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Thread: Big off idle stumble, whatt first? IFR? calc.vet? Something else I'm missing?

  1. #131
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    Get yourself a new set of spark plugs... yours will most likely be fouled from running rich all the time. Check your fuel rail pressure. I'll make some changes to your tune file and I'll try to get that posted here for you by tomorrow. Don't fit the new spark plugs until I give you an updated tune file to run.

  2. #132
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    Thanks! I'm going to check fuel pressure at the parts store to have that as well.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  3. #133
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    Alright, fuel pressure was 53psi with key on engine off. I flashed the converter in 4WD to prevent wheelspin and it looked like the gauge went up around 57psi, I'll reverify in the daylight tomorrow when I verify that fuel pressure holds to redline, something I should have done as soon as I put the blower on. Now that 53psi KOEO also occurs around 78kpa, so does that mean at sea level this would be 56psi? Just wondering what to put into the fuel injector calculator to reverify my IFR numbers. Also attached is the latest tune. This impact map seemed to be the best blend of starting, cold, and warm running. Not perfect, but a step in the right direction.

    411 Transient Round 22 Stock Shape Blend With Good 80 Values.ctz

    I started with a stock map that was bumped about 32%, dumped in the values I came up with at 80C (which I still may recurve), and did a linear fill from -40 to 80, then 80-140. Rudimentary, but more in line with what the motor wants. And I'm not exceeding any limits this time.
    Last edited by Supercharged111; December 28th, 2019 at 01:38 PM.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  4. #134
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    Alright... I've made some changes. It's a rough cut, so don't expect big things from it. Install your new spark plugs and do a log which includes the cold start. Then log a drive. Then when you end the log and shut down the engine, let it stand for about 10mins before restarting... then do a new log which includes the hot restart. Then post your logs and let me know how the changes felt.
    Attached Files Attached Files

  5. #135
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    Quote Originally Posted by statesman View Post
    Alright... I've made some changes. It's a rough cut, so don't expect big things from it. Install your new spark plugs and do a log which includes the cold start. Then log a drive. Then when you end the log and shut down the engine, let it stand for about 10mins before restarting... then do a new log which includes the hot restart. Then post your logs and let me know how the changes felt.
    Do you need any more/less PIDs than what I have in the log above?
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  6. #136
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    I was able to verify in the daylight today that my fuel pressure holds all the way to a WOT shift so it's good to know for sure I'm not tuning around that. I figured the pump was enough especially with me up at altitude. I should recheck at a lower altitude too. Below are the 2 logs, one of the cold start and drive and the other from the hot restart. For some reason, the only way to get EFILive to see the external WB, I have to go into the handheld every time I hook it up and select display O2. You'll notice in the hot restart there was no AFR so I shut the truck off, got the wideband displaying, then did another restart. I also changed cylinder volume back to 713 from 708 as it is a GenI 350, not a GenIII LS1. It's misleading me putting the thread in here years ago, but the truck does run off of a GenIII PCM.


    Statesman Log.efi

    Statesman Hot Restart.efi
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  7. #137
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    Okay, here's the next rough cut. This time I've set it to run MAF only. The stumble may be slightly worse on this calibration, but this is just to get a baseline so suck it up. And yeah, I gave you back the cc's I took off you in the last update. I've reduced your IFR, so you will be a little bit richer... but that's okay as you're a little bit lean now. I also changed your PE entry conditions to something a little bit safer than what you had. I will need you to log specific PIDs this time...

    Wideband
    Narrowbands
    STFT (both banks)
    LTFT (both banks)
    GM.VOLTS
    MAP
    MAF airflow
    MAF frequency
    RPM
    ECT
    IAT
    TP
    VSS
    Commanded AFR

    Don't log anything extra, just what I asked for.

    I'll need a log with about 12,000 frames of driving on warm engine. Try to get a good mix of driving.... 12,000 frames just crusing down the highway isn't very helpful... and remember to make sure your wideband engages.

    This calibration has DFCO disabled, so if you want DFCO then re-enable it after you do the log.
    Attached Files Attached Files

  8. #138
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    Actually the impact table changes made a night and day difference in the truck. That still doesn't fix the IFR/MAF/VE (or idle airflow) that we both know was off so I'm holding off on any more of that until after this is done. Here's the log, it came in around 18,000 frames. I had to go north of 12,000 because of how much of the drive was downhill. Here you're either going up one or down one. The truck actually drove fine MAF only, so I'll just leave that on for now. Thanks for all your help and collective patience with me. Going back through this thread is painful even for me at times.

    Statesman Log MAF Only.efi
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  9. #139
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    You're dangerously lean in boost. I'm not going to help you damage your engine. If you want my continued help, then you'll have to fit a boost referenced fuel pressure regulator and make a new log.

  10. #140
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    That is a vacuum/boost referenced regulator. It idles at 48, has 53 when you turn the key on and the pump primes, and holds 57 under boost. I figured it was lean because it was MAF only and that that pointed to a MAF calibration issue.
    Last edited by Supercharged111; December 30th, 2019 at 02:33 AM.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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