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Thread: Low manifold pressure indication

  1. #1

    Low manifold pressure indication

    On my IO-540 the manifold pressure has never read over about 28 inches, except when the engine is off. Then it reads ambient pressure.

    Most other planes I've seen read closer to ambient pressure at full throttle.

    It's been this way since the engine was new. The engine seems to make good power based on fuel flow, temps, and performance, so I don't think it's a weak engine. RPM is fine.

    Idle is fine so I don't suspect a manifold leak, but maybe I'm missing something there.

    I take MP off the aft right cylinder primer port, which I think is the standard location.

    All I can think of is some kind of blockage but there's just not that much to go wrong between the filter and the primer port. I've checked everything I can think of.

    Any ideas?

  2. #2
    If it reads correct on the ground the sensor is reading correct, I suspect that Van's filter and intake is the real problem.

    What were the other planes? and how were you measuring them?

    I only get around 28 at 2700 RPM in my RV-10.

    I get 29.1 in my RV-4, same size filter 4/6 of the airflow.
    Rob Hickman
    Advanced Flight Systems Inc.

  3. #3
    Mine reads well below ambient pressure on the ground. It read correctly on my old D-10, but I haven't checked it in the air yet with the AFS.

  4. #4
    Seems to read low at anything other than very low RPM. I noticed that the top calibration point is way out of sync with the displayed sensor value when it should be fairly close, but I'm not sure the bottom calibration point is correct either, so what is the correct method to calibrate it? The manual says it shouldn't require calibration.

  5. #5
    btw - when I say low, I mean VERY low, not just a little bit off.

  6. #6
    I suspect that you have the high pressure turbo manifold sensor. I will get the numbers for you in the morning.
    Rob Hickman
    Advanced Flight Systems Inc.

  7. #7
    The D10 was set to sensor type 1, which is listed as Dynon P/N 100434-000. The only other setting besides the green/yellow/red ranges was position, which was set to left.

  8. #8
    I did a little more research and that part number is Ballenger SNSR-03066 / Delphi 12247571

  9. #9
    Change the sensor type in calibration to 41201 Turbo and try it.
    Rob Hickman
    Advanced Flight Systems Inc.

  10. #10
    Got caught up in some other things, but it's still not reading correctly on the ground or in the air. It's closer, but still off by quite a bit

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