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75% power???

in General Tech Discussion 6 years ago

  • Re: 75% power???

    by » 6 years ago

    Is running your engine between 5000 -5500 RPM in cruise - actual recommendation from Rotax, or we just made this conclusion based on our experience in this country?. Can I see it in writing somewhere in any kind of documents?.
      
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  • Re: 75% power???

    by » 6 years ago

    5000 to 5500 is the best place because of vibration caused by the different length of the intake manifold between front and back cylinders. But since you installed the larger balance tube you can run at a lower speed without the vibration. Although I believe you should cruise at least 5000 because it is at the top of the torque curve for efficiency. Thats the way it was explained in a Rotax heavy maintenance class by Eric Tucker a factory expert.

    http://ctflier.com/topic/3016-in-heavy-maintenance-class-with-eric-tucker-as-instructor/
    Thank you said by: Eugene Klimenko,
      
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  • Re: 75% power???

    by » 6 years ago

    Is running your engine between 5000 -5500 RPM in cruise - an actual recommendation from Rotax, or we just made this conclusion based on our experience in this country?. Can I see it in writing somewhere in any kind of documents?.


    I think the chart you posted says it all.

    Take-Off Performance = 5800 rpm and Restricted to 5 minutes.
    Cruise Power = 5500rpm or less and is Permitted without Restriction.
    For Economic Reasons ($$$) Lower Power Settings can be used.

    Keep in mind that the chart is for a Variable Pitch Prop and serves to remind you to monitor your MAP at reduced RPMs.
    Do not OverPitch the Prop or the engine's life will be reduced.
    The Manifold pressures on a Fixed Pitch prop usually stays within the limits naturally.

    5000rpm (75%hp) to 5500rpm (Max Continuous Power) sounds like a reasonable recommendation unless you have a specific reason to select a lower power setting.

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

    Thank you said by: Eugene Klimenko
      
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  • Re: 75% power???

    by » 6 years ago

    Please also have a quick look at SL-912-016R1, page 5. The chart tells us al lot about the frame our engines may be used in.
    Regards
    Peter
    Thank you said by: Bill Hertzel, Eugene Klimenko
      
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  • Re: 75% power???

    by » 6 years ago

    Please also have a quick look at SL-912-016R1, page 5. The chart tells us al lot about the frame our engines may be used in.
    Regards
    Peter


    From this chart it seems the max MAP for take off (5800RPM) should be 27.5, the max. Continous Power is at 5500 and 27MAP, however the text says you can ignore the MAP settings above 5200 RPM. This is a bit confusing.

    I was also wondering about the following; let's say you follow the Rotax manual 5000RPM, 26MAP = 75% power / 18 L/h fuel flow. What if you want to maintain the same fuel flow on 3000ft or 5000ft, can you calculate your MAP setting to achive this?
    Screenshot2019-02-13at20.42.04_2019-02-13.png (You do not have access to download this file.)
      
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