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Thread: Injection Timing. Question for Tuners

  1. #1
    Forum Member 1st year Apprentice
    Join Date
    Apr 2011

    Default Injection Timing. Question for Tuners

    Its been a long time since I have posted here.
    I'm calling out to all the tuners out there.
    My question is when is the best time to start / turn on and inject fuel?

    I'm well aware that fuel needs to be injected into an open intake valve on the intake stroke (yes, the intake can only be open on the intake stroke) however I would like some real opinions and feedback from those in the know on:-
    1) How far after the intake valves open (in degrees) should the injectors start delivering fuel?
    2) If there is a range of degrees that should be used so as not to run out of time. (my guess / experience is 20 - 40 degrees after the intake opens) In other words if the injector on time is longer than the valve openning, how is this managed.
    3) Are there any considerations for injector timing when using different fuel types etc.. (for instance E85 takes longer to burn and usually needs more fuel / potentially longer injector on time).
    4) Anything else to consider?
    5) Anyone have any real dyno results?

  2. #2
    Junior Member Backyard Mechanic jondee86's Avatar
    Join Date
    Dec 2008
    Wellington, NZ

    Default Re: Injection Timing. Question for Tuners

    The easiest option for setting injection timing is End of Injection (EOI) timing. Typically the EOI default setting will be a few degrees before the intake valve closes if injecting on an open valve. Then the Start of Injection (SOI) floats according to the injection pulse width. If the pulse width exceeds the valve open time injection will start while the intake valve is still closed.

    Every engine is different and if the engine runs high injector duty cycle the benefits of EOI may be negligible at high rpm/load. In which case the main benefit of EOI timing will be a smoother and more stable idle.

    Cheers... jondee86

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