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Fuel burn at 75% Rotax 912 & 914

in 912 / 914 Technical Questions 10 years ago

  • Re: Fuel burn at 75% Rotax 912 & 914

    by » 10 years ago

    Probably the problem is to high manifold pressure. It's like driving 30kph on 5th gear by car.
    Engine is overloaded then.
      
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  • Re: Fuel burn at 75% Rotax 912 & 914

    by » 10 years ago

    Because your engine should get to a certain rpm range to develope torque and HP to turn the prop in the air. Unless a prop was absolutely flat it is under a load. Reduce the rpm too far and like they said above it is like driving a car 10mph in 5th gear when it should be in first with higher rpm to develope torque and HP.
    Our engines were designed to run within a certain rpm range to get our 100 hp and keep its reliability. Running too low depending on the rpm can cause bad harmonics in the gearbox, add 11:1 compression pulsation to the harmonics and then run or in that proverbial 5th gear at 10 mph and that engine is getting stressed from more than one angle. To get our 100 hp rating and keep its reliability the engine needs to be run in a fairly specific range of settings and or rpms.

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

      
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  • Re: Fuel burn at 75% Rotax 912 & 914

    by » 10 years ago

    Friday we flew on a 470 NM trip and the fuel burn was 4.88 USG per hour.
    New plugs
    OAT 48-60*F @4500 MSL
    5250 RPM
    Three blade DUC prop pitched at 21.5*
    5-7 knot X-wind from the west the entire trip
    Maxed out at 1320 LBS at take off.
    One rest and top off stop at the half way mark, again leaving at 1320 LBS.

    Rich
      
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