I'm having issues with my engine temp which i think might be the cause of low static rpm and low maximum rpm.

So even with 10 minutes of preheating the engine before take off,the maximum oil temp i can read is somewhere between 50-60(OAT 30 degrees C). Also the CHT hangs around 60.Oil pressure in the middle of green arc.

Normally the past years static rpm readings were around 5400 to 5500,with same prop but now i sometimes get the 5300 and sometimes 5200! rarely it hits the 5400 rpm without takeoff roll.( I ve checked the pressure and temp which are at sea level at past years and im at sea level also with same situations) Even after takeoff and in flight i cant pass through 5400 rpm!

I check the manifold pressure during the max throttle and it is within the maximum limits of 39.9.

Here is a pictures of my gauges when it hits maximum heat!

BTW aircraft type is an MTO SPORT 2010 with 914 UL engine. Engine hour is 400h.

Im not a technician but before going to take the acft to maintenance i would like to have a clue about the situation. Cold engine and low rpm gives me clue about maybe a combustion problems? CARB parts and fuel pumps are at their 30s hour since new.

Also reading low rpm might be a different problem than cold engine maybe. I was thinking of throttle position sensor, might it be faulty? Or maybe bad mixture ratio?!


9516_1_MTO.jpg (You do not have access to download this file.)
  • Re: 914UL Low Oil Temp-CHT and RPM

    by » one year ago

    Max Oil Temp. 130 °C (266 °F)
    Min Oil Temp. 50 °C / 120 °F
    Normal Oil operating temperature approx. 90 to 110 °C (190 – 230 °F)

    Max CHT is. 135 °C (275 °F) (No minimum or normal range listed)

    Many factors can affect the RPM output of the engine (OAT, air density, throttle position, propeller pitch, air filter condition, etc.). It would be best to have a Rotax IRMT with Rotax 914 rating and experience to look at your engine and download the TCU to make sure it is set up properly, and you are reaching 100% throttle position.

    Oil and CHT temps would not play a factor in your RPM issue, especially at the temperatures you have listed.

  • Re: 914UL Low Oil Temp-CHT and RPM

    by » one year ago

    I also have a 914 MTO Sport.

    I have no problems with it, but it tends to run a bit cold.

    How about your turbo - is it working at all?

    If it doesn't, then you have only about 80 HP.

    I always let the turbo cool as prescribed, so I don't cook/crack the oil inside.

    I hope you can have it fixed - it's a fun machine with the 914.

  • Re: 914UL Low Oil Temp-CHT and RPM

    by » one year ago

    Turbo and MAP working pretty good. I think connecting it to computer will be the way to go. Actually i m not familiar with this temps. I have flown around 1000 hours on a rotax 912 ,never had this temps. Normally we don't takeoff except the oil temo is n green arc. Its a bit strange for me to not be able to take it in green arc on ground in 30c sea level in 10-15 minutes.i ve applied all the manufactures suggestion about warm up. But green arc never seen by me even after 1 hour of flight. I ve fixed my IVO Prop propellers pitch to the fine position mechanically and disconnected the electric pitch but still these RPMS  gives me low power. Air filter is new, MAP is in its max readings 39.9.Also during my tests temp 25-30 and general atmospheric Pressure 1013-1016. so technically no turbo issue as i assume.

    I don't know if i see that MAP readings at max value,can still the throttle postilion be faulty or turbo?


  • Re: 914UL Low Oil Temp-CHT and RPM

    by » one year ago


    You stated that the RPM drop was recent.  Is the low oil and CH temp also a new condition or has it always been like that?

    Manifold pressure represents the “potential” to produce power. The actual power produced at a particular manifold pressure is also dependent on the fuel mixture.  Typically more fuel equals more power, so a power drop is not normally associated with running rich.  But as you go lean (of peak) power will drop. When flying an aircraft with adjustable mixture you can see this happen, as you adjust past lean of peak the power drops and the EGT and CHT cool.  I’m curious if your EGT is also cooler on some or all cylinders. 

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