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912uls Oil pressure vale change

in General Tech Discussion 8 years ago

  • Re: 912uls Oil pressure vale change

    by » 8 years ago

    Hi John,

    I've needed better glasses a few times myself. :cheer:

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

      
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  • Re: 912uls Oil pressure vale change

    by » 8 years ago

    Hi All

    After my 1st 100 hourly on a 912ULS I observed that the oil pressure appeared to flucuate more than it did before the service.
    Because I have a Dynon Skyview, every parameter is recorded about once per second since the engine was delivered, which enabled me to analyse what was happening. The flucuation appeared to vary with RPM, so all my comparsions were done at 26inch MAP and 4800 RPM.
    For the first 100hours or so, the mean pressure was 59psi with a standard deviation from mean of 1.3psi ( a measurement of how it varies) The highest difference between max and min was 14 psi.
    After the service, and after a clean of the connector to the oil pressure sensor (pn 456180), I observed an avergae of 60psi, a standard deviation from mean of 1.9psi and a highest difference between max and min of 13psi.
    In the cockpit, it appeared worse than this because the response time of the guage is a lot faster than the 1 sec sample rate of the skyview "blackbox"

    On discussion with the local distributor, Bert Flood, I replaced the ball bearing in the oil pressure relief valve with the mushroom style valve and went for a fly. The mean pressure was now 65psi ( not unexpected), the standard deviation from mean was now 1.3psi, the same as before the service and the maximum diffence between max and min was now 10psi !

    It appears this modification has brought the variation back to its pre-service value but I am at a loss to explain why after an oil and oil filter change it all of a sudden increased its variation.
    The oil sender was next on my list but I probably wont bother.

    Doug
      
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  • Re: 912uls Oil pressure vale change

    by » 8 years ago

    I prefer the mushrooms on style oil pressure regulator better than the ball bearing too. I bet I have installed 70-80 of those.

    Your oil pressure can fluctuate and that is normal. It can happen for several reasons. i.e. air in n the system after and oil change, the oil pressure regulator setup, your instruments, poor ground connections, engine temps, pressure sender going bad, and the old ball bearing and plug setup, ect...
    Engine rpm plays a part.
    A poor ground coupled with engine rpm can make a 20-30 psi swing. This one issue just needs all the grounds tightened.

    Most of these can all be fairly normal and isn't something to worry about.

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

      
    Report

  • Re: 912uls Oil pressure vale change

    by » 8 years ago

    Hi Roger,
    Is there an easy way to tell if a 912UL has the ball bearing valve or the mushroom type without taking it out to inspect?
    For example, Is the head of the valve different?
      
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  • Re: 912uls Oil pressure vale change

    by » 8 years ago

    Hi Ian,

    You can tell if it is the new style plug on the outside. The old plug screw head was flat and solid. The newer style plug screw is hollowed out in the center of the plug. The old style was gold colored and the new aluminum colored. As far as the ball bearing verses mushroom you would have to pull it out. It only take a couple of minutes and easy to do.

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

      
    Report
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