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Im wondering - fuel pump and fmu?

Posted by 95'RS-T, May 19, 2009

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  1. 95'RS-T

    95'RS-T Proven Member

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    Germansville, Pennsylvania
    :rocks:I'm wondering if i should put a 190 fuel pump and a fmu in my 420a turbo? I'm running about 8psi on my stock internals and fuel system with no problems at all just a little turbo lag and i still do not have a problem with fuel cut or not enough fuel since i turbo-ed the car 3 months ago what do you guys think about this? i mean after i save up some money i wanna do a whole rebuild bottom and top end to see if i can make about 400hp with this thing.:hellyeah:
     

    378  0

    1995 Mitsubishi Eclipse GST
    · 2G DSM
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  2. rstare

    rstare Proven Member

    777
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    Joined Jun 9, 2008
    Winthrop Harbor, Illinois
    You can't run a turbo without on the stock fuel system. You need to more fuel, since your flowing more air.
     

    852  0

    1997 Mitsubishi Eclipse N/T
    manual · 2G DSM
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  3. 95'RS-T

    95'RS-T Proven Member

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    Joined Mar 10, 2009
    Germansville, Pennsylvania
    it seems to be working pretty fine for me i don't know if the owner before me put a different fuel pump in it or not but im running 8psi and it seems fine the wheels break loose and start spinning from first then i hit second and hit boost then they break loose again. the motor in my car i think was replaced with a 98 eclipse 420a
     

    378  0

    1995 Mitsubishi Eclipse GST
    · 2G DSM
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  4. Flipboi89

    Flipboi89 Proven Member

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    Joined Jul 30, 2008
    South burbs, Minnesota
    So you dont have a fmu? I have a 12:1 and a fuel pump and Im fine running 8 psi.
     
  5. 95'RS-T

    95'RS-T Proven Member

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    Joined Mar 10, 2009
    Germansville, Pennsylvania
    no i dont have either and im running fine i was wondering if i should get one?
     

    378  0

    1995 Mitsubishi Eclipse GST
    · 2G DSM
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  6. VelocitàPaola

    VelocitàPaola DSM N/T Moderator

    4,890
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    Joined Jun 14, 2005
    Ft. Lauderdale, Florida
    How do you know the car is running fine? Without a wideband oxygen sensor, you don't know much...

    At a bare minimum, you need a 12:1 FMU and a 255lph HP fuel pump -- otherwise, despite what it might feel like, I guarantee your car is not running "fine."
     

    1K  21

    1995 Mitsubishi Eclipse N/T
    manual · 2G DSM
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  7. cs82685

    cs82685 Proven Member

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    Joined Oct 29, 2004
    phillipsburg, New Jersey
    This, our you'll be doing that rebuild a lot sooner than you planned. BTW how much boost are you running?
     
  8. 95'RS-T

    95'RS-T Proven Member

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    Germansville, Pennsylvania
    im only running 8psi. what do you mean my car might not be running fine? I didn't ask this question to be flamed. I just wanted to know since im not having any problems should i get this stuff? I dont mean to be a dick either. I was just wondering.

    EDIT: im taking it down to my brother-in-law to hook it up to the snap on modis and i will let you all know good or bad.
     

    378  0

    1995 Mitsubishi Eclipse GST
    · 2G DSM
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  9. VelocitàPaola

    VelocitàPaola DSM N/T Moderator

    4,890
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    Joined Jun 14, 2005
    Ft. Lauderdale, Florida
    Don't worry, we're not here to flame you.

    Your ECU's fuel and ignition maps are not designed for forced induction. They only have data for naturally aspirated conditions. Thus, without an FMU or other means of adding fuel, there's no way of maintaining a stoichiometric air/fuel ratio.

    So, again, I ask the question: how do you know your car is running "fine?"

    Just feeling by the seat of your pants isn't a good method. Contrary to what you may think, neither is a narrowband oxygen sensor. You really need a wideband oxygen sensor.
     

    1K  21

    1995 Mitsubishi Eclipse N/T
    manual · 2G DSM
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  10. rstare

    rstare Proven Member

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    Winthrop Harbor, Illinois
    I would say chances are you're running lean and detonating really bad under boost.
     

