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Thread: Long High angle climbs

  1. #11
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    I finally had time to do another flow test. I parked the plane on a steep hill and got over 30GPH. I then inspected for induction leaks, none found.

    I did a flight test with full fuel and had the same issue.

    I am at a loss here. The marvel carb has the biggest jet it can have.

    I called the factory to see if any of their aircraft had this issue and got zero help.

    As long as I do not fly with aggressive climbs over a minute or 2 I am fine.

    Maybe this is all from the highly modified induction system that may just cause gremlins is some CC340 engines, I have no idea.

  2. #12
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    Default Re: Long High angle climbs

    Stupid question: since the engine needs an air & fuel mixture to run, is it something as simple as a dirty air cleaner (which I think would make it run rich) or something that sucks air at high rpm/engine loads?
    Dan Arnold
    KEUL

  3. #13
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    Default Re: Long High angle climbs

    Troy, did you read this? Moving the throttle plate back changes the air flow and increases the atomization. I donít know but when you say pulling the throttle back a bit makes it go away, that sounds like that is the only variable besides lessening the angle/load.....thus.......plausible? Better airflow and atomization ????

    Higher load and increased heat in the climb.

    Quote Originally Posted by Daveembry View Post
    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
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  4. #14
    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.

  5. #15
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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."..

  6. #16
    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.

  7. #17
    Senior Member TroyBranch's Avatar
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    Default Re: Long High angle climbs

    Here is when I did a series of climbs. One side of the engine even looks to get cooler (#2 and #4) when I go full rich and full throttle. Looks to me like the cylinder 1 and 3 are not getting near as much fuel as 2 and 4. This is likely what the issue is.

    EX2.jpg

  8. #18
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    Default Re: Long High angle climbs

    Not trying to promote Mike Busch or Savvy Aviation, but I really like all his stuff. You may know but as an attempt to gather as much info as they can, they offer there free upload and analysis of our engine data. They have done thousands of these. Check it out https://www.savvyaviation.com/free-stuff/

    Quote Originally Posted by TroyBranch View Post
    Here is when I did a series of climbs. One side of the engine even looks to get cooler (#2 and #4) when I go full rich and full throttle. Looks to me like the cylinder 1 and 3 are not getting near as much fuel as 2 and 4. This is likely what the issue is.

    EX2.jpg
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  9. #19
    Senior Member chipallen's Avatar
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    Default Re: Long High angle climbs

    I've been a Savvy Analysis client for years and have over 3,700 flights uploaded to their database!! They are really good at helping troubleshoot engine problems. Highly recommended!

    Chip Allen

    SWT Aviation, Inc.
    Cubcrafters Southeast Sales Center
    Marietta, GA

  10. #20
    Senior Member Dan L's Avatar
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    Default Re: Long High angle climbs

    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 2500í to 7500í 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.
    Flying Carbon Cub EX #11 since 2011

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