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912UL 80 hp carb needle setting.

in 912 / 914 Technical Questions 13 years ago

  • Re: 912UL 80 hp carb needle setting.

    by » 13 years ago

    Roger,

    912 engines are getting more and more popular in powered parachutes these days. These guys can't choose a cruise RPM. They are pretty much locked in to whatever RPM gives them a fixed altitude and that is usually in the low 4000 RPMs. Outside of an in flight adjustable prop, what can they do to make the best of a low rpm situation?

    Bill.
      
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  • Re: 912UL 80 hp carb needle setting.

    by » 13 years ago

    Hi Bill,

    Unfortunately those guys are stuck. It probably wasn't the best match up for products, but there wasn't anything they could do. The 912UL 80 hp would be the better choice between the two engines. The prop idea would seem to make the most sense. I'm not sure if they are allowed an in flight adjustable prop? This is a little out of my knowledge base, maybe someone that owns one here on the forum will chime in.

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

      
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  • Re: 912UL 80 hp carb needle setting.

    by » 13 years ago

    Roger,

    I've now done two flights one at 5,200 & today at 5,ooo rpm. The ground settable Warp drive two blader prop. on my Rans S6-116 is set to the recommended min. of 5200 wot on climb out after take-off, [we are 260 ft above sea level here].
    Today measuring with dip stick before and after 56 minutes she used 15 litres. Not too scientific but equates to 16 L/h at 5000, however the Rotax book propeller power curve suggests 14 1/2. Today blanking the oil cooler and 75% of the water radiator yielded 112 F oil, still a lowish 170F water.

    Looking at the Heavy maint. Manual for 2.72 needle info. they show 3rd groove from the top, though the illustration is actually two down ! Plus a note this can be altered according to specific fuel consumption. So not really telling us one setting 'or else'.
    Mind you, whilst it's cold 5 C here I'm not changing anything.
    Now for their recommended operating RPMs, my book offers 5,500 max continuous, but also recommends 55% 4,300; 65% 4,400 & 75% 5,000 rpm. So though I don't doubt your own experience it seems Rotax are equable about slower regimes too. I put this here so anyone who's worried that they don't push so hard shouldn't think they are out of order, it's a versatile power plant by the look of it.

    mike hallam
      
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  • Re: 912UL 80 hp carb needle setting.

    by » 13 years ago

    Hello Mike
    From my experience the addition of a bypass thermostat in your coolant system would help considerably. Last winter I tried tape and home-built shutters on my Vixen 912UL and always had trouble regulating water/oil temps, especially in colder temps. A few months ago I installed a "Thermo-Bob" thermostat and now the warm-up times are shorter, temps constant at 180F (water) and 220F+ (oil). I tape the oil cooler for winter. I believe it was one of the better additions I have made.
    I also change the needles one notch from winter summer.
    Good luck with it.
    Don
      
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  • Re: 912UL 80 hp carb needle setting.

    by » 13 years ago

    Hi Mike,

    Remember that the book is written for a 5800 rpm WOT settings and included in that is in flight adjustable props. Your Warp is only ground adjustable. You can set your Warp for 5200 rpm, but WOT will be over the 5800 max. You will have a great climb prop and maybe with that Warp loosing a little climb performance at the setting too, plus it will be terrible for cruise. You need to balance your flight performance with the ground adjustable prop. The percentages are just that. It doesn't say fly at those settings. They are numbers for your reference based on 5800 rpm. You can move the needle clip up or down one, but you should have some decent gauges including an EGT and know how cold dry air verses warm wet or dry air affect the burn. Cold dry air makes leaner mixtures. As a rule one clip movement up or down is about 80F+/- EGT, but could be more under certain circumstances.
    A thermostat can make getting to 180F easier, but most thermostats stop at 180F. Limiting airflow across the engine and radiators can help too.

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

      
    Report
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