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Thread: CC340 running rich

  1. #1
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    Default CC340 running rich

    I know these engines tend to run rich. Sometimes inducing coughing/stumbling at full power, full rich. As expected, leaning resolves this. Pre-2014ish versions were improved via the carb sump insert and perforated fuel nozzle. My 2010, #122, was a great example of coughing before these mods and smooth running after.

    2014ish models and beyond had that stuff built in as standard. However, my 2014, #307, still produces that coughing that is only helped via leaning. Switching from the Marvel carb to an Avstar seems to have helped some, but not completely.

    What experience have others had? How sensitive to temperatures and altitude?

    Thanks!

    Andrew

  2. #2
    Senior Member TroyBranch's Avatar
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    Default Re: CC340 running rich

    I have a 2016 EX2. No coughing at full power. If I lean at full power EGT's ramp up as expected so I don't. EGTs are high even at full rich and full power. Full rich for me at full power all the time. Unless I am really high in alt. No change from +30c to -20c. I only lean below 65% power for the most part.

  3. #3
    Senior Member N867SP's Avatar
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    Default Re: CC340 running rich

    I have a 2014 EX with the mods, I lean on every flight. Typically cruise at 2200rpm or less. No issues at 180hrs


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    Pete
    ✈️CCK-1865-0078 N9PW
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  4. #4
    Senior Member randylervold's Avatar
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    Default Re: CC340 running rich

    As you guys have noticed there is simply individual aircraft variability. You'd think that with the same engine with the same car and same jetting they would be identical, but each aircraft ends up being a bit different.
    Randy Lervold

  5. #5
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    Default Re: CC340 running rich

    That's a good point Randy and something I've learned through this. In some ways that's a bit of the Cub heritage carrying on.

    I'm just trying to learn from those that have an engine/carb that acts like mine. What scenarios do they see it? How do they best manage it? Do CHT temps become an issue not being able to cool them with full rich? How much of a 'window' do they have between coughing from too rich and coughing from too lean?

    I DO like to lean on every flight. Like everyone else, looking for best power and fuel economy. Just have another variable to manage now.

    Andrew



    Quote Originally Posted by randylervold View Post
    As you guys have noticed there is simply individual aircraft variability. You'd think that with the same engine with the same car and same jetting they would be identical, but each aircraft ends up being a bit different.

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