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goodings(at)yorku.ca
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 Posted: Mon Apr 19, 2010 7:37 am Post subject: Fuel consumption for the 912S |
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People have been quoting fuel consumption figures for the Rotax 914
recently. The figures quoted seem rather high. What fuel consumption do
people get with the Rotax 912S (100 HP)? We have measured it pretty
carefully over quite a number of hours, and we are getting slightly under
16 litres/hr (4.34 U.S. gal/hr) at 5200 RPM cruise. We use mainly 91
octane mogas without ethanol additive, but probably 1/3 of the fuel used
is 100 LL because we don't have a choice at many small airports in
Ontario. Here are other details of our aircraft, but I'm not sure they
are very relevant to fuel consumption. Our aircraft is a CH601HD with a
66-inch, 3-blade, GSC prop flying with 2 people (and 1 small Italian
greyhound!) near 1200 lbs gross weight. Because of that thick wing, our
cruise is only about 100-105 mph.
John Goodings, C-FGPJ, CH601HD with R912S, Carp/Ottawa/Toronto.
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Gilles.Thesee(at)ac-greno
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| Posted: Mon Apr 19, 2010 8:14 am Post subject: Fuel consumption for the 912S |
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John,
| Quote: |
People have been quoting fuel consumption figures for the Rotax 914
recently. The figures quoted seem rather high.
About 21 litre/h is quite normal for a 100 hp engine cruising at 75%, be
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it a Rotax, a Jabiru or a Lyco/Conti.
| Quote: | What fuel consumption do people get with the Rotax 912S (100 HP)? We
have measured it pretty carefully over quite a number of hours, and we
are getting slightly under 16 litres/hr (4.34 U.S. gal/hr) at 5200 RPM
cruise.
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16 L/h corresponds to about 60% power with a 100 hp.
Are you talking of *cruise* consumption, or overall consumption ? If you
are doing much circuit work, low numbers are normal, since you are most
of the time at part throttle.
Best regards,
--
Gilles
http://contrails.free.fr
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goodings(at)yorku.ca
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| Posted: Tue Apr 20, 2010 6:58 am Post subject: Fuel consumption for the 912S |
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Gilles:
My figure of 16 litres/hr (4.34 U.S. gal/hr) refers to takeoff at Carp
(near Ottawa), fly at 5200 RPM (about 80% power?) for 2 hours and land at
Orillia Lake St. John, and the reverse trip. The figure is lower when
many circuits are involved, as you suggest. In my experience, Conti/Lycos
(O-200A in particular) in C-150/C-152s were never as low as this in fuel
consumption.
John.
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Gilles.Thesee(at)ac-greno
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| Posted: Tue Apr 20, 2010 1:40 pm Post subject: Fuel consumption for the 912S |
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John Goodings a écrit :
| Quote: |
My figure of 16 litres/hr (4.34 U.S. gal/hr) refers to takeoff at Carp
(near Ottawa), fly at 5200 RPM (about 80% power?) for 2 hours and land
at Orillia Lake St. John, and the reverse trip. The figure is lower
when many circuits are involved, as you suggest. In my experience,
Conti/Lycos (O-200A in particular) in C-150/C-152s were never as low
as this in fuel consumption.
John,
|
To get an estimate of your power setting, RPM alone is not enough, you
need additional info, such as manifold pressure.
16 L/h is the 75% manufacturer number for the 912 (5000 rpm/27.2"). For
the 912S, Rotax gives a low 18,5 L/h (at) 5000rpm/26". But the planes I
flew burn something closer to 20 L/h with the 100 hp Rotax.
The 100 hp C-150 also burns about 21 L/h at 75 % power, as does our 914.
There is no mystery : if the mixture is correct, all engines burn about
the same fuel at the same power setting.
Best regards,
--
Gilles
http://contrails.free.fr
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rampil
Joined: 04 May 2007
Posts: 870
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| Posted: Wed Apr 21, 2010 4:06 am Post subject: Re: Fuel consumption for the 912S |
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Gentlemen,
Any rational discussion of fuel flow rate on the Rotax 912 +/- S really
requires specifying the altitude at which you are burning the fuel.
Twenty three inches and 5000 at 3000 MSL may be 4.6 gal/hr but at
9000' wot with MP=22.6" the FF may be over 7 gph
Cheers
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