1991 E36 325i Help with fuel injector sizes.

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  1. 1991 E36 325i Help with fuel injector sizes. 
    #1
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    DonutMan1's Car Details
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    Hey all

    Wonder if there is anyone outthere who can help with my fuel injectors. I'm in the process of doing a stroker conversion on my 1991 325. Increasing the displacement to 2.9 will mean an increase injectors will be necessary. i'm trying to use a fuel measurement chart but can't get to grips with it. Algebra is not my strong point. lol. I understand that at WOT my injectors are not to exceed 80 %, as this can put added presure on my fuel pump and can effect fuel presure and flow. Will my fuel pump need upgrading as well ??

    Cheers Donut
     
     

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    #2
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    I would of thought with a displacement increase and injector pressure increase you would need a modified or separate fuel management system including a uprated fuel pump anyway.

    Would love to know how this turns out looks like a pretty good upgrade.
     
     

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    #3
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    robrex's Car Details
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    B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour in yankee speak
    You can use injector formulas to calculate fuel requirements too

    HP x BSFC
    ------------------------------
    no of injectors x Duty cycle

    So assuming 80% duty cycle and 0.6 BSFC (always aim high/ not sure what they are for this engine)

    300 x 0.6
    --------------- = 37.5lb/hr
    6 x 0.80

    now times 37.5 by 10.5 to get cc and 393 basically means 400cc injectors are needed to flow 300bhp in you engine at 43psi fuel pressure.

    this is taken and slightly tweeked from a honda forums but sounds about right to me. im just not sure what the stock fuel pressure is on these engines? can anyone confirm ive done this correctly.
     
     

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    Ian S's Car Details
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    Are you sure it's necessary? From what I can remember the 3.0 US S50 M3 uses the same injectors as the M50?

    What information do you have so far?

    Ian
     
     

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    if this helps i know you can use 2.5 injectors in a 2.8 and there work fine with a m50 manifold, i would say 2.8 or 3.0 injectors should do the job i think
     
     

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    mistreku's Car Details
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    wouldn't you be able to fix this with an fuel pressure regulator with your stock injectors?
    There are only two products required to make the universe work properly: Duct tape and WD40. 


    If it moves (and it shouldn't): duct tape. 
If it doesn’t move (and it should): WD40.

    Everything else is just stuff.
     
     

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    #7
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    Thx ALL

    So info so far seems to collaborate with what you are all saying.

    1. Injector sizes are the same as US M3.

    2. The increase of displacement does not require and increase of injector size. (just yet . LoL ).

    3. Algebra is not my strong point. lol.

    4. Im sure i read somewhere if set up correctly Fuel regulators might be the way to go.

    All in all if i take out my injectors and get them cleaned (anyone know a good postal place ??) Look at replacing my old fuel pump with a new OEM , thing should be ok.


    Cheers for the help guys.
    Last edited by DonutMan1; 08-02-2010 at 10:33.
     
     

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