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Thread: Closed loop: any way to change lambda AFR?

  1. #1
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    Closed loop: any way to change lambda AFR?

    I don't suppose there is any way to change stoic in closed loop from 14.7 to a lower value is there? I thought changing the value under fuel>general>stoich AFR would do this, but it obviously doesn't do anything for closed loop as the ecm is looking at the O2's reporting +/- from lambda 1. (do I have that right?) Regardless, I changed stoich in this table to reflect 14.2, took a drive and the log shows a commanded AFR of 14.2, but my wide band shows a steady effort to maintain 14.7. So much for that brilliant idea....

    I then got to thinking that if there was a way to change lambda from 1 (14.7) to where "1" really equates to 14.2 or thereabouts, that might help with cam overlap. It's my belief that the O2's are reporting a false rich condition and leaning the engine out beyond 14.7 at the combustion chamber from a reversion induced improper combustion event.

    I have a strong preference to keep closed loop enabled, otherwise I'd just say screw it and run open loop. Where I live, I need fuel trims. I am more than willing to try any ideas and report back the results if anyone has any suggestions to offer.
    When arguing with an idiot, make sure he isn't doing the same thing....

  2. #2
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    Your wideband reads in lambda and converts it to afr. Most report lambda 1 as 14.7. You can change what your wideband reports in hptuners by changing settings. There is a spreadsheet for doing this floating around. If I can find it I will post the link.
    2007 Corvette C6 Vert. A6
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  3. #3
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    I believe it is this one although I can not confirm right now as I am on a tablet that can't open it.

    http://www.hptuners.com/forum/showpo...p;postcount=51
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    E force SC, 3.00 pulley, ID 850's
    Alky Control Meth,
    ARH 1 7/8 headers, cats, xpipe
    724 RWHP @ 6500, 866 RWT @ 3700

  4. #4
    Senior Tuner 5_Liter_Eater's Avatar
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    On the third gens you can change the switchpoint mv of the narrow bands so they think stoich is where ever you shift it to but AFAIK it doesn't work on the 4th gens.
    Bill Winters

    '05 Corvette - Iron Block 408 & TTIX - 928 RWHP / 926 RWTQ @ 21#

    "When life hands you lemons you upgrade to a C6." - Me

    Always post a tune and a log when asking questions.

  5. #5
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    If there is one Bill, I don't see it. Just mV settings for min/max rich/lean. I think 0 mV is lambda. But now that I'm looking at those, it looks like they changed them in 2011 to 450 min/max. My settings are 300 / 625, but the bank one and two settings are all 450. No idea what's going on there.
    When arguing with an idiot, make sure he isn't doing the same thing....

  6. #6
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    450mv is where you want your narrow bands to switch at for lambda.
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado

  7. #7
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    Quote Originally Posted by Gh0st View Post
    450mv is where you want your narrow bands to switch at for lambda.
    Why do you say that? I'm not doubting you, but when comparing different year Z06 tunes, the 06, 07, 08 and 09 min rich/lean is 300 mV and the max rich/lean is 625. The 2010 and 2011 has them both at 450.

    Could it be that GM changed to a different O2 sensor in 2010?
    When arguing with an idiot, make sure he isn't doing the same thing....

  8. #8
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    My 07 is set at 450 with min 300 and max 600 and it works fine like that.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    E force SC, 3.00 pulley, ID 850's
    Alky Control Meth,
    ARH 1 7/8 headers, cats, xpipe
    724 RWHP @ 6500, 866 RWT @ 3700