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Thread: Engine CHT Question

  1. #1

    Join Date
    Sep 2011
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    Engine CHT Question

    I have a lycoming O-360 A1A installed in a Thorp T-18. Recently I found an intake leak from a hole in the manifold tube and replaced it on my Number 3 cylinder. Funny thing is that before the leak, my CHT's were very stable and all cylinders were almost always the same or within just 2 or 3 degrees.

    Now when I climb out, my CHT's have about a 20 degree difference between the front cylinders and rear cylinders. In cruise flight, the CHT's are all within ~5 degrees if I keep the EGT at 1325. That seems kind of rich to me.

    Any suggestions or is this normal and I was just very lucky with my intake leak?

  2. #2
    Chad Jensen's Avatar
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    Getting CHT's that close on a carb'd engine is unusual, so I'd suspect a bit of luck with your intake leak. On my O-360-A1A RV, my climb out CHT's would be spread by 30-50 degrees typically, and in cruise they would run 15-20 degrees apart, using 1300 EGT temps. That was my best economy setting. Full engine monitoring can sometimes be a "bane of existence" type of thing...fantastic tool, but can make things seem suspicious that aren't necessarily so.
    Chad Jensen
    EAA #755575

  3. #3

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    Thanks Chad. That is kind of what I thought. I know you should see some variation and you are right about the engine monitors. With a single EGT on my old airplane, it was not never an issue. Out of sight, out of mind.....

    Carb'd engines will have some variation but I was not sure of range of normal.

    Those temperature differences are very hard on an engine and rob power.

  4. #4
    Jim Hann's Avatar
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    Quote Originally Posted by Chad Jensen View Post
    ... using 1300 EGT temps. ...
    Chad (and others),

    Did you read Mike Busch's comments about EGTs and specific numbers? He doesn't like them and I think he has some good reasons why. Peak is all that matters (and is the bad place to be). It was in SA earlier this year. I'd have to look for it though, I can't remember what month.

    Just something else to think about.

    Jim
    Jim Hann
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  5. #5
    Chad Jensen's Avatar
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    Sure did Jim...that is one of the best articles on EGT that I've ever read. I agree with him 100% too. 1300 is where my engine ran best in nearly all situations. I should have clarified that in my post. EGT's don't really mean much, but I was able to establish early in my test phase where peak typically was, always ran rough (carb'd engine). 1300 is nearly always where I arrived at best the best cruise setting. Seems like that article was May or June???
    Chad Jensen
    EAA #755575

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