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Hi. I found today that my oil pressure is about 4BAR on cold, 3bar on warm (60*C) and it's drops to about 2,2-2,5 bar on high rpm (I tested up to 4500RPM).
When I'm back on idle it rise to 2.8-3BAR.

What can be a reason of falling pressure on high rpm? Engine is not burning oil, I made new wires so connections should be fine. I will replace pressure sender but I' tested two of them.
  • Re: Oil pressure drops on high rpm

    by » 10 years ago


    Does the drop in pressure relate to an increase in temperature?

  • Re: Oil pressure drops on high rpm

    by » 10 years ago


    Pretty sure this is a poor ground. I have seen a couple dozen like this. The resistance changes as the rpm changes because things are grounded to the engine.

    All ground wires are considered hand tight and wrench loose until you put a wrench on them. Check the crimp connections too. If you crimped too much insulation and not enough bare wire or the wire is breaking and only hanging on by a strand or two that will cause the same thing.

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


  • Re: Oil pressure drops on high rpm

    by » 10 years ago


    hm, I'll check.

  • Re: Oil pressure drops on high rpm

    by » 10 years ago


    Hi Roger,

    Can you please explain in more detail why the resistance changes as RPM increase?
    I do not understand the relationship between a poor ground connection for the pressure sender unit and the engine RPM. I would have expected the wiring resistance is independant of the RPM.

    Also, from your experience of this problem of pressure drop on high RPM, is it related to a particular pressure sender model (Honeywell or other)?

    If the pressure drops for a minute or two after removing high RPM, is this still a grounding problem or any suggestions?
    For example, on a 912UL normal pressure warming up (3.0-4.0), after take off (1.9-2.0) for a minute or so, then back to normal (2.9 - 3.3) for the rest of the flight. Do you think this is likely grounding?

  • Re: Oil pressure drops on high rpm

    by » 10 years ago


    I found that these sensors are very sensitive for vibrations. My old sensor changes indication from 0 to 5 bar due to gently tapping it.

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