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Thread: HELP ME PLEASE!!! Minimum pulse width?

  1. #1
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    Angry HELP ME PLEASE!!! Minimum pulse width?

    Guys this has been killing me, literally... So I'm gonna do my best to try to explain whats going on here.

    I'm working on my brothers 1971 Nova, LQ4/4L80e/Turbo swap. 2000 Z28 harness and ECM. 02020005 Custom OS (based it off of a 12212156 2002 Z28 file).

    On his first build we had some what we believed to be Siemens Deka 60# injectors, thats where it all started SMH... I got inj data from FIC for those, typed it all up in the tune, but right off the bat, tune seemed rich everywhere in light throttle areas and lean in heavy throttle areas, as if the injectors weren't very linear. Called FIC, they were maybe assuming i didn't know much about tuning, after i explained i had been successfully tuning cars for over 9 yrs he started to think the injectors might be ebay knock offs. We sold those and bought some new 95# FIC's.

    Well after installing the new FIC 1000cc Bosch injectors, I started from scratch with a new tune WITH FIC injector data just how I've normally done successfully with all my builds. Started the car and immediately noticed it was rich at idle and light throttle just sitting there, so started taking fuel out of the VE table, but it made no difference, i even tried drastic numbers like -200%, no difference. I sized the injectors bigger in the tune and that did the trick. Finally got the STFT close to 0% at idle and very light throttle, but then any moderate throttle it would go extremely lean, even with the VE at like over 120% at 12psi map and it was still lean.

    I moved the injector flow rate back to where they were supposed to be and noticed that the minimum pulse width the PCM would ever command was around 2.319ms. So at idle and and light throttles it would never command less than 2.319ms, EVEN if i commanded leaner AFR in the DVT section of the scantool.

    DATALOG ATTACHED

    So here's whats weird, IF i turn fuel trims on, it'll pull fuel and idle/cruise 14.6 AFR... some times itll pull upto -70%, the problem with that is then when you tip into the throttle it will hesitate and go lean for a sec before it recovers.

    SOOOOO FRUSTRATING!!!!!

    Ive been tuning Gen3 LS' stuff for over 10 years, never had this problem before. In fact, Ive tuned multiple trucks also with FIC 95's and never had this problem. I figured there must be an underlying issue, but today I was tuning another car with nearly the same setup (except 5.3 and truck harness) and it is doing the exact same thing to me...

    MY BROTHERS TUNE AND A DATA LOG IS ATTACHED


    Log_2G1FP22G5Y2146330_0032.efi

    NEW_NOVA_TURBO_0018.ctz

  2. #2
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    Also, some stuff may look a bit wacky in the tune and thats because those settings seem to help a little.
    -John

    1991 RCSB 2WD Sierra LQ4 swap, 220/224 112 cam, Twin VSR 6766 turbos
    4L80e w/shift kit, PY 3600, and 3.73 gears.
    22 PSI and E85, 4300# with driver. 9.7@138, 1.47 sixty
    :drivin:

  3. #3
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    Wow, those must be some kind of trick/magic injectors to have minimum PWs that low. Care to share the supplied injector data? Why no wideband in the log?
    Last edited by ProperTuningOG; June 19th, 2017 at 01:52 PM.

  4. #4
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    Now I messed with B4006 (small pulse threshold) and set it real low, seemed to help a little. It's supposed to be at 2.500. Also B4003 and B4004 are both supposed to be .125 across the board. I also messed with B3701 a little. But like I said that doesn't help at all.

    Site wont let me upload the inj data sheet from FIC.
    -John

    1991 RCSB 2WD Sierra LQ4 swap, 220/224 112 cam, Twin VSR 6766 turbos
    4L80e w/shift kit, PY 3600, and 3.73 gears.
    22 PSI and E85, 4300# with driver. 9.7@138, 1.47 sixty
    :drivin:

  5. #5
    Joe (Moderator) joecar's Avatar
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    Hi John,

    Questions:
    a. is the FPR manifold referenced (expected answer = yes)...?
    b. are you getting an immediate MAF DTC (expected answer = yes)...?

  6. #6
    Joe (Moderator) joecar's Avatar
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    ( BTW: set B3609 to 0.050 s )

  7. #7
    Joe (Moderator) joecar's Avatar
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    Commanded AFR is doing strange movements...

  8. #8
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    Do you understand what all the injector setup does? You need to eliminate the error in the opening and closing times below sustainable accurate pulse width. The way you have things setup is not correct, you have eliminated all small pulse correction. This is why I asked for the injector data. Seeing an injector that size with a sustainable non corrected minimum PW of 0.151975 would be straight magic. I know you are gonna say where the data came from and its been a decade worth of tuning. Proper setup of base calculations kills majority of tuning issues. Understanding what the ECM does with this data is just as important as using accurate external devices to collect the needed data for tuning.

    You have not changed the minimum transient setting B9021, its still set as stock 5.7.

  9. #9
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    Quote Originally Posted by joecar View Post
    Hi John,

    Questions:
    a. is the FPR manifold referenced (expected answer = yes)...?
    b. are you getting an immediate MAF DTC (expected answer = yes)...?
    Yes and yes

    Quote Originally Posted by joecar View Post
    Commanded AFR is doing strange movements...
    That was me commanding it to in the DVT controls. As you can see injector pulse width does not drop, even when afr is commanded really high, however when I richen it up, it responds fine.
    Last edited by LS1FREEK; June 20th, 2017 at 07:24 AM.
    -John

    1991 RCSB 2WD Sierra LQ4 swap, 220/224 112 cam, Twin VSR 6766 turbos
    4L80e w/shift kit, PY 3600, and 3.73 gears.
    22 PSI and E85, 4300# with driver. 9.7@138, 1.47 sixty
    :drivin:

  10. #10
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    Quote Originally Posted by Team208Motorsports View Post
    Do you understand what all the injector setup does? You need to eliminate the error in the opening and closing times below sustainable accurate pulse width. The way you have things setup is not correct, you have eliminated all small pulse correction. This is why I asked for the injector data. Seeing an injector that size with a sustainable non corrected minimum PW of 0.151975 would be straight magic. I know you are gonna say where the data came from and its been a decade worth of tuning. Proper setup of base calculations kills majority of tuning issues. Understanding what the ECM does with this data is just as important as using accurate external devices to collect the needed data for tuning.

    You have not changed the minimum transient setting B9021, its still set as stock 5.7.
    Like I said, all these problems were and still are problems even when I had the set the way they're supposed to be 2.5ms on the small pulse threshold. And minimum pulse width is supposed to be .125ms, according to data. For some reason my search isn't coming up with anything when I search B9021.
    -John

    1991 RCSB 2WD Sierra LQ4 swap, 220/224 112 cam, Twin VSR 6766 turbos
    4L80e w/shift kit, PY 3600, and 3.73 gears.
    22 PSI and E85, 4300# with driver. 9.7@138, 1.47 sixty
    :drivin:

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