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Thread: Looking for a fix- high CHTs on SQ2

  1. #41
    tedwaltman1's Avatar
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    Thank you for input on recent tests Doug. And your thoughts/experience much appreciated too Oliver.

    Std certified Cubs have cowl "cheeks." I'm thoughtfully optimistic that the cheeks I added to my SQ-2 did indeed make a difference. Another friend with an SQ-2, and same exact engine as mine, built a plenum inside his cowl. That interestingly enough did not make any difference at all for his cooling.
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  2. #42
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by tedwaltman1 View Post
    Thank you for input on recent tests Doug. And your thoughts/experience much appreciated too Oliver.

    Std certified Cubs have cowl "cheeks." I'm thoughtfully optimistic that the cheeks I added to my SQ-2 did indeed make a difference. Another friend with an SQ-2, and same exact engine as mine, built a plenum inside his cowl. That interestingly enough did not make any difference at all for his cooling.
    should be relatively easy to test closing off front center of cowling and just leaving maybe 8" at ends open.... maybe try a couple sizes of openings, or make it controllable with a cable from inside....

  3. #43
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by d_kandle View Post
    . I thought that adding some scoops on the top of the cowl would make a big difference, but they didn't.
    Attachment 50223

    Adding 14 sq. in. of frontal opening (with the two scoops) made no difference. That doesn't seem logical to me.
    Im thinking like the upper cowl like a bucket that is ALREADY FULL of water(air). Adding more(scoops) just spills more overboard..... and directs flow out front like the other post mentions....


    so blocking the center opening off to limit the inlet size/volume might be helpful or at least a good test.

  4. #44

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    Today I added a deflector just in front of the scoops which goes from the cowling (upper) down to the case and extends across about the middle 1/2 of the engine. That should force any air coming into the scoops aft and not allow much air to move forward near the center of the engine. As soon as our temps gets below 100 here I'll so some test flying.
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  5. #45

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    At this point I can say Oliver is correct. I added a dam on the upper cowling to block air going forward from the two scoops I had already put on top. It made a huge difference. I did the two sides slightly different (by mistake but I'll say it was on purpose). On the more complete covered side I got a 60 degree improvement. On the less covered side 30-40 degrees. Adding the scoops alone did nothing. But blocking the air from coming forward of the scoops seems to do the trick. The photograph is looking in the front over #2. I'll probably never know if the same thing could be achieved without the scoops as they are already there (better is the enemy of good enough).
    At this point I'll probably just clean things up a bit.
    Click image for larger version. 

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  6. #46
    www.SkupTech.com mike mcs repair's Avatar
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    Be interesting if someone will try blocking front middle off at cowl itself. just leaving openings outboard in high pressure area. Bet the effects will be same as your air dam. Thanks for reporting your results back.


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  7. #47
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by d_kandle View Post
    At this point I can say Oliver is correct. I added a dam on the upper cowling to block air going forward from the two scoops I had already put on top. It made a huge difference. I did the two sides slightly different (by mistake but I'll say it was on purpose). On the more complete covered side I got a 60 degree improvement. On the less covered side 30-40 degrees. Adding the scoops alone did nothing. But blocking the air from coming forward of the scoops seems to do the trick. The photograph is looking in the front over #2. I'll probably never know if the same thing could be achieved without the scoops as they are already there (better is the enemy of good enough).
    At this point I'll probably just clean things up a bit.
    Click image for larger version. 

Name:	CowlChange.jpg 
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    You could also do a quick test by taping over new scoops to block them off. I bet there will be no difference, as your dam is blocking the excess air up top from setting up a current flow and exiting front as easily.


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  8. #48
    tedwaltman1's Avatar
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    I’m assuming this picture is looking forward over the fins of #1? I’m trying to envision all the above text & pics and am confused.

  9. #49

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    Quote Originally Posted by tedwaltman1 View Post
    I’m assuming this picture is looking forward over the fins of #1? I’m trying to envision all the above text & pics and am confused.
    Looking in the front, left side - I think that should be #2.
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  10. #50

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    It would interesting to see if air is actually entering the top scoops. I would think that’s a low pressure area - at least lower pressure than what’s in the upper cowl from ram air . I had thought of placing scoops further outboard near baffle seals. It would be fun to tuft the upper cowl from edge to edge where you could see them from the pilot seat.
    Maybe no need for scoops at all, 60° is really significant! interesting progress you are making.
    thanks for keeping us in the loop.
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  11. #51

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    Quote Originally Posted by Oliver View Post
    It would interesting to see if air is actually entering the top scoops. I would think that’s a low pressure area - at least lower pressure than what’s in the upper cowl from ram air . I had thought of placing scoops further outboard near baffle seals. .
    The scoops are 1.5" high which is puts them well above the boundary layer. I'll likely take Mike's suggestion and tape them off to see what happens. I may also do the heavy black oil test where I put a drop of really thick black oil on something and see where the track ends up going.
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  12. #52
    www.SkupTech.com mike mcs repair's Avatar
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    Block all but outer 6”


    Click image for larger version. 

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