Thread: fuel injector timing changes due to non OEM camshaft

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  1. #1 fuel injector timing changes due to non OEM camshaft 
    GXP Level Member Turbocharged400sbc's Avatar
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    frankly since our ST1R cam isn't too far off of oem it shouldn't be much of an issue...however recently ive been working on an 85 mustank GT (with all 89 interior/wiring) that we recently got rid of the AFM PMS IV and went to the megasquirt MS3Pro (its the system that resulted from refinments of the eMSpro that they developed with Spectre.

    well injector timing makes huge differences, HUGE especially for idle quality esp with a big overlap cam (making sure to spray on an open intake valve AFTER the exhaust valve has closed, etc)

    this is really closely related to whether your going static with the injectors since the pcm has a hard limit on the end of the injection event

    so now im going to do some maths to see how far the st1r is from stock but id figure on seing whether any of ya have played with this.

    shooting for 750 at the wheels has me looking for every little gain I can find that we can test back to back on the dyno.

    /insanity
    ~James~ Psychotic Gearhead
    projects: 84 Cressida waGN~ 90 LN3 3800, equal length headers, T70, 89 700r4, misc parts,
    1994 Oldsmobile 442 (462ci-4wd-2 engines) L67/4t80e^2,
    00 Turbo Regal 608 fwhp 575ftlbs at 5500rpm, 98 WhippledRiv, 97 GTP
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  2. #2 Re: fuel injector timing changes due to non OEM camshaft 
    SE Level Member SlowFiero's Avatar
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    I played with it a bit, however our tables don't appear to match how it's calculated in LS pcms. With access to a scope to watch inj firing vs crank angle, you could play with the values and figure out how to move it and get the results your looking for.

    It does make a big difference in idle quality and even torque and hp if your injectors are big enough to keep pulse widths low. It will also help with exhaust smell and fuel mileage.
    Billet 6262 T3 turbo, PT1001 intercooler, ST1 cam, 140 springs, pushrods, N* TB, L26 upper, HV3, otherwise stock L32. 10.007 @ 135.54with 1.46 60' 3130 lbs

    Old GenV M90, XP, heads, N* TB, ST2 intercooler - 11.425@115.60 1.54 60'
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  3. #3 Re: fuel injector timing changes due to non OEM camshaft 
    GXP Level Member Turbocharged400sbc's Avatar
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    yeah, one thing is that it actually runs better with the 127lb injectors at idle than it did with the 90's

    with the MS3pro CAN bus allowing for a trans control GPIO and having native support for the 18x/3x C3I it makes me want to ditch the oem pcm

    the fact that two of em can communicate over the CAN bus has me wishing we could afford two of em for the 442
    ~James~ Psychotic Gearhead
    projects: 84 Cressida waGN~ 90 LN3 3800, equal length headers, T70, 89 700r4, misc parts,
    1994 Oldsmobile 442 (462ci-4wd-2 engines) L67/4t80e^2,
    00 Turbo Regal 608 fwhp 575ftlbs at 5500rpm, 98 WhippledRiv, 97 GTP
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