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Thread: Open Loop AFR leaning out when hot

  1. #1
    Tuner BlackGS's Avatar
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    Aug 2007
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    Open Loop AFR leaning out when hot

    I'm running e85 on an open loop tune. During idle and cruise, one thing I've noticed is that as soon as it gets hot outside and I've been driving for a while, like over an hour, and IAT's are 100+ at idle, the AFR leans out. I try to keep AFR between 1.00 and 1.05 lambda, and that will hold perfect until it starts to heat up, then it creeps up to 1.10, and sometimes higher.

    I scan fuel pressure, and that does not change with the heat. MAF values and timing do not change either.

    Is there some other table that is not visible in HPT that could change AFR based on IAT's or some other parameter? Any other things to check?

    Hot scan and normal scan are attached. These scans were run on the same tune and same tank of gas, but the hot scan was after driving a long time and heated up, and the normal scan was from a cold start through normal operating temps.
    Last edited by BlackGS; 04-20-2012 at 06:48 AM. Reason: added cfg

    2000 Regal GS | Twin-Charged T72 | HPT Pro + PLX Wideband | 12.55 @ 110 on 15psi | Now running 20psi on E85!

    1998 5.9L Durango | Powerdyne supercharger @6psi | Mesa Headers | Gibson Cat-back | 1.7 RR's | Tuned PCM | Ported Heads | Custom TB & Intake | Custom fuel rails | Rebuild coming soon...

  2. #2
    Tuner in Training
    Join Date
    Mar 2011
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    weird, Ive noticed this as well, but never looked into it.
    10.82@126
    stock blower 3800
    http://www.youtube.com/watch?v=4gyLoTOlz4U

  3. #3
    Advanced Tuner Dr. Nopps's Avatar
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    This guy did once,
    Russ K: "Since these cars don't yet have an open loop table like the V8's and the V6 (4.3) trucks, the commanded AFR while in open loop is all over the place when not in PE. In PE the commanded AFR will be were you set it."

  4. #4
    Senior Tuner
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    Feb 2006
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    Canada
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    ^^ Beta version gives us these tables now. We got the multiplier and commanded in there for OL in the 6's
    2000 Trans Am WS6