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Thread: Question on tuning LARGE INJECTORS

  1. #1
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    Default Question on tuning LARGE INJECTORS

    I have 60lb/hr Mototron injectors and I am having difficulty tuning below 40KP of manifold pressure. During AutoVE it always tells me to subtract like 20-25% of the table below 40KP and everytime I am off the throttle my engine runs WAY rich (10-11:1), I remember reading on here that I can play with the Pulse Width in that area in the V vs RPM table but I have also read not to.
    Could anyone shed some light on this for me?

  2. #2
    Lifetime Member TAQuickness's Avatar
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    Click the reference material link in my sig, then "tuning for big injectors" - lot's of good info and might be all you need. If that doesn't work, post back here.


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    Well I am going through your list of things to do and I am having small amounts of luck but no major progress. It does feel like I have cleaned up the idle a tad but I still get overly rich on decel.
    Does anyone know if my injectors are plate style or pintle??? Also... Does anyone know what is the minimum pulse width I should command with these?
    Thanks again!

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    Well I did find some info on these injectors...
    On time is 1.14ms and off time is .85ms. So I gues I should change my default Minimum Injector Pulse Width to 1.14???? I am still confused though on what I should set my Low Pulse Threshold to though... Any ideas?
    Also... I started upping the flow rates under 35KPA and that did make a bit of difference. No where near right yet but getting there. I think I went a little too far the first time though because I went to start it and I got nothing but cranking!

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    Lifetime Member TAQuickness's Avatar
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    What's your fuel pressure?


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    Stock at 58 PSI, I guess it would help if I had a set pressure of 43 PSI since thats what these were rated at. The fuel system is stock except for a walbro pump and the injectors.
    Anyone know if they make a LS1 style fuel pressure regulator set for a loer pressure that I could swap into the gas tank????

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    Lifetime Member SSpdDmon's Avatar
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    Quote Originally Posted by RacerChris View Post
    Well I did find some info on these injectors...
    On time is 1.14ms and off time is .85ms. So I gues I should change my default Minimum Injector Pulse Width to 1.14???? I am still confused though on what I should set my Low Pulse Threshold to though... Any ideas?
    Also... I started upping the flow rates under 35KPA and that did make a bit of difference. No where near right yet but getting there. I think I went a little too far the first time though because I went to start it and I got nothing but cranking!
    The actual minimum on/off times of the injector are the min pulse width PLUS the battery voltage offset PLUS the short pulse adder. With my stock internals LS1, I need a pulse width of 1.6~1.7ms for a stoich idle with my Motron 60s. I had to play with the voltage offset table and zero out the small pulse adder to get the idle AFR to a reasonable level.

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    Quote Originally Posted by SSpdDmon View Post
    The actual minimum on/off times of the injector are the min pulse width PLUS the battery voltage offset PLUS the short pulse adder. With my stock internals LS1, I need a pulse width of 1.6~1.7ms for a stoich idle with my Motron 60s. I had to play with the voltage offset table and zero out the small pulse adder to get the idle AFR to a reasonable level.

    I will be sure to adjust this tonight and try a few logs. I will report back tomorrow.
    Thanks again

  9. #9
    Senior Member exploder's Avatar
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    I have 96lb low impedence injectors in mine....here is my tune file and I have them running good at idle.
    Attached Files Attached Files
    03 z06 auto
    ver7.5.5 custom OS5
    415 ci
    239/255 .624 lift LSr grind
    16psi
    Meth injection
    PLX WB02

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    Quote Originally Posted by exploder View Post
    I have 96lb low impedence injectors in mine....here is my tune file and I have them running good at idle.
    Thanks for sharing your tune, I dont believe it will do much good though because our injectors will have completely different personalities.
    However, after looking at your tune I noticed that your VE tables were pretty spiky, are you finished tuning it??? If so you may want to take another go at it and do some smoothing.

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