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Fuel venting/dripping out air filter/intakes 912S

in General Tech Discussion 11 years ago

  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    Looks like the carb may have been flooding to a point. What I don't understand is that I have friends that fly out of those same elevations and fly at 9K'-13K' every week and they have never had the fuel come out. I do agree if you live and fly out of those elevations then a needle drop and or main jet change would certainly help. If you ever decide to fly on a trip down by sea level you'll have to keep a close eye on things.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    Do these high altitude 912S fly with an airbox? Yes or no.

    Second, what are the EGT at different altitudes, if we want to learn more and get smarter with altitude.
      
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  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    I admit a few have an airbox, but a few don't. I have set some of these up for people. I have done as you did and changed the factory jetting and needle position, but not because of fuel spitting, but just better EGT temps so it isn't quite so rich. I try and shoot for EGT temps between 1400F-1450F.

    The draw back in doing this of course is a big chance of too much leaning especially when one day you decide to fly in the lower altitudes. I guess this all boils down to what kind of flying you are going to do and where.

    If you never plan on going down to low altitudes then okay, but for the cross country guys that may fly down to sea level or above somewhat I wouldn't worry about getting it too lean. You need to consider all your flying when playing with jetting. If you fly at all kinds of altitudes then who cares if the EGT's are a little cool at times because it is a temporary state. I usually don't fly over 4500' and my EGT's are always around 1440F. There are occasions that I fly over mountains at 8k' to 10K'. The EGT's may drop to 1275F to 1350F, but it is usually a temporary state.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    I have found that engine RPM set to low will also cause this at carb tuning. With engine down at 800-900 rpm fuel will spill out of intakes.
      
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  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    If you really have this engine down around 800-900 rpm (which it should never be) then it will spit fuel. I'm surprised that the 912 series engine doesn't quit at 800-900 rpm. It vibrates too much and the floats are dancing all over in the bowls and they can't control the fuel level so it comes out the vent. A better idle point is 1650-1800 rpm. The lower 1650 rpm is better for a landing approach as the engine will not idle this low with wind coming through the prop. On the ground 1800 - 2000 is a better place to idle. At warm up 2100-2300 is a fair place to be while metals heat/expand and oil heats up to prevent unwanted vibration while sitting for these periods.

    A side note:

    Any thing that makes the 912 engine vibrate too much will cause the fuel to puke out the vent tubes because the carb floats are bouncing around too much.
    This can be caused by a bad carb sync, bad engine mounts, bad ignition, prop way out of balance, too low an rpm at idle, air leaks, bad ignition problem or any thing else that will cause excessive vibration.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report
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