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Flickering Oil Pressure

in 912 / 914 Technical Questions 13 years ago

  • Re: Flickering Oil Pressure

    by » 13 years ago

    I installed the replacement VDO sensor today. Everything looks great Was running mostly in the 50-60
    range but no more spikes or low readings. It does not zero out when engine shut off but that might just be a calibration on my Flydat, When off reads 0.3
    Thanks!
      
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  • Re: Flickering Oil Pressure

    by » 13 years ago

    Don't worry about tenths of a psi. The sender can still be off right from the factory. Just worry about over all pressure and trends you see on the gauge.

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

      
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  • Re: Flickering Oil Pressure

    by » 13 years ago

    Just like to add my findings to the topic....I too have a problem with flickering oil pressure with my 912 ULS installed in a Tecnam. Oil pressure on start would be 5 bar, gradually reducing to 4 bar after 10 min warm up. Full throttle at T/O would see it reduce to about 2.5 bar on the gauge then increase to around 3-3.5 bar when the oil temperature rose to 90-100C. At cruise, it would fluctuate up and down between 2.5-3.5 bar.My engine is 6 years old and logged 200 hours.
    I noticed so far no one has connected a master oil pressure gauge to check if gauge/sender error??
    I did and found the master gauges needle was fluctuating the same as the needle on the instrument panel gauge.
    So I concluded it wasn't the sender or the gauge. Fitted a new spring, retainer and piston valve as per Rotax SB....found it better, but still suffering pressure fluctuation albeit not as pronounced.
    Has anyone fitted a master oil pressure gauge to cross check their gauge??
    I like the idea of moving the sender to the firewall to reduce the vibration effect.
    I'm no expert on Rotax, so would appreciate feedback from the more experienced guys..thanks
      
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  • Re: Flickering Oil Pressure

    by » 13 years ago

    Moving the oil pressure sender to the firewall is a good idea for many. It is easy to do. Just two fittings, some hose an Adel clamp for the firewall and some fire sleeve for the oil line. It takes no time at all.


    Oil pressure test setup:
    I use a mechanical test gauge often and it will cost you $25 to make. The fittings are 1/8" NPT 27 thread. Standard fittings from the hardware store. When you start the engine loosen the fitting down by the mechanical gauge and let the air bleed out until you get a little oil. It just takes a few seconds then tighten the fitting. Now when you run the engine you can see both gauges in an out of the cockpit and compare. It is an inexpensive test gauge for oil pressure. It will work for fuel pressure too, but you need a gauge that only goes to 10 psi for fuel.
    oilpressuretestgauge.jpg (You do not have access to download this file.)
    oilpressuretestsetup.jpg (You do not have access to download this file.)
    oilpressuretestteefittingwithsender.jpg (You do not have access to download this file.)
    oiltestfittinginoilpressureport1.jpg (You do not have access to download this file.)
    oiltestfittinginoilpressuresendingport.jpg (You do not have access to download this file.)

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

      
    Report

  • Re: Flickering Oil Pressure

    by » 13 years ago

    After reading this topic, I moved my sender to the firewall last week. The fluctuation was somewhat better but still there. Mine is not so much a serious fluctuation as it is just bouncing around a normal average. It has done it since day one so I've just gotten used to it. I installed a small metering orifice in the hose barb thinking this would help smooth out the pressure fluctuations. It didn't. I have no doubt that moving the sensor to a remote location will extend its lifespan, so the modification was worthwhile even if it didn't cure the bouncing.

    Bill.
      
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