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2G Slow acceleration while under boost load.

Posted by JeffGS-T97, Sep 9, 2020

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  1. JeffGS-T97

    JeffGS-T97 Supporting Member

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    I have recently ran into an issue with my acceleration being poor when the boost begins to build. There is no bucking or jarring that takes place just a very noticeable lack of acceleration. I have been running the boost around 1 bar while driving casually on the street. The ignition seems healthy and the plugs are brand new all NGK. Where the engine used to just rip when boost climbs it just seems to stay linear in power as the boost rises. I have done multiple boost leak tests and didn't find any noticeable leaks but the vacuum on the gauge isn't down where it used to be it is a bit off from usual at about 400 mmhg in comparison of 500 mmhg before my boost gauge is a metric greddy so sorry if this makes it harder to crunch the numbers. If anyone has any suggestions i would love to hear them thank you.
     

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    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  2. Jk's97DSM

    Jk's97DSM Proven Member

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    Is the gauge reading boost when you are accelerating? Did this start happening after the plugs?
     

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    1990 Mitsubishi Mirage EXE (SLO CSM)
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    1992 Eagle Talon TSi AWD
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  3. JeffGS-T97

    JeffGS-T97 Supporting Member

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    Yes the gauge reads boost, it hits 1 bar with no issues. The fuel pressure stays consistent around 43 to 44 lbs under load.
     

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    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  4. Dericsh

    Dericsh Supporting Member

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    I saw a photo yesterday of a flex pipe that had deteriorated into just a small opening on the inside for the exhaust to flow thru. Just a thought, have you checked out for any possibility of a restriction in the exhaust system?
     

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    1991 Mitsubishi Eclipse GST
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  5. jimsgsx

    jimsgsx Proven Member

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    Isnt fuel pressure supposed to rise w boost?
     

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  6. JeffGS-T97

    JeffGS-T97 Supporting Member

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    Boost pressure when added puts a load against fuel pressure in which fuel pressure to the injectors is lowered at a 1=1 ratio. For every pound of boost the FPR must compensate for each pound of boost charged to the cylinder to maintain the correct Air/Fuel ratio, too much boost and the sytem will experience a lean condition.
     

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    1997 Mitsubishi Eclipse GST
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  7. JeffGS-T97

    JeffGS-T97 Supporting Member

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    To be honest that is something i thought about but dismissed immediately which brought back up makes a lot of sense. I think later i will take off some of the exhaust and inspect it. Thank you.
     

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    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  8. pauleyman

    pauleyman DSM Wiseman

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    This is a problem. If you're running one bar boost pressure should be the static pressure of the fuel should be regulator plus 1 bar more at 1 bar of boost. If you're saying 43 psi at full boost I would start looking there. The car would have to be lean and pulling timing like crazy.
     

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  9. JeffGS-T97

    JeffGS-T97 Supporting Member

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    So is the base fuel pressure set too low?
     

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  10. JeffGS-T97

    JeffGS-T97 Supporting Member

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    You are right sir a 1 to 1 increase. Thank you.
     

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    1997 Mitsubishi Eclipse GST
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  11. JeffGS-T97

    JeffGS-T97 Supporting Member

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    Ok i got off work a little early so i decided to go home and drive it around a bit and monitored the fuel pressure gauge when i started getting into boost. The fuel pressure increases in unison with the boost pressure. Looking around a bit i found a hose clamp that had become stripped from over tightening right after the BOV. I replaced it and drove it around a bit then layed into the throttle. Everything seems to be back to normal. Thank you for answering the thread.
     

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  12. Dericsh

    Dericsh Supporting Member

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    thanks for updating us with your fix!
     

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  13. JeffGS-T97

    JeffGS-T97 Supporting Member

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    I do believe my cat is flowing poorly so you made a great suggestion it ran on the rich side when i bought it and until i worked out alot of the issues.
     

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    1997 Mitsubishi Eclipse GST
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  14. TK's9d2TSi

    TK's9d2TSi Supporting Member

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    Glad you figured it out. Blt blt bltROFL
     

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  15. JeffGS-T97

    JeffGS-T97 Supporting Member

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    Thanks brother I appreciate you always trying to help.
     

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  16. Jk's97DSM

    Jk's97DSM Proven Member

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    That’s where I was going. If your hitting full boost, it’s either pulling timing or the clutch is slipping. He might be able to hit 1 bar with a restricted exhaust but you’d have a noticeable feeling and it would sound weird.
     

    215  1

    1990 Mitsubishi Mirage EXE (SLO CSM)
    manual · Misc Vehicles

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    1992 Eagle Talon TSi AWD
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