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Starting 912is with EFIS on

in 912iS Technical Questions 8 years ago

  • Re: Starting 912is with EFIS on

    by » 8 years ago

    Are you using the newly approved filter announced by rotax? When I built my aircraft I installed a 10 micron filter which had a small
    surface area. As the filter would collect crud the pressure would decrease (due to the location of the sender in the system). I knew
    of another A/C that would have pressure readings in the 20PSI range. THE KITFOX factory published a service letter requiring the use of the rotax recommended fuel filter which has a much larger surface area and has the sender in the system just before the final filter.
    By doing that any above normal pressure indicates a possible clogged filter. The new instalation also has the Rotax recommended filter
    bypass check valve.So it is possible the pressure swings are from filter problems.
      
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  • Re: Starting 912is with EFIS on

    by » 8 years ago

    Hi Guys,
    thanks good thoughts I will look into it more. I am using the factory recommended fuel filter and have no data to suggest that the area of that filter is any different. I change the filter at factory recommended times (100 hrs) and find no difference with a fresh filter.

    I suspect, but do not know for sure that my sensor is reading a little low and/or the pressure valve is a little low

    I will try and upload Michael Stocks article again, it was rejected as too big last time.
    FuelP_Troubleshooting_EMU912iS_evo.compressed.pdf (You do not have access to download this file.)
      
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  • Re: Starting 912is with EFIS on

    by » 8 years ago

    Hi again All

    I had a long discussion with an expert that is helping me finalise my fuel system, panel etc. He is a full bottle on engines and their operation and understands exactly how the fuel system (and pressures) should behave with this engine.

    To cut a long story short - apparently it is perfectly normal to see pressure readings in that lower range with lower engine speeds, as it has something to do with the fuel pressure always being 45psi above the MANIFOLD pressure, not the ambient pressure. Yet, the fuel pressure gauge measures 'absolute' pressure.

    I am still not 100% sure of the technical side of the explanation but it comes down to the fact that the fuel pressure is regulated at 45psi in relation to the manifold pressure (which obviously changes with different throttle settings) and the fuel pressure measurement is reading an absolute pressure. The difference is where the issue comes in and is perfectly normal - in fact, as Bruce has explained to me would be abnormal if it didn't happen!

    Hope I haven't confused the issue more, but it's definitely not an engine issue, nor a pressure gauge issue.

    Ian
      
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  • Re: Starting 912is with EFIS on

    by » 8 years ago

    Hi All re Fuel Pressure.

    I have just done some more testing.

    1) Fuel pressure as displayed varied from 37.9-44.5 PSI that is 7 PSI

    2) However Fuel pressure as referenced to MAP only varied from 45.0-45.5 PSI only 0.5 PSI

    My conclusion is that Michael Stock and you expert are both correct fuel pressure is referenced to MAP and there is no problem as it is very constant. However what is displayed in the cockpit leads you naturally to conclude that it is very variable.

    So no real problem just a "instrumentation issue".

    Thanks everyone for your input, it turns out that everyone was correct ! and now I know a lot more about my engine...always good

    Kind regards
      
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  • Re: Starting 912is with EFIS on

    by » 2 years ago

    Hello Richard, 

    Can I ask you how did you connect the wiring to the 5600? Did you use the can buss lines? If yes, they were connected directly to the efis or with some module in the middle?

     

    Thank you,

    Filipe 

      
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