    852  0

    1997 Mitsubishi Eclipse N/T
    manual · 2G DSM
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  11. 95'RS-T

    95'RS-T Proven Member

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    Germansville, Pennsylvania
    well if you mean by looking at a/f that im not sure about but, i did take it for a ride yesterday, and now when i smash the throttle it feels like i have a misfire but, if i slowly push the throttle in the boost climbs to about 8-9 psi with no problems such as bucking or missing and just takes right off. Also right now i dont have the money for the fuel pump and fmu so would i be alright to drive it without smashing the throttle and just try to stay out of boost? thanks for all your help im still kinda new to the tuning gig this is my first import all i really ever worked on was older carburetor v8s and i just got into sensors and things like that.

    EDIT: Would I be able to get away using a 190lph pump or do I need the 255lph?
     

    378  0

    1995 Mitsubishi Eclipse GST
    · 2G DSM
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  12. rstare

    rstare Proven Member

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    Winthrop Harbor, Illinois
    Out of boost you'll be just fine.
    The MAP sensor on our cars is a 1 bar sensor. Meaning it only reads up to atmospheric pressure. So, once you enter into boost, the ECU basically has no idea what's going on. (In the 96+ models it cuts fuel, you should be fine with a '95, however)
    When you enter boost the ECU will operate the injectors as if you were are at atmospheric pressure. This will not deliever enough fuel to reach a stoichiometric air/fuel ratio.
    The misfire you feel is because you're not getting enough fuel.
    You need the 12:1 fmu and a 255lph hp fuel pump.
     

    852  0

    1997 Mitsubishi Eclipse N/T
    manual · 2G DSM
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  13. rstare

    rstare Proven Member

    777
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    Joined Jun 9, 2008
    Winthrop Harbor, Illinois
    You need the 255lph, high pressure pump. The 12:1 fmu works by rasing the fuel pressure. The high pressure 255, is the only walbro pump that comes close to being able to supply enough fuel at those pressures.
     

    852  0

    1997 Mitsubishi Eclipse N/T
    manual · 2G DSM
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  14. 95'RS-T

    95'RS-T Proven Member

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    Germansville, Pennsylvania
    ok so your saying the 12:1 fmu will be good no matter what cause its raising the fuel pressure. and the 255 fuel pump will only come close to supplying with enough fuel is that because of the injectors? if i had bigger injectors the 255 would work excellent with 12:1 fmu with not having to worry about any thing correct?
     

    378  0

    1995 Mitsubishi Eclipse GST
    · 2G DSM
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  15. rstare

    rstare Proven Member

    777
    6
    Joined Jun 9, 2008
    Winthrop Harbor, Illinois
    The first statement is correct, the second is incorrect.
    Using the stock injectors, (which you have to do if you're using a 12:1 fmu) the 255lph high pressure pump is the only walbro pump that can supply enough fuel at the given pressures.
    The ECU doesn't recognize bigger injectors, so you would need a way to shorten the pulsewidths or lower the fuel pressure, otherwise you'll be running really rich at idle.
    If you get a 12:1 fmu and the Walbro 255lph hp pump, you'll be fine. This method has been run time and time again.
     

    852  0

    1997 Mitsubishi Eclipse N/T
    manual · 2G DSM
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  16. 95'RS-T

    95'RS-T Proven Member

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    Joined Mar 10, 2009
    Germansville, Pennsylvania
    ok thank you i got it now. :thumb:
     

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    1995 Mitsubishi Eclipse GST
    · 2G DSM
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  17. HadesOmega

    HadesOmega Proven Member

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    408, California
    Yeah you have to be running lean I have a Airtex inline pump on mine and when I turned it off and tried to boost it would build up boost and the AF ratio would go to rich and then plemmet into lean. Sorry an old post. Anyway if you say its running fine did you install your turbo kit yourself? How would you know you don't have any kind of fuel management?
     

    Street Build 2K  5

    1991 Mitsubishi Galant VR-4
    manual · Galant VR-4

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    1998 Mitsubishi Eclipse GST
    15.131 @ 95.580 · 2G DSM
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