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Thread: PE Timing adder? Commanded advance differs from actual

  1. #1
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    Default PE Timing adder? Commanded advance differs from actual

    I could swear that PE mode adds timing, but I can't find it anywhere. I have found B5908, Fuel Mixture Spark Correction, but I don't understand its function. WOT 4400 RPM's 85kpa and 22 degrees of advance according to the main timing table. ECT and IAT's were in check so they weren't screwing with my timing, I had 1.88 degrees being pulled but the Scanner still indicated 23.5 degrees of advance being present. My altitude sucks apparently. With a full airbox I drop to 85kpa (from 88) by 3700 RPM's and with air filter and airbox lid removed I don't hit 85kpa until 4900 RPM's, is that 1-2 kpa being lost over the RPM band significant? And what am I missing? Why is more timing being added?

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    Alright I got impatient and copy/pasted this B5908 to an excel document and zeroed the thing out in the tune. Then I guesstimated a WOT timing curve and went out for a test drive. No more KR! Sweet. It even pulled a little better due to additional timing, but it was still 5 degrees shy of my main advance table from 4000+ and 2-3 lower below 4000 at 85kpa with no KR detected. What gives? My ECT was around 94C and the table doesn't pull timing until 98C. Even then it only pulls 1 degree, so it'd probably interpolate between the 2 and pull a fraction of a degree of timing. IAT's were in check, is there some torque management that I forgot about? The only torque management that I'm aware of right now is the upshift. I disabled absue mode by setting D1019 to 0.0kmh. I'm really at a loss here, this PCM is pretty bare bones so as far as I can see there aren't that many modifiers.

  3. #3
    Joe (Moderator) joecar's Avatar
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    Which PCM/vehicle/year/model...?

    Post your tune/log files, someone may have an answer.

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    Vehicle should be in my sig now, a 1998 GMC Sierra K1500 5.7/4L60E w/stock PCM. My elevation is 3200ft and I was running 87 octane. I've attached a quick 1-2 pull on 87 octane, and a larger log on 91 octane. I found last night that my PID's got screwed up somehow and the correct knock retard PID was swapped for the wrong one. I sure as hell didn't change them, I don't know why it and the commanded AFR PID's were both changed. At any rate, the most KR I log is 4 degrees, yet somehow it always manages to pull more than that. How is this possible? What is pulling the extra timing? The abuse mode I disabled? Or how about the TM that's only supposed to intrude on my upshifts? Did I miss some other TM somewhere else? Or is there a KR multiplier somewhere? Even if there was, it should tell me it's pulling 6 degrees and not lying to me telling me it's only pulling 3-4 when I'm losing 6 degrees or more. I tried retarding the timing to stay out of the detonation, but it still pulls it and I end up with way less timing and the truck falls on its face. I don't know what else to do. . . just crank up the timing so the end timing is what I want?

    Edit: Forgot to upload tune.
    Last edited by Supercharged111; March 22nd, 2009 at 08:56 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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    Right here my timing gets ganked to 11 degrees. I'm unaware of any TM on my downshifts and the main timing table calls for a good bit more than this. I must be missing something huge. I should also mention that a 180 stat is in my very near future.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by Supercharged111; March 22nd, 2009 at 09:06 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.

  6. #6
    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
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    Was your IAT was really 54C at the time?

    Your Spark IAT Table was pulling out 2-3 degrees of timing?
    Last edited by WeathermanShawn; February 9th, 2010 at 10:24 PM. Reason: Grammer
    2002 Black Camaro Z-28 M6 Hardtop 11.0:1CR 425HP/410TQ SAE (400TQ@3500RPM)
    200cc Heads, 228/232 110+2 Cam, 1 3/4" LT's w/catts, GMMG, Koni Shocks, Hotchkis Springs, 35/21 Sways, 17" ZR1's, 3.90 Gears Roadrunner PCM LM-2 Serial Wideband
    EFILive Closed-Loop MAF/SD Hybrid Tune..


  7. #7
    Lifetime Member GAMEOVER's Avatar
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    Thats kinda warm....
    2008 2WD Ext.Cab Silverado 1500 6.0 V-MAX E38(L76) & T42(4L70E) MAF Only CL Corvette Servo AFE CAI INNOVATIVE LM-2 WBO2

    FLASHSCAN V2 & AUTOCAL

  8. #8
    Lifetime Member GAMEOVER's Avatar
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    How much timing did you add? Post up your stock tune...
    2008 2WD Ext.Cab Silverado 1500 6.0 V-MAX E38(L76) & T42(4L70E) MAF Only CL Corvette Servo AFE CAI INNOVATIVE LM-2 WBO2

    FLASHSCAN V2 & AUTOCAL

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    Dammit, stupid IAT's. You're right, there's a couple degrees on the WOT for sure. But that still doesn't account for the rest of the lost timing on the screenshot: I'm losing like 6-7 degrees with no knock retard. 2-3 can be chalked up to IAT's (need to reinstall airbox lid) but I'm starting to think the rest are some TM that I didn't successfully disable. And why in God's name will this thing not take what, like 26 degrees of advance?! What a crock! Here's the stock tune for your viewing pleasure, please note that my tune has B5908 0'd out and the rest added into the main table. When I logged mapped RPM vs TPS for knock (in an effort to see if high loads outside of PE mode would induce detonation) I found most of my knock to be in the WOT and some in the cruising RPM/load cells encountered in OD at 70mph so thus far zeroing that table appears to be a success to me.
    Last edited by Supercharged111; March 22nd, 2009 at 01:41 PM. Reason: Forgot to attach map
    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.

  10. #10
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    Just for a quick visual, it looks like my values hover around the stock values very closely, but I choose to ramp up the timing more slowly and give more in the end instead of taking it away as RPM's climb. Unlike the stock tune, which has the most advance at peak torque (?!) mine is milder at peak torque and advances after peak torque. Below are the values of the stock tune and my current tune at 85kpa:

    85kpa 2400 2800 3200 3600 4000 4400 4800 5200
    stock 23+2 25+3 25+3 24+3 21+3 20+4 20+4 20+3
    mine 24 24 25 25 26 26 26 26

    I should also mention that I don't have problems until after peak torque is achieved. I really need to hook up the wideband to make sure commanded AFR's are what they claim to be, but they can't be that far off right? Engine's bone stock, stock exhaust, stock paper air filter!
    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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