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Air box pressure differential

in 912 / 914 Technical Questions 7 years ago
Has anyone installed an UMA air box pressure differential gauge on a 914 engine? If so how did you hook it up. The documentation from UMA is kind of sparse.

  • Re: Air box pressure differential

    by » 7 years ago

    I have a 912iS. Same sort of issue.
    I added a Barbed fitting to the air box to sample its pressure for the Fuel pressure measurement.

    If you want to go this route do NOT drill it on the plane.
    You must be sure to collect and remove every minute drill chip.

    The easier solution is to tap into the small hose between the Fuel Pressure Regulator and the Airbox with a TEE Fitting.

    UMA is just selling a Generic Differential Pressure Gauge.
    They have no idea what you are going to measure with it so the instructions must be universal.

    What are YOU trying to measure?

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report

  • Re: Air box pressure differential

    by » 7 years ago

    The fuel/air box pressure differential. I don't know whether to take the fuel pressure from the pumps or after the fuel pressure regulator
      
    Report

  • Re: Air box pressure differential

    by » 7 years ago

    See Understanding the 914.

    You are measuring the (Differential) pressure that is seen at the Carburetors.
    You want to measure the difference in the Fuel Pressure AFTER the Regulator in relation to the AirBox Pressure.

    The High pressure (Wet) side of the UMA gauge will be tapped into the OUTPUT Hose of the Fuel Pressure regulator.
    The Differential Pressure(Dry) side of the UMA Gauge will be tapped into the small hose between the Airbox and the Fuel pressure regulator.

    The pressure Before the regulator is going to vary with Boost Pressure, Altitude, etc.
    The measured Fuel Pressure should remain steady at ~3.5psi Above the Airbox Pressure as the throttle changes.

    If you were to place a mechanical gauge in the fuel line you would see the Gauge (Not Differential) Pressure vary from a slight suction to 10 psi while the Differential Pressure remained at 3.5psi.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report
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