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Hi All

I have now been flying my Sling 2 with Garmin G3X and Rotax 912iS Sport for around 60 hours. All going well, however I do have a question about fuel usage.

My actual fuel usage is (on average 10% higher than what the Garmin is displaying. And the G3X only gets its data directly from the Rotax computers and totalises the data sent.

I have - on 5 separate occasions - taken from the G3X Touch the fuel usage number. I have then refilled the tanks from a calibrated source. On every occasion, actual fuel used is higher than the Garmin has indicated - between 6% and 12%, with the average around 10%.

Has anyone has had similar observations? Is there any way to rectify this? (The Garmin will not let you change 'K' values or the like with data supplied by the Rotax - you get what you get).

I have emailed the Garmin Team to see what they say, but right now the fuel flow is around 10% higher than what is indicated on my fuel-flow indicated by the Garmin.

Thanks
Ian

Has
  • Re: Fuel Burn Higher than Rotax Data

    by » 8 years ago


    Is this a Garmin problem ( indicated vs. actual) or is this an engine problem ( actual burn vs performance charts)?

    I think I've read somewhere that the ECU CAN bus fuel flow figure is quite accurate.

  • Re: Fuel Burn Higher than Rotax Data

    by » 8 years ago


    Hi Geoffrey

    That's a really good question and one that I was unsure of.

    So, I actually took the raw Garmin data (every piece of data output by second) and aggregated the data in Excel - it is pretty much exactly as the Garmin G3X Touch reports. Lower than the actual fuel usage.

    So, it appears to be an inaccuracy of the Rotax data.

    I sent an email to the Garmin guys and this is the response:

    **********************************************
    Good Morning,

    Yes, it looks like this information is coming from the FADEC system:



    I also agree that we don’t have a way for you to adjust the numbers coming from the FADEC system. So I will submit your feature request.

    Please let me know if you have any questions.
    garmin.jpg (You do not have access to download this file.)

  • Re: Fuel Burn Higher than Rotax Data

    by » 8 years ago


    ..and sorry, one point in response to your post Geoffrey - I think the problem is:

    "Actual Fuel Burn vs Reported Fuel Burn" - on the Rotax side of things.

  • Re: Fuel Burn Higher than Rotax Data

    by » 8 years ago


    Several sensors can be calibrated to be more accuarate by adjusting the "K" factor in the program. Some becomes a sensor type selection. Double check to see if either of these apply to you.

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


  • Re: Fuel Burn Higher than Rotax Data

    by » 8 years ago


    Hi Ian,
    I also have a 912IS and G3x reading the fuel flow data from the Rotax ECU. I have done 300+ hr and found it to be very accurate.

    Fisrt things would be to check whether you have a fuel leak somewhere or if you are loosing fuel in another way perhaps from the fuel caps , etc.

    Both Rotax and Garmin data should be very accurate and reliable, look at the instillation first

    Glenn

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