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Oil pressure fluctuations

in 912 / 914 Technical Questions 6 years ago

  • Re: Oil pressure fluctuations

    by » 6 years ago

    The ultimate diagnostic is to temporarily replace the Oil Pressure sender with a mechanical gauge at the engine.
    If the mechanical gauge shows unexplained pressure variation, the problem is Not a sensor issue.
    This would mean that you really do have Varying Oil Pressure and changing sensors and gauges is just masking the problem by treating the symptoms.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report

  • Re: Oil pressure fluctuations

    by » 6 years ago

    The ultimate diagnostic is to temporarily replace the Oil Pressure sender with a mechanical gauge at the engine.
    If the mechanical gauge shows unexplained pressure variation, the problem is Not a sensor issue.
    This would mean that you really do have Varying Oil Pressure and changing sensors and gauges is just masking the problem by treating the symptoms.


    Agreed. We did basically that from the start with an independent sensor which transmits it's values via bluetooth. We then branched simultaneously parallel the Bluetooth-sensor and either the new Rotax or the Kavlico sensor to compare values side by side.

    I posted the results: no fluctuations with the bluetooth sensor, but with both the Rotax and the Kavlico-Sensor.
    The only refutation might be an unknown averaging or damping of the bluetooth sensor, but we don't have any indication for that.
      
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  • Re: Oil pressure fluctuations

    by » 6 years ago

    A Bluetooth Sender is an Electronic device! NOT Mechanical!
    You need an actual Mechanical gauge with a Bourdon Tube driving the needle on the face of the dial.
    Nothing electronic. You will need to be close to the engine to be able to read this type of gauge.
    A generic 0-100psi pressure gauge would do the job.
    This is only for temporary use so don't get carried away buying something fancy that you are not going to use for more than an hour

    Automotive variations have a few feet of very small Oil hose connecting the engine oil to the gauge allowing you to read it in the cockpit but it is still completely mechanical.
    Google "Bosch SP0F000044" for an example.
    They can be had for < $20 at your local auto parts store.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report

  • Re: Oil pressure fluctuations

    by » 6 years ago

    You hit the mark. With a mechanical gauge, we see fluctuations.
    They "look" like harmonic oscillations. That implies that the sample rate of all the systems we compared (Bluetooth sensor-phone; VDO sensor with Dynon and with analog instrument; kavlico and Rotax with the Dynon) is to slow to show the fast pressure changes. What we saw as "fluctuations" may in fact be an oscillation. We need an oscilloscope to check this.

    Any idea what might the reason?
    Obviously the pressure regulation valve. But the same symptoms with old oil pump housing, old spring and ball as well as with new housing, new spring, mushroom?
    The only old part is the rotor and he "looks" good...
      
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  • Re: Oil pressure fluctuations

    by » 6 years ago

    The reason is in the design of the Rotax regulator. It can "Oscillate"!

    Re-Read the 7th. post of this thread...
    https://www.rotax-owner.com/en/rotax-forum/3-4-stroke-technical-questions/6674-oil-pressure-fluctuations#19262

    Does your issue look similar to the videos in the 9th Post?

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report
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