ROTAX 912 ULSFR Question,

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Dear fellow pilots,

i am flying evektor eurostar with 2 blade variable pitch prop and 100 HP rotax, my question (which i couldnt get any response from the manufacturer) is,
Although the MAPs are given ranging from 25.1 to 27.2 inches Hg( 0.84 atm to 0.91 atm) , the only range I could observe from Dynon is around 21 to 22 during cruising flight, neither prop pitch nor throttle could increase these values to the range given in the POH,

no rough engine, no lost power, everything seems to be quite normal during flight,
thanks in advance for your valuable opinions,

greetings from Turkey,

[BackPacker]

Sounds either like an induction system that's overly restrictive, or a calibration problem in the Dynon.

What is the MAP that the Dynon shows when the engine is not running? It should be ambient: 29.92 inches on an ISA day.

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i will check that on the weekend as soon as possible, thanks for the quick response

[Rod1]

Mu 912uls (100hp) is fine (SCS1 Controller). Do you have fuel flow? This is another method of measuring power.

Rod1

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Rod,
the procedure i follow immediately after take off is,increase prop pitch to ensure that rpm is slightly below 5500 rpm ( fuel flow is around 22 ltrs/h), then depending on my desired cruise speed i reduce the throttle to rpm range of 4800 to 5200, fuel flow at 5100 rpm is around 19 ltrs/h,
by the way the oil pressure is always either 2 or 2.1 (2 is the minimum of green arc),
thanks,

[gasax]

My 912ULS has a fixed pitch prop - but your fuel flows sound like they are in the right area. At 4900 it usually indicates 24.5 or thereabout.

Oil pressure sounds a little low - but I notice that the recommended Aerosport 4 has a lower viscosity and so I see 2.9 to 3 when hot as opposed to 3.5 to 3.8 with the earlier Shell VSX. This is with oil temperatures around75 to 90C.

[patowalker]

The 912ULSFR, which is no longer built, is a de-tuned 912ULS, so fuel burn will be different.

In 2009 Dynon released a batch of incorrect MAP sensors, identifiable by the label which reads p/n 12223861. The correct p/n is 12247571. Both are made by Delphi and Dynon replaced the incorrect ones FOC.

[Flap40]

The figures in the performance section of the Rotax Operators manual make no mention of any correction for altitude and temperature in relation to manifold pressure. There is a graph that shows the relationship between Power output (kw) and Density altitude.

Unless you fly everywhere at sea level on a standard day, you are unlikely to see the book figures. Manifold pressure decreases with altitude (unless you have a turbo/super charger).

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thank you Flap40 and all fellow pilots who have responded, now it is okay,
during summer time density altitude of the field is approximately 4000 ft which reduces 29.92 to around 26 inch Hg, now i solved the puzzle

[Mark 1]

Density altitude (the temperature effect) will not affect MP, although the air temperature will affect the power produced. At wide open throttle settings you should see an MP roughly corresponding to the ambient air pressure (PA not DA). It may be slightly higher or lower depending on the induction system. So full throttle is about 30"MP at sea level dropping to about 21" at 10,000' for a non-turbo engine.

21-22" MP isn't unusual for cruising flight at lower altitudes.

When you say MAPs are given ranging from 25.1 to 27.2 inches Hg; what is that for? If it's for power setting in the cruise, it seems rather high. It might make more sense if it's to do with take off power

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Mark, these figures are taken from poh cruise settings and varies with density altitude,

Thank you