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Thread: Lean AFR after injector swap

  1. #1
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    Default Lean AFR after injector swap

    I just put in a set of 79# injectors, and all i changed was the injector flow rate to match the injectors and the afr is real lean, 14:1, should be 9.8:1 and it idles real strange kinda like the lope from a big cam. I tried reducing B4307 with no change, I can correct it with A0008 at 1.25. But i would think i should not have to use this to correct it, just looking for some thoughts on this. Here are two of the logs, the first log is uncorrected the second is corrected with A0008 at 1.25. the idle increased as well with the correction which tells me there may be a vacume? leak but i didn't find one.
    Attached Files Attached Files
    2002 ws6 stock short block
    GMPP cnc LS6 Heads 11.4:1 cr
    .576 i .581 e 116 lobe
    D1SC @ 10#
    723 rwhp 654 rwtq on E-85

  2. #2
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    injectors can achieve their full potential only when the rest of the fuel system is up to the task. what other supporting fuel mods you got in there?

  3. #3
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    I have an APS dual in tank fuel pump, Aeormotive fuel pressure regulator. Thats it though, the fuel rails i got with the kit wont fit the injectors so i can't use the two -6 supply lines either, just using the stock feed line with a Magna fuel filter in place of the stock one. I do how ever, have the fuel pressure kind of low at 45 psi.
    2002 ws6 stock short block
    GMPP cnc LS6 Heads 11.4:1 cr
    .576 i .581 e 116 lobe
    D1SC @ 10#
    723 rwhp 654 rwtq on E-85

  4. #4
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    is it always low or just on WOT? is your IFR table calculated for the 45psi or the stock 58?

  5. #5
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    I have not even taken it out of the garage yet, it has very little gas. I just installed everything over this last weekend. I was just checking to make sure everything is in working order and to adjust the regulator, but from the limited reving it stays dead on 45.83 psi. And yes, i used one of your excel spread sheets to calculate for 45 psi., then input that into the IFR table. I didn't want to set the fuel pressure too high because i could not get the 60#er's i had before the D1 and E-85, to work right. I haven't been able to figure out how to properly tune for large injectors yet, I thought it would easier if the pressure was lower. Also the regulator is not referenced too manifold vaccume, so it should be constant.
    2002 ws6 stock short block
    GMPP cnc LS6 Heads 11.4:1 cr
    .576 i .581 e 116 lobe
    D1SC @ 10#
    723 rwhp 654 rwtq on E-85

  6. #6
    Lifetime Member 5.7ute's Avatar
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    Quote Originally Posted by vatman02
    I have not even taken it out of the garage yet, it has very little gas. I just installed everything over this last weekend. I was just checking to make sure everything is in working order and to adjust the regulator, but from the limited reving it stays dead on 45.83 psi. And yes, i used one of your excel spread sheets to calculate for 45 psi., then input that into the IFR table. I didn't want to set the fuel pressure too high because i could not get the 60#er's i had before the D1 and E-85, to work right. I haven't been able to figure out how to properly tune for large injectors yet, I thought it would easier if the pressure was lower. Also the regulator is not referenced too manifold vaccume, so it should be constant.
    Not referenced to manifold pressure is a curve, referenced is a constant.

  7. #7
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    Quote Originally Posted by 5.7ute
    Not referenced to manifold pressure is a curve, referenced is a constant.
    Doesn't this only apply to the IFR table, not fuel pressure?
    2002 ws6 stock short block
    GMPP cnc LS6 Heads 11.4:1 cr
    .576 i .581 e 116 lobe
    D1SC @ 10#
    723 rwhp 654 rwtq on E-85

  8. #8
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    IFR table is a result of fuel pressure, so you change one you change the other.

  9. #9
    Joe (Moderator) joecar's Avatar
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    Fuel pressure:
    - unreferenced regulator -> fuel pressure stays constant
    - MAP-referenced regulator -> fuel pressure varies as MAP varies (MAP "assists" the spring inside the regulator)

    IFR:
    - unreferenced regulator -> sloped IFR tble
    - MAP-referenced regulator-> constant flat IFR table

  10. #10
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    Quote Originally Posted by joecar
    Fuel pressure:
    - unreferenced regulator -> fuel pressure stays constant
    - MAP-referenced regulator -> fuel pressure varies as MAP varies (MAP "assists" the spring inside the regulator)

    IFR:
    - unreferenced regulator -> sloped IFR tble
    - MAP-referenced regulator-> constant flat IFR table
    That's what I was thinking. I have a constant fuel pressure and a sloped IFR table. Any thought's on why I'm running so lean. I am going to try reverting the voltage offset table back to stock and see what it does.
    2002 ws6 stock short block
    GMPP cnc LS6 Heads 11.4:1 cr
    .576 i .581 e 116 lobe
    D1SC @ 10#
    723 rwhp 654 rwtq on E-85

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