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Thread: Long High angle climbs

  1. #21
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    Quote Originally Posted by Dan L View Post
    Troy, it took me a while to run a test like yours. Last Friday I was loaded heavy for a camping trip and had about 3/4 fuel. I climbed at WOT and full rich from 2500’ to 7500’ at 70 mph. My fuel flow started at 13.3 gph and as I gained altitude dropped to about 12.8 gph. It ran smooth the entire climb. RPMs were 2500 with the Catto 84x42.5 prop.

    I have the Avstar carburetor and the CC sump kit installed.

    Thanks for doing that Dan,

    Fuel flows match, when it got rough FF was at about 12.5. Above that it was good.

    I went out Saturday and tried the same test, it did not do it that day. It was a much warmer day. I will keep investigating. I am talking with Cubcrafters so hopefully we get a answer over time.

  2. #22
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    Figured I would give an update to this. The issue was running to rich. If I lean just a touch at full throttle it stays smooth. The mixture leans slightly when you back off the throttle so that was why that fixed it.

    I had done this test and peak egt is not a very large spread. I really expected the spreads to be much higher at full throttle but they are not. I think this just because of the shortened induction system of the 340 and it is what you get. Full throttle to backed off are totally different numbers. The factory had said that some just need to be leaned and some don't.

    Tested at 7000ft

    63% power not WOT

    Egt Full Rich Peak Spread
    1 1175 1365 190
    2 1090 1385 295
    3 1395 1295 -100 was at peak at full rich
    4 1255 1285 30

    FF 11.1 6.7

    74% Power WOT

    Egt Full Rich Peak Spread
    1 1360 1390 30
    2 1120 1415 295
    3 1395 1440 45
    4 1105 1310 205

    FF 12.5 8.3

  3. #23
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    Default Re: Long High angle climbs

    Can you describe your roughness in more specific terms? Thanks..



    Quote Originally Posted by TroyBranch View Post
    Figured I would give an update to this. The issue was running to rich. If I lean just a touch at full throttle it stays smooth. The mixture leans slightly when you back off the throttle so that was why that fixed it.

    I had done this test and peak egt is not a very large spread. I really expected the spreads to be much higher at full throttle but they are not. I think this just because of the shortened induction system of the 340 and it is what you get. Full throttle to backed off are totally different numbers. The factory had said that some just need to be leaned and some don't.

    Tested at 7000ft

    63% power not WOT

    Egt Full Rich Peak Spread
    1 1175 1365 190
    2 1090 1385 295
    3 1395 1295 -100 was at peak at full rich
    4 1255 1285 30

    FF 11.1 6.7

    74% Power WOT

    Egt Full Rich Peak Spread
    1 1360 1390 30
    2 1120 1415 295
    3 1395 1440 45
    4 1105 1310 205

    FF 12.5 8.3

  4. #24
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    Quote Originally Posted by stretch View Post
    Can you describe your roughness in more specific terms? Thanks..
    At full rich going through 6000ft from say 4000ft at full power the engine would slowly become progressively less smooth to the point it would actually be misfiring, shuttering and sounding like it was going to quit. That would all stop immediately with throttle reduction. With it leaned slightly, this is all gone as well.

    Does that explain it better?

  5. #25
    Senior Member
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    Default Re: Long High angle climbs

    troy. Maybe totally unrelated but interesting……

    https://www.avweb.com/ownership/the-...t-and-leaning/

    307199DF-64E4-42E9-92E7-EE63B6A36744.jpg

    Quote Originally Posted by TroyBranch View Post
    At full rich going through 6000ft from say 4000ft at full power the engine would slowly become progressively less smooth to the point it would actually be misfiring, shuttering and sounding like it was going to quit. That would all stop immediately with throttle reduction. With it leaned slightly, this is all gone as well.

    Does that explain it better?
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

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