob View Post
    Lycoming specifies 4” water pressure differential. If you only have two, that’s your problem.
    Thanks, I didn’t have the spec handy.


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    barrie's Avatar
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    Okay, Looks like we have lots to go over. Thanks to all for the input. When this is under control I will try to post the results

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    DR-109's Avatar
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    Does anyone have drawings or dimensions for the seaplane lip?

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    Quote Originally Posted by DR-109 View Post
    Does anyone have drawings or dimensions for the seaplane lip?
    Heres an example,
    I’d go at least an inch wider,
    Click image for larger version. 

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    But as Stewart said, start by confirming you are getting enough fuel,
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  16. #16

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    Overheating 180HP SC on amphib. Experimental

    When I bought my Crosswinds short mount Charly gave me a fiberglass cooling lip. It was about 1-1/4 to 1-1/2" radius quarter round and I never used it. The Wildcat lower cowl has a 2-1/2" bend at approx 45* at the aft bottom cowl with hand formed end closures.

    Click image for larger version. 

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    Click image for larger version. 

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    behindpropellers's Avatar
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    Quote Originally Posted by barrie View Post
    Hi, I am attempting to solve an ongoing overheating problem for a friend. The engine baffles were not very good so we changed them with no measurable effect. His wide body(Smith)SC does not have a seaplane deflector lip on the lower cowl and we are considering installing one. Just don't have a design yet. He has high oil temps(220 and above) and excessive CHT's(400 + in cruise and never ending in climb). Has anyone any suggestions?
    Thanks
    Barrie
    Does this happen at full power full rich settings?

    Seems like it could also be a lean condition.

    I would check your mixture and throttle controls to make sure they are going to the stops.

    Tim

  18. #18

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    As discussed in the past, lots of little things add up to cooler temps;
    Sea plane lip, wider cowl doors, carb work, baffling ..
    another mod I tried, with very promising results, raise the entire cowling with relation to engine. Simple to do by removing lower rail fasteners on angle brackets near firewall. Tilt entire cowling up, clamp in place, and CAREFULLY check for clearance issues around nosebowl, oil cooler, ring gear, air box etc. if satisfied, drill new holes in rail corresponding with bracket.
    Obviously this will effect your baffling and should be checked.
    Every cub cowl fits differently, results may vary.

    if you can get the cowl inlets a 1/2 to 3/4 inch higher you’ve substantially increased volume of air coming in.
    (that’s not obstructed/deflecting off front cylinders)
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    skywagon8a's Avatar
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    Quote Originally Posted by barrie View Post
    Hi, I am attempting to solve an ongoing overheating problem for a friend. The engine baffles were not very good so we changed them with no measurable effect.
    Are you able to post pictures of the installation? This will help as there just may be something very obvious.
    N1PA

  20. #20
    barrie's Avatar
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    I won't be near the aircraft for a week or so and will try to get some pics then.

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    BC12D-4-85's Avatar
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    It may have been mentioned but Atlee Dodge used to sell a fiberglass lip for Cubs. Maybe that form mold is still around? I had one on a couple of floatplanes and they helped.

    Gary
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  22. #22
    C-FIJK's Avatar
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    Hi there where is the oil cooler located and also what engine is insatlled please post pics , I once had the same problem and recocating the oil cooler to the nose of the cowling solved the problem
    Gerry Marcil

    Every day spent flying is a great day !

  23. #23
    fobjob's Avatar
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    Google: site:supercub.org CHT

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    Hi Gerry, It's a Mattituck 0-360 not sure of the designation. The cooler is presently on the baffle behind #4 and we are holding off moving it as a last resort. I am quite sure it would make a considerable improvement. I will post pics after I can get back to the aircraft.
    Thanks
    Barrie

  25. #25

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    Quote Originally Posted by barrie View Post
    Hi Gerry, It's a Mattituck 0-360 not sure of the designation. The cooler is presently on the baffle behind #4 and we are holding off moving it as a last resort. I am quite sure it would make a considerable improvement. I will post pics after I can get back to the aircraft.
    Thanks
    Barrie
    Meh. Lots of us have/have had rear baffle mounted coolers. They’ve been used successfully for a long time.
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  26. #26
    C-FIJK's Avatar
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    Quote Originally Posted by stewartb View Post
    Meh. Lots of us have/have had rear baffle mounted coolers. They’ve been used successfully for a long time.
    I built a sportsman 2+2 and had cooling problems , the one thing that worked for me was moving the oil cooler up front and that made a huge difference and fix the problem , just speaking from my experience .
    Gerry Marcil

    Every day spent flying is a great day !
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  27. #27
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    I had a baffle-mounted oil cooler and had to move mine as well. Huge improvement. I haven't seen oil temps over 160 degrees F without blocking the inlet.

    However, if you have the room to alter your baffle mount so that the oil cooler angles back, I'd be willing to bet you'd see a significant improvement.

    Another potential fix, which would be easier to fab, would be a small deflector. It would sandwich between the head and the baffles, and would need to be long enough that it can go all the way down below the oil cooler opening in the baffle. I built one when I moved my oil cooler to help ensure my #4 cylinder fins weren't being robbed of airflow. If you had a deflector like that, any stand-off in the oil cooler mount to the baffle would create a little plenum that would help feed the oil cooler fins.

    Here's a link to some pictures of my fix where you can see the top part of the baffle: https://www.supercub.org/forum/showt...l=1#post739404

    My explanation of why I think it would help: https://www.supercub.org/forum/showt...l=1#post741624
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