Is Rotax 912 engine's ignition timing variable or fixed?

  • Re: Rotax 912

    by » 7 months ago


    With the exception of a wee bit of retard if you have an engine with (connected) "Soft Start".

    (From Bill Martin "The engine starts with the timing at TDC and after a few seconds changes to the standard BTDC setting.")

    Optimum engine RPM is around 5200 (range 4800-5600 ??).

    Few, if any standard aircraft engines have variable timing (past starting aids). Car/motorcycle engines do and this may be kept or not, when converted for aircraft use. 

    Just like your lawn mower, aircraft engines are designed to operate within a small RPM band. Operating outside the recommended engine speeds is likely to lead to a shorter engine life.

    Having a narrow engine speed range allows the designer to strive for minimum weight/best power : weight, optimum volumetric efficiency, cooling and long in-service life. 


  • Re: Rotax 912

    by » 7 months ago

    Without getting into too much,

    If you have the green striped labeled ignition modules they start with 4 degrees BTDC and after the engine starts goes immediately to 26 degrees BTDC.

    If you have the yellow striped "soft start" system then the engine starts with 3 degrees ATDC and then after start it stays there for 4-5 seconds and switches to 26 degrees BTDC.

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

    Thank you said by: RotaxOwner Admin

  • Re: Rotax 912

    by » 7 months ago

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