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Rotax 912 and oil pressure differences

in General Tech Discussion 10 years ago
Hi.
I have following problem.
When I't turn engine on I can read 4BAR oil pressure (cold). When engine is warmed up (oil about 80-90*C) pressure drops to 2,7-3BAR on 2000rpm. When I add to 4500RPM pressure drop's to about 2,5BAR, when I move back to idle it's raising back to 2,9-3,5BAR.
It is normal? My friend has 912ULS and he have always between 3,5-4BAR.
My engine is 1995 and 850hrs and probably I have old style oil pressure regulator. It can be caused by this?
I don't see fluctuations (flydat) but sometimes when I back from 4500 to 17000rpm there are a little bit of fluctuation in idle for a few seconds.

  • Re: Rotax 912 and oil pressure differences

    by » 10 years ago

    Your bar oil pressure numbers look fairly normal.



    Cold first start of the day oil pressure usually is a little higher. My cold start oil pressure is 60 psi and when warn it is 50-52. Things that can cause oil pressure differences are old style oil pressure regulator, many times it is the sender and sometimes it can be a poor ground (earth) wire on the sender or the instrument. Usually if there is a poor ground wire the oil pressure may drop from let's say 50 psi to 25-30 psi when the throttle is advanced and then goes back up to 50 at idle. The pressure varies significantly with the throttle. Not just a few psi.

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

      
    Report

  • Re: Rotax 912 and oil pressure differences

    by » 10 years ago

    Hmm, I'm really sure my electric but I'll check for sure.
      
    Report

  • Re: Rotax 912 and oil pressure differences

    by » 10 years ago

    "Hmm, I'm really sure my electric but I'll check for sure."

    Like I said your numbers don't look bad. You may only need to put in the new style oil pressure regulator parts and just double check the grounds. The quick and easy way to check the ground is use a jumper wire from the sender and go right to a known good ground or the battery negative. Then start and look at the numbers. If the problem went away then you know what the cause is and it only takes a few minutes.

    I tell everyone when checking ground (earth) connections that they may feel hand tight, but be wrench loose. I always put a wrench on every ground (earth) connection nut and bolt.

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

      
    Report

  • Re: Rotax 912 and oil pressure differences

    by » 10 years ago

    Hi. I checked everything again and resistances and visual inspections are ok. I have two wire oil pressure sensor directly connected to Flydat. Probably ground can't disrupt reading.
    Anyway yesterday I had 3.0 BAR during flight and about 2,5-2,7 on descending at low rpm.
    I'll thing about new regulator when I'll make any service.
      
    Report

  • Re: Rotax 912 and oil pressure differences

    by » 10 years ago

    3 bar to 2.7 bar isn't something to worry about going from cruise to idle rpm. That's only 4.5 psi. That would be fairly normal. A little resistance in your wiring could cause that or a little irregularity in the sender..

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

      
    Report
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