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"Air Pressure after Filter" on Man instrument readout

Discussion in 'Engines' started by CSkipR, Feb 25, 2020.

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  1. CSkipR

    CSkipR Member

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    New Smyrna Beach, Fl
    Air Pressure after Filter - At idle one engine reads 0 in WC and the other engine reads -1 in WC.

    What does this reading actually mean? What is better a minus number or 0?
  2. Capt Ralph

    Capt Ralph Senior Member

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    Air filter restriction. Better number; 0.

    If it reads -1 not running, just needs re-calibration.
    0 when not running, dirty or over oiled air filter.

    When running under load, you may see -1 or -2, this is normal.
    You have to have a lil low pressure for the CCV to draw correctly.

    Think info only and does not affect engine operation.
  3. Capt J

    Capt J Senior Member

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    On MAN's they generally run higher at cruise, depening on the engine. On the 1100 common rails, generally run 4-6 at cruise. I ran a set of 820 mans that were at 20, but someone recently painted the engines and I believe they got a bunch of overspray on the air filters. Best to get the numbers on your boat at cruise with clean filters as a baseline as hull vents can be restrictive and cause those numbers to be higher than normal but no fix for that.
  4. CSkipR

    CSkipR Member

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    Ok thanks. At 1850 rpm the port was -2 and the starboard -3 so all good.
  5. Capt Ralph

    Capt Ralph Senior Member

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    All is good.
    :)