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Thread: Proper scaling and pulse width figures for GM Part # 24508208 injectors???

  1. #1
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    Proper scaling and pulse width figures for GM Part # 24508208 injectors???

    From what I can find, these injectors flow 42lb on a 58psi rail, rated at 43.5 psi. Using "The tuning school" way of imputing the injector flow rate into the table, and dropping pulse width down to the .950 range I can't get this car to smooth out on the VE. No matter what I adjust with the injector flow rate, I get constant rich/lean conditions in the VE with huge spikes. It will not smooth out, and the car runs like crap in both VE and MAF mode while trying to tune.

    FYI, the "tuning school" way of doing it in their book is to look at the stock injector table. Subtract the figure @ Zero KPA from the figured @ 80kpa. Which was 2.6. Then calculate flow date of new injectors which according to the HPtuners calculator was 48.5. Put 48.5 in the zero KPA cell, add 2.6, which was 51.1 and add it to the 80kpa cell. Then "interpolate section" to fill the rest of the data.

    Where can I get the correct data to get these injectors input correctly? Also, what other tables besides pulse width should be modified?

    Thanks
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  2. #2
    Advanced Tuner 69lt1bird's Avatar
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    These are stock GM injectors, everything I found on them shows 42 lbs @ 58 and they are also for the old SC 3800, 36 lb @ 43 psi. You should be able to leave everything else alone and just rescale the IFR table.

    Go here and use the IFR calculator and plug the numbers into your table.
    http://ls1tuningguide.com/tuninghelpfiles.php
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    1969 Firebird: 11.67@114 7.55@97.93 1/8 1.70 60 ft. EPS cam 234/246 .602.606 114+3, 6.0 LQ4, L92 heads milled 10.5:1, Ported L76 intake, ported 90mm Holley TB, 100mm MAF, FIC Custom injectors, Hooker LT, PYPES dual exhaust with an X pipe, 4L65e with all of the good parts inside, FTI 4000 RPM Stall, 12 bolt with 3.73 gears. HP Tuner tuned by me

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    So leave pulse width tables alone also?

    Thank you for the link.

  4. #4
    Advanced Tuner 69lt1bird's Avatar
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    According to the links that I saw, people just dropped them in and only adjusted the IFR to match the LS1 fuel pressure.
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    Michigan Snowmobiler

    1969 Firebird: 11.67@114 7.55@97.93 1/8 1.70 60 ft. EPS cam 234/246 .602.606 114+3, 6.0 LQ4, L92 heads milled 10.5:1, Ported L76 intake, ported 90mm Holley TB, 100mm MAF, FIC Custom injectors, Hooker LT, PYPES dual exhaust with an X pipe, 4L65e with all of the good parts inside, FTI 4000 RPM Stall, 12 bolt with 3.73 gears. HP Tuner tuned by me

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    Leaving the pulse width alone isn't working. Any other ideas ?

  6. #6
    Advanced Tuner 69lt1bird's Avatar
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    What is your base tune from?
    Free HP Tuners Beginners Tuning Guide

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    Michigan Snowmobiler

    1969 Firebird: 11.67@114 7.55@97.93 1/8 1.70 60 ft. EPS cam 234/246 .602.606 114+3, 6.0 LQ4, L92 heads milled 10.5:1, Ported L76 intake, ported 90mm Holley TB, 100mm MAF, FIC Custom injectors, Hooker LT, PYPES dual exhaust with an X pipe, 4L65e with all of the good parts inside, FTI 4000 RPM Stall, 12 bolt with 3.73 gears. HP Tuner tuned by me

  7. #7
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    Quote Originally Posted by That_guy View Post
    Leaving the pulse width alone isn't working. Any other ideas ?
    Of course and it's not going to work. It is a completely different injector than the injector that comes stock and the offsets, min. pulsewidth, short pulse adder, etc... for the stock injectors arent going to have your fueling right.

    It doesnt matter if the injector you are using now was used in a GM application or not just changing the IFR when changing any injectors is not going to work unless all of the fueling error is baked into the ve/maf which is not a good road to go down.
    2005 Silverado Crew Cab 2wd

  8. #8
    Advanced Tuner 69lt1bird's Avatar
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    Scroll down to post #10, FAST uses these http://www.ls1tech.com/forums/fuelin...or-advice.html as drop in upgrades for the LS1. If you are set on using these, you could start with the injector tables for a 2000 Camaro and just try changing the IFR to see what happens.

    Of course, if you already played with the VE and MAF tables you will need to do those over again.
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    Michigan Snowmobiler

    1969 Firebird: 11.67@114 7.55@97.93 1/8 1.70 60 ft. EPS cam 234/246 .602.606 114+3, 6.0 LQ4, L92 heads milled 10.5:1, Ported L76 intake, ported 90mm Holley TB, 100mm MAF, FIC Custom injectors, Hooker LT, PYPES dual exhaust with an X pipe, 4L65e with all of the good parts inside, FTI 4000 RPM Stall, 12 bolt with 3.73 gears. HP Tuner tuned by me

  9. #9
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    Quote Originally Posted by 69lt1bird View Post
    What is your base tune from?
    A local shop that did a generic flash just to get the car running for this guy. On the injector table in the "base" he just merely added 20 all the way across.

  10. #10
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    Quote Originally Posted by KLUG'S SS View Post
    Of course and it's not going to work. It is a completely different injector than the injector that comes stock and the offsets, min. pulsewidth, short pulse adder, etc... for the stock injectors arent going to have your fueling right.

    It doesnt matter if the injector you are using now was used in a GM application or not just changing the IFR when changing any injectors is not going to work unless all of the fueling error is baked into the ve/maf which is not a good road to go down.
    Awesome. Sooooo......how do you properly calculate pulse width?

  11. #11
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    Quote Originally Posted by That_guy View Post
    Awesome. Sooooo......how do you properly calculate pulse width?
    Well you have 2 options, one involves alot of logging/ driving make changes to offsets, short pulse adder, etc... Until you get things close which I have done when I was dealing with an injector with incomplete data because I refuse to rape the ve/maf tables or choose a different injector with better readily available data.


    The big question you need to ask yourself is how well were the ve/maf tables tuned previously with good known injector data? If it was really close before then that sure keeps you from chasing your tail even more.
    Last edited by KLUG'S SS; 09-21-2010 at 01:12 PM.
    2005 Silverado Crew Cab 2wd

  12. #12
    Advanced Tuner 69lt1bird's Avatar
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    2 other options. Put in all of the injector data for a 2000 F car and change the IFR to match your injectors to see if it works.

    Second, sell the 36's and call FIC and get a different set that is easy to tune.
    Free HP Tuners Beginners Tuning Guide

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    Michigan Snowmobiler

    1969 Firebird: 11.67@114 7.55@97.93 1/8 1.70 60 ft. EPS cam 234/246 .602.606 114+3, 6.0 LQ4, L92 heads milled 10.5:1, Ported L76 intake, ported 90mm Holley TB, 100mm MAF, FIC Custom injectors, Hooker LT, PYPES dual exhaust with an X pipe, 4L65e with all of the good parts inside, FTI 4000 RPM Stall, 12 bolt with 3.73 gears. HP Tuner tuned by me