Click for Burger Click for Glendinning Click for Westport Click for JetForums Click for Mag Bay

Man Engine Gauge "air pressure after filter" question

Discussion in 'Technical Discussion' started by CSkipR, Jul 4, 2019.

You need to be registered and signed in to view this content.
  1. CSkipR, Jul 4, 2019
    #1
    CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    965
    Location:
    New Smyrna Beach, Fl
    What does the "air pressure after filter" identify on my Man eng gauges. What should the normal reading be and what improves it or makes it worse? When at cruise mine is "0 " although some Mans have a higher number on their motors and some with a negative number.
  2. Capt Ralph, Jul 4, 2019
    #2
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,726
    Location:
    Satsuma, FL
    Combination purposes I think.
    Air filter restriction.
    Altitude air pressure.
    Alarm system between air in and boost pressure after turbo.
    Maybe more.

    I would think a large negative value is bad, like dirty air filters.
    I like Zero.
    I would think a positive number is either read in error (didn't see the minus sign) or the system needs zero calibration.

    However, the computer is in charge of all of these values. if it runs, nothing is broke.
    Go Fishing, it's pretty down there today and I've seen the fireworks in your hood. Have fun.

    ,ralph
  3. Capt J, Jul 4, 2019
    #3
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,434
    Location:
    Fort Lauderdale
    It's the sensor right after the air filter. It indicates a dirty air filter and when it's time to clean it, OR if there is another air flow restriction before the air filter, such as the engine room vents not being adequate...…..they usually run -2 to -4 on all of the MAN boats I've ever run. Occasionally these sensors do go bad (like every 10 years), OR someone got overzealous with the air filter oil and it ruined the sensor. Zero is perfect as you have zero restriction.
  4. BoulderGT3, Jul 5, 2019
    #4
    BoulderGT3

    BoulderGT3 Senior Member

    Joined:
    Jun 19, 2014
    Messages:
    168
    Location:
    Ftl
    It measures vacuum downstream of the air filter. A greater negative # equals a dirty air filter. IIRC it alarms at -1.5bar. Here's a pic of mine with freshly cleaned airseps.

    Attached Files:

    Last edited by a moderator: Jul 5, 2019