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Thread: leaning ops, manifold pressure, rpm?

  1. #1
    Senior Member Dan L's Avatar
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    Default leaning ops, manifold pressure, rpm?

    I have an Electronics International UBG16 in my Carbon Cub EX and have the CC O-340 engine. With the UBG16 I have fuel flow and manifold pressure modules. I'm wondering if anyone has developed a desired fuel flow rate for various RPM's and manifold pressures? For example (and this is just an unverified number) at 2400 RPM and 24" of manifold pressure a fuel flow of 8.0 gph would mean the engine is leaned correctly.

    I developed a chart like this using an EI UBG16 in a fuel injected engine with a constant speed prop and use it for leaning all of the time. This particular engine has GAMI injectors and I run lean-of-peak with it but the principle is the same other than the prop being a constant speed. This engine has been run about 1500 hours using this technique.

    Using manifold pressure takes care of altitude changes.

  2. #2
    Senior Member Dan L's Avatar
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    Default Re: leaning ops, manifold pressure, rpm?

    I downloaded the AFM from this site and found some of the information I was looking for on pages 106 and 107. The charts show fuel flow values for given manifold pressures and RPM's. But it just goes up to combinations that produce 80 hp maximum. With my EX I'm not limited to the 80 hp restriction that the LSA's are. So I understand why the charts stop at this point.

    I wonder if Aerosports could furnish figures for higher HP settings?

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    Default Re: leaning ops, manifold pressure, rpm?

    Wondering if anyone has any updates to the two postings below? I am interested in a simple leaning method like a rule of thumb, without a lot of memorising peak EGT's and stuff because the way I fly I might bang into something if I look down that much! Way I see it, this is a gorge exploring Cub, not a boring cruiser where you need something to do to while away the hours..... Paul.

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    Default Re: leaning ops, manifold pressure, rpm?

    It dosen't get any easier than leaning until it runs rough and then push in until it smooths out. Always worked for me.

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    Default Re: leaning ops, manifold pressure, rpm?

    Quote Originally Posted by tcwilliams View Post
    It dosen't get any easier than leaning until it runs rough and then push in until it smooths out. Always worked for me.
    Thanks tcwilliams, I will carry on doing that too. I guess I got a bit confused with discussions on egt methods and thought maybe I should do something more sophisticated, but really when it comes down to it I just want to be sure I'm not damaging the engine while getting good fuel economy (mainly so I can extend the range).
    Has anyone worked out whether that method provides LOP or ROP? In my AC I really could not be any leaner because the engine would quit, so does that mean it's LOP? Just curious. Paul.

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    Member jim plaster's Avatar
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    Default Re: leaning ops, manifold pressure, rpm?

    Be careful if you're a lean of peak guy....detonation can happen fast! My procedure for leaning has been slowly pull the mixture until things begin to run rough....then richen the mixture 100_125* egt cooler. The cost of fuel is cheaper than a top overhaul. If I'm less than 2000 ft I won't bother with leaning at all.

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    Default Re: leaning ops, manifold pressure, rpm?

    Quote Originally Posted by pwill435 View Post
    Thanks tcwilliams, I will carry on doing that too. I guess I got a bit confused with discussions on egt methods and thought maybe I should do something more sophisticated, but really when it comes down to it I just want to be sure I'm not damaging the engine while getting good fuel economy (mainly so I can extend the range).
    Has anyone worked out whether that method provides LOP or ROP? In my AC I really could not be any leaner because the engine would quit, so does that mean it's LOP? Just curious. Paul.

    Agree with the posts re how to lean as a rule of thumb and it works!.My first CC did not have any egt and I worried I was doing it right by simply pulling out the mixture till it runs rough noting a slight drop in RPM then push it back in until it runs smooth. So on my second CC I had an EGT and sure enough the cited method was spot on and I never had to consult the egt again. Since you are enriching the mixture by this method you would be ROP Rich of Peak. PS I don't think ( but others may know better) that you can really run a four cylinder LOP? As stated I think it just quits or runs too rough before getting there so LOP I think is for those with 6 cylinders? Best Gary
    Last edited by glickle; 12-24-2015 at 10:34 AM.

  8. #8
    Senior Member Cubrath's Avatar
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    Default Re: leaning ops, manifold pressure, rpm?

    It's not so much the number of cylinders that matters running LOP its the fuel delivery. It's hard to run a carbureted engine LOP with good results. If it was fuel injected with GAMI injectors it would be no problem.

  9. #9
    Senior Member Dan L's Avatar
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    Default Re: leaning ops, manifold pressure, rpm?

    Here's the chart I came up with albeit not complete. Perhaps with the FX and the EX and EX2 available now and not under the 80 hp rule CC could furnish additional data?

    CC O-340 180 HP
    Best Power Best Econ. Best Power Best Econ
    RPM M. P. % HP Gal/Hr Gal/Hr RPM M. P. % HP Gal/Hr Gal/Hr
    1900 10.6 22 2.8 2300 13.0 40 4.3
    11.0 26 3.1 13.6 42 4.3
    12.1 28 3.0 14.0 44 4.8
    12.3 30 3.2 18.8 5.5
    13.1 32 3.3 19.2 6.3
    17.3 4.1 20.0 57 8.3
    17.8 4.5 21.0 60 8.7
    18.3 4.5 22.0 63 9.1
    2000 11.2 26 3.2 23.0 66 9.6
    11.4 28 3.3 24.0 69 10.0
    12.1 30 3.1 25.0 73 10.6
    13.4 32 3.7 26.0 76 11.0
    13.9 34 4.0 2400 13.5 44 4.7
    16.2 4.1 18.9 5.6
    18.0 4.2 19.9 6.0
    18.8 4.9 20.6 7.1
    2100 11.7 31 3.7 20.0 60 8.5
    12.0 32 3.6 21.0 64 9.1
    13.0 35 4.2 22.0 66 9.4
    13.9 37 4.3 23.0 69 9.8
    14.2 39 4.3 24.0 73 10.4
    14.9 43 4.2 25.0 76 10.8
    17.8 5.2 2500 18.1 6.8
    18.0 4.8 18.5 6.7
    19.0 5.1 20.0 64 9.3 8.1
    2200 12.2 36 4.0 21.0 68 9.9 7.8
    12.9 37 4.0 22.0 71 10.3
    13.4 40 4.4 23.0 74 10.7
    14.2 43 4.6 2600 19.3 9.1
    15.1 44 4.7 20.0 8.2
    18.2 5.5 24.0 76 11.0
    18.8 5.7 20.0 69 10.6
    19.2 5.9 2700 21.0 71 10.9
    20.0 55 5.9 22.0 74 11.4
    21.0 57 8.4 23.0 77 11.9
    22.0 59 8.7 20.0 72 12.0
    23.0 62 9.2 21.0 75 12.5
    24.0 66 10.4
    25.0 70 10.4
    26.0 73 10.8
    27.0 75 11.1
    Flying Carbon Cub EX #11 since 2011

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    Default Re: leaning ops, manifold pressure, rpm?

    Still struggling to develop a simple chart for operating at 2000' AMSL above 80hp.

    Is anyone from CubCrafters following this thread?

    Ever hopeful,



    -- martin

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