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

    Have any of you tried continuous high angle climbs, like 70mph indicated for long periods of time less than half fuel solo?

    My usual routine would be climb hard and I found that after a minute or so in the climb the engine would not be quite as smooth so I just pulled the throttle a touch. That always fixed it. I figured it was just the modified carb set up on the 340 that was causing that. Pulling mixture did not help and just rose EGTs to a level that I would not except.

    Yesterday I figured I would leave the throttle in and see what happened. Full rich and continuous climb I would start to see a slight decay in fuel flow from high 12's to low 12's and roughness would start. (Flying above 5000ft) Drop the noes a touch, it would stop, pull the throttle a touch it would stop. Level flight it would flow over 13gph and smooth the whole time.

    Two people on board, full throttle smooth the entire time in the climb as I just cant get those really high climb angles.

    I think it is a combination of two things, the carb does not like the high angle attitude as the float is not doing a proper job and with lower fuel in the wing, it cannot provide enough head pressure for the fuel demand. I did a flow test before first flight but I know I could never set the plane up as high as angle it can do solo. Who new it could climb so steep

    Have anyone else tried this? Just wondering if I should be hunting for an underlying issue.

    Thanks

  2. #2
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    Default Re: Long High angle climbs

    How long is a 'long period of time' in your climb. I climb hard at times but I wouldn't guess for more than a minute or two.

    I usually fly frequently and can try to duplicate your observations.

    What carb do you have on your plane?
    Dan Arnold
    KEUL

  3. #3
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    I would say a minute or two as well. With my 1/4 tanks on the last flight when I tested it only took about 60 sec to start getting less smooth climbing at 70. Once passing through 6000ft from a 3500ft take off it got rough, pull the throttle a touch and dropped the nose a touch and smooth again. I plan to review the logs when I get time. I just filled it up and I will try the same thing with full fuel, I don't recall an issue with full fuel as I could not climb at such a steep angle.

    The engine was shipped in 2016. The engines before had a carb that would just not run smooth at full throttle I thought. I think they made changes to the design to solve that. I was told that before I started building so my memory has no detail of it.

  4. #4
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    Default Re: Long High angle climbs

    I believe you are correct in regards to the carb issues on earlier models.

    I recieved my motor in late 2018 and it has the Avstar -4PA carb. Which tanks do you have; extended or standard?

    I'll probably fly tomorrow but I have half fuel on board.
    Last edited by aeroaddict; 05-26-2020 at 09:30 AM.
    Dan Arnold
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  5. #5
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    Yes Dave I did read the article. I agree that pulling the throttle to keep it smooth is a solution but the fact that roughness becomes stumbling if the throttle is left full on is a concern. I don't think any plane should perform that way. I was just hoping more than one person on this forum could try it and comment on performing a 3 minute plus solo climb at 70mph. If more would try this I could at least find out if I am a one of or that some see the issue and some don't. I was very thankful of aeroaddict for taking the time to try it on his plane. It would be nice if others tried it as well.

  6. #6
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    Default Re: Long High angle climbs

    Yes, I agree it shouldn't do that for sure. I'm just thinking it might be the explanation. It's all about airflow. Lots of work goes into any good engine building getting the intake to flow the most efficiently and evenly to all the cylinders (as you know I'm sure). The intake on the new CC363i engines are superb (carbon fiber special design that really flows well).

    When we used to race alot, our engine builders played a huge amount with intake airflows and it can make a tremendous different in performance.

    So it just seems that perhaps when it's needing max power, your particular engine, carb, intake combination just isn't the most efficient and that minor throttle adjustment changes the plate and airflow into the carb making it more efficient. I don't know anything about those carbs but perhaps there is an adjustment that can/should be made?

    Just guess here but the fact that the problem clears up when the throttle is slightly retarded seems to be pointing to the problem??? Airflow....

    Maybe Andrew or someone at CC could jump on with their opinions? If I had a 340 any more, I'd sure go give it a try.

    Quote Originally Posted by TroyBranch View Post
    Yes Dave I did read the article. I agree that pulling the throttle to keep it smooth is a solution but the fact that roughness becomes stumbling if the throttle is left full on is a concern. I don't think any plane should perform that way. I was just hoping more than one person on this forum could try it and comment on performing a 3 minute plus solo climb at 70mph. If more would try this I could at least find out if I am a one of or that some see the issue and some don't. I was very thankful of aeroaddict for taking the time to try it on his plane. It would be nice if others tried it as well.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  7. #7
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    I do agree with you Dave, we talked to Marvel and there is nothing that can be done different to the carb unfortunately. When I down load the engine data, the CHT and EGTs are moving all over when full throttle is applied. Air fuel mixture seems to be quite bad.

    Quote Originally Posted by Daveembry View Post
    Yes, I agree it shouldn't do that for sure. I'm just thinking it might be the explanation. It's all about airflow. Lots of work goes into any good engine building getting the intake to flow the most efficiently and evenly to all the cylinders (as you know I'm sure). The intake on the new CC363i engines are superb (carbon fiber special design that really flows well).

    When we used to race alot, our engine builders played a huge amount with intake airflows and it can make a tremendous different in performance.

    So it just seems that perhaps when it's needing max power, your particular engine, carb, intake combination just isn't the most efficient and that minor throttle adjustment changes the plate and airflow into the carb making it more efficient. I don't know anything about those carbs but perhaps there is an adjustment that can/should be made?

    Just guess here but the fact that the problem clears up when the throttle is slightly retarded seems to be pointing to the problem??? Airflow....

    Maybe Andrew or someone at CC could jump on with their opinions? If I had a 340 any more, I'd sure go give it a try.

  8. #8
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    Default Re: Long High angle climbs

    Troy,

    Check out this Mike Busch article. I remembered reading it years ago where he talks about partially shutting the throttle. Specifically, itís on page 3 (ironically on the same page as a Cubcrafters ad! Haha)

    https://resources.savvyaviation.com/...ugh-engine.pdf

    Quote Originally Posted by TroyBranch View Post
    I would say a minute or two as well. With my 1/4 tanks on the last flight when I tested it only took about 60 sec to start getting less smooth climbing at 70. Once passing through 6000ft from a 3500ft take off it got rough, pull the throttle a touch and dropped the nose a touch and smooth again. I plan to review the logs when I get time. I just filled it up and I will try the same thing with full fuel, I don't recall an issue with full fuel as I could not climb at such a steep angle.

    The engine was shipped in 2016. The engines before had a carb that would just not run smooth at full throttle I thought. I think they made changes to the design to solve that. I was told that before I started building so my memory has no detail of it.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  9. #9
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    Default Re: Long High angle climbs

    Interesting, thanks. Next time I fly, I'll climb the plane like a home sick angel and see what happens.
    Dan Arnold
    KEUL

  10. #10
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    Default Re: Long High angle climbs

    Flew this morning.

    OAT 60F, 1/3 fuel, DA 2300, climbed 68mph, full rich at WOT for 2 mins. No issues, no loss or degradation in power. EGT/CHT all within limits.
    Dan Arnold
    KEUL

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