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Thread: changing injectors question about startup

  1. #1
    Electronic Ignition!
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    changing injectors question about startup

    Im going from 30# to 60# injectors. Will the car even start or do I need to make some tune adjustments before starting and data logging? thanks

  2. #2
    Super Moderator dave w's Avatar
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    The quick answer is yes, the injector flow rate will need to be changed.

    dave w

  3. #3
    Electronic Ignition!
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    Ok thats not a problem

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    Super Moderator dave w's Avatar
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    More often than not: what an injector is rated to flow vs. what an injector is actually flowing vs. the injector flow rate programmed into the .bin file . . . will be different flow rates.

    dave w

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    Electronic Ignition!
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    Supposedly the injectors come with flow sheets for my actual injectors

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    Quote Originally Posted by MWILSON1995Z View Post
    Supposedly the injectors come with flow sheets for my actual injectors
    Assuming the flow sheets actually apply to your injectors (there are several places out there that are NOT Fuel Injector Dynamics, that provide flow sheets that look like FID flow sheets, but turn out not to be), you'll have all the info you'll need to adjust not only the basic flow rate, but the low voltage / low pulsewidth behavior as well.
    THEY are NOT Lying to You. You are NOT Lying to Yourself. You ARE Being Lied to - BY Your Self
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  7. #7
    Electronic Ignition!
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    Im very new at this I bought CATS Tuning software the only changes Ive made are to the Fuel & Timing at WOT and I changed it when I swapped the injectors I have now ( not a big difference from stock though ) and I changed it when I changed gears but thats the extent of my tuning experience

  8. #8
    Fuel Injected! spfautsch's Avatar
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    You should really give more information about what you're tuning, mods, etc. up front. Save everybody the time and trouble of going and reading the introductions forum.

    So you're running a '95 LT-1 with the 292XFI? I'm interested how this sounds and smells at idle, I run a 280XFI N/A with 42lb injectors.

    Anyway, going from 24lb to 30lb injectors isn't a big change. 30lb to 60lb you're going to have all sorts of starting problems that won't be addressed by simply changing the static flow constant. The prime pulsewidth table will need some tweaks, and it has it's own multiplier that will need to be scaled based on the change so you don't end up flooding the bejeezus out of it. A couple years ago kur4o and I worked on this and as a result I built a spreadsheet that may save you a bunch of time and frustration. I'll try to find the thread and update this one with a link. But if I forget to let me know and I can probably find the spreadsheet easier.

    Edit: I located the aforementioned thread and realized it wasn't focused much on the start-up (prime pulsewidth) tables. Gimme a day or so and I'll write up a readme for the spreadsheet and put a link to it all in my signature.

  9. #9
    Electronic Ignition!
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    Quote Originally Posted by spfautsch View Post
    You should really give more information about what you're tuning, mods, etc. up front.

    358 ci LT1 all forged bottom end 10.3:1
    Trick Flow 185cc heads, 5 angle VJ all 7/16 hardware SS 1.6 Rockers
    Springs are set at 160# @ 1.895 & 425# @ 1.295
    292XFI HR13
    Factory Intake with BBK 58mm TB
    Dougs 1 3/4" headers off road X with original flowmaster 40
    Powerdyne BD11A @ 7-8psi draw thru Maf sensor
    ARP studs everywhere
    Canton racing oil pan & valve covers
    Still running Optispark buit everything is new and working for now!

    Thank you for any help! I have EE Hack I use for data logging and Flash hack for writing, tuner CATS for making adjustments
    Last edited by MWILSON1995Z; 2 Weeks Ago at 04:05 PM.

  10. #10
    Fuel Injected! spfautsch's Avatar
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    Sig is updated. Unfortunately I think you'll need to use TunerProRT because I'm not sure tunercat has the base pulsewidth multiplier defined. Also the readme is written specifically for TunerPro. If you have any feedback feel free to PM me or post here, I don't think anyone has used this other than myself.

    I didn't catch the supercharger in your introduction post - so are you running pure MAF or do you have patches for >1bar MAP (if such a patch exists)? Intercooler?

  11. #11
    Electronic Ignition!
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    I see the following:

    ECM Constants Table
    Minimum Injector Pulse Width--------1.099 msec

    I also have MAF sensor tables

    I just ordered an integrated AFR guage with 2 oxegen sensors for data logging

  12. #12
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by MWILSON1995Z View Post
    I see the following:

    ECM Constants Table
    Minimum Injector Pulse Width--------1.099 msec
    If you look at your bin with the .xdf in the startup tables zip in TunerPro, there are actually two values that need to be changed here. The factory bin has 1.44 ms in both. One is the threshold, and the other is the value used when the threshold is reached. I think it's labeled '126d7 - use this value when MIN inj pulse reached'. I have mine set thusly:

    126d5 : 0x002f (0.73 ms)
    126d7 : 0x0030 (0.075 ms)

    The larger # in the second constant is just to make sure the injector actually fires. I've never seen pulsewidths commanded this low, and you probably won't either, but it doesn't hurt to be thorough.

    Addition items you'll want to modify are the 129f5 Injector Offset Adder table, and 129d5 Injector Voltage Offsets.

    For the offset adder table, most folks zero this out because the bosch style injectors flow more below the knee (the point where the injector's flow rate goes static). The original Multec injectors have a lower flow rate below the knee.

    The voltage offsets should have been provided by the vendor. You may have to interpolate some of the voltage points, but all that's critical here are the voltage range you'll actually be running in, say 7-16 volts.

  13. #13
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    If I load my bin in Tuner Pro I really dont know where to go from there and I dont think I have an XDF file? Im used to Tuner CAT which Im new at as well.

  14. #14
    Electronic Ignition!
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    Typical Flow Rate in LB per hour: 60 LBS/HR @ 45 PSI
    Typical Flow Rate in CC per minute: 630 CC/min @ 45 PSI
    Actual flow rate of your injectors may vary but will be matched together ( mine vary from 54.5-55.5 )
    Resistance: 10 ohms (High Impedance, High Resistance)
    Voltage: 8-15 Volts, nominal 13.5 Volts
    Amperage: 1.0 Amps
    Pressure: Min 30 PSIG / Max 100 PSIG
    Electrical connector type: EV1 (Minitimer, Jetronic)

  15. #15
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by MWILSON1995Z View Post
    If I load my bin in Tuner Pro I really dont know where to go from there and I dont think I have an XDF file? Im used to Tuner CAT which Im new at as well.
    There's a readme file in the spreadsheet package in my sig that will get you started crawling with TunerPro. That's as close to spoon feeding you're going to get out of me, sorry.

    As I mentioned in the PM, 1 lb/hr difference in a set of matched injectors seems really excessive. But at least they gave you that data. Are these injectors new / modified / used + cleaned? You'll need an offset table for them.

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