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Thread: LF4 engine converted to multiport FI from direct injection question

  1. #1
    Potential Tuner
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    Mar 2015
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    LF4 engine converted to multiport FI from direct injection question

    Hello, I am interested in converting an LF4 from direct injection to port fuel injection.

    My question is- are the DI injectors offset a certain degree crank rotation so they spray once the intake valve is closed?

    The thing I want to make sure I avoid is the port fuel injectors spraying fuel after the valve is closed, which would result in them spraying fuel on the back side of the closed intake valve.

  2. #2
    Yes, check table 33913 - Injector SOI Base. Here you can program the start of the injection angle (SOI) in crankshaft degrees BTDC.
    1998 Pontiac Grand Prix GTP (first 3800 FWD in the tens), 9.499 @ 145.13 mph
    1998 Pontiac Firebird (first 3800 RWD in the eights), 843 whp, 8.991 @ 152.12 mph, driven by Tim King
    1999 Pontiac Grand Prix GT (first 3800 FWD in the eights), 8.902 @ 154.90 mph, driven by Bob Cook
    2000 Pontiac Bonneville SSEi (first 3800 Bonneville in the twelves, elevens and tens), 10.711 @ 125.71 mph, driven by Ed Morad
    2008 Pontiac G8 (first G8 in the tens), 10.727 @ 129.87 mph
    2018 Cadillac ATS-V, 619 whp

  3. #3
    Potential Tuner
    Join Date
    Mar 2015
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    Awesome, thanks Mr. INTENSE!
    Last edited by KINGVEE; 10-15-2019 at 11:52 AM.