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Manifold pressure with jakes

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by bruce25, Aug 18, 2017.

  1. Aug 18, 2017 #1
    bruce25

    bruce25 Light Load Member

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    Apr 16, 2014
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    Whats a good manifold pressure with jakes on? For 12.7 pre egr i get around 10-14 psi seems low as uphill i get 27-30

    And yes jakes are not holding good i had them rebuild did not change selenoids everhead done two weeks ago. They are batter then before but still weak
     
    Last edited: Aug 18, 2017
    bruce25, Aug 18, 2017
    bruce25, Aug 18, 2017
    #1
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  3. Aug 18, 2017 #2
    ClineER

    ClineER Light Load Member

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    If memory serves correct that's normal. Boost is more a side product of the Jake's, not a particular number your shooting for
     
    ClineER, Aug 18, 2017
    ClineER, Aug 18, 2017
    #2
  4. Aug 18, 2017 #3
    bruce25

    bruce25 Light Load Member

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    Man not sure where to start would new selenoids improve braking performance? Over time they got weaker and weaker i though rebuilding them and overhead would do the trick but it only made little difference.
     
    bruce25, Aug 18, 2017
    bruce25, Aug 18, 2017
    #3
  5. Aug 19, 2017 #4
    swaan

    swaan Road Train Member

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    Depends on what model Jake heads you have.
    I have a 2000 14L ddec4 pre egr and can see 24psi on the Jake. Yours sounds a little low.

    I have a 2ws cat that sees 24-25 psi on the Jake also.

    I know the newest model of Jake head was about 2002 year engine for your 12.7.
    If your still running the old 3 peice Jake heads then it's probley normal..
    The new 2 peice are better.

    I know my Detroit Jake is ungodly loud with a nasty rap to it.. but works good.
     
    swaan, Aug 19, 2017
    swaan, Aug 19, 2017
    #4
    KB3MMX and Heavyd Thank this.
  7. Sep 2, 2017 #5
    Junkyard Johnney

    Junkyard Johnney Light Load Member

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    May 27, 2012
    Plains,Mt
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    DDec3, 14lbs boost on the low side, my highs go as much as 22lbs depending on outside air temp. Air flow is everything, restricted air filter can have an effect on that, same with exhaust. Turbo spool up is affected by air in and out. The older DDecs did not have a bunch of boost on jakes but it can be better than that. I also run Leon programming , that changed the whole world.
    J-J
     
    Junkyard Johnney, Sep 2, 2017
    Junkyard Johnney, Sep 2, 2017
    #5
  8. Sep 2, 2017 #6
    swaan

    swaan Road Train Member

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    BC canada
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    Programming may change the whole world on the way it runs but has 0 effect on Jake performance.
     
    swaan, Sep 2, 2017
    swaan, Sep 2, 2017
    #6
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