Results 1 to 6 of 6

Thread: Issue with lean condition (AFR 16) meason wide band when forcing open loop operation

  1. #1
    Tuner in Training
    Join Date
    Jun 2010
    Posts
    11

    Issue with lean condition (AFR 16) meason wide band when forcing open loop operation

    Problem Description:
    I am suddenly having this weird problem when forcing the ECU (E38) to open loop mode for tuning.
    In this mode, my Wide Band O2 (NGK) reads AFR 16. (15.79 in the scanner Table Display) The commanded AF ratio in the table display is 14.68 and the commanded Lambda is 1.0 (I also recalibrated my wide band as a test to make sure it wasn't reading incorrectly)

    Details:
    I have forced open loop in the calibration config via setting the temperatures in ECT vs. Startup ECT and O2 Readiness ECT (152 Deg C and 256 Deg C) Also set open loop IVT gains to 1
    When the config is loaded and the engine started, the wide band reads 16. When I use VCM contols function to manually force the ECU to closed loop = on the AFR on the wideband matches the commanded AFR. When I turn closed loop off again the wide band reads AFR 16.

    When I loaded my standard config into the ECU the wide band reads as expected. When I use the Scanner to manually force closed loop off the wideband AFR reads 16 again and returns to normal operation when I turn Closed loop on again. At cold start up on the standard config when the engine is in open loop without intervention the wideband AFR reads normally.

    I did disconnect the battery for about an hour as well with no change. I also tried writing entire with no differences. I even loaded an old calibration config file that I used last year successfully via a write entire with no change to the issue so I don’t think it’s a weird setting that I accidently set. (I also used the compare function to look at every settings to determine any differences.) I also installed the wideband on the other bank in case of a weird exhaust leak.

    The issue seemed to start after I was stuck in a bad traffic jam yesterday where the engine got pretty hot. (the ECU is located under the dashboard area not in the engine compartment) The intake temp went as high as 53 Deg C. and the coolant temp went to 110 deg C.
    Application:
    The ECU is an E38 from a 2006 zo6 corvette.
    Engine is an LS7 crate motor from new in 2009. The engine has since been modified over the years to FAST 102, NW 102, Ported heads, Cam - Katech K501 (recently changed from Torquer 110), Headers etc… The engine is installed in a mid engine Kit car.

    Has anyone seen this sort of issue before?

    I will post both tunes and a log in a bit.

    Thanks for any help or ideas,
    Regards, Peter
    Last edited by GTR-P; 07-29-2014 at 10:15 PM.

  2. #2
    Tuner in Training
    Join Date
    Jun 2010
    Posts
    11
    Attached are the standard configuration file and the Open loop calibration configuration

  3. #3
    I know if I force my gen3 into OLSD via the tune and not the scanner, when I hot start it it stays at 16.00 afr untik yoy drive for 5 min or so.

    If you enter BE on a boosted setup or PE on a n/a setup the afr will go to normal. Soon as you go back to idle or parr throttle driving it would run lean as shit.

    This could be the same thing on the gen 4 but I'm not positive on that honestly. I've seen multiple ppl talk about gen 3's doing it and ways of fixing it and don't remember if anyone came up with a solution. Just the nature of the beast possibly.

    How long did you drive in OL to see if it would switch back to normal?

    I usually drive a mile or so and it goes back, then I log and tune once it is normal.

  4. #4
    Tuner in Training
    Join Date
    Jun 2010
    Posts
    11
    Thanks for the help and Ideas.
    I was able to complete some additional testing under different configurations today. My goal was to try to determine which settings or combination of settings resulted in the symptom of AFR lean condition when the ECU is forced into open loop mode via modifications the ECT (Engine coolant temperature enable stettings)
    Test process:
    Various conditions of Closed Loop enable ECT vs. Startup ECT and O2 Readiness ECT combinations were tried along with using the VCM scanner / VCM controls to toggle Closed Loop on and off as well Fuel Trim Learn on and off. The Reset Fuel Trims function was also utilized.

    General Conclusion:
    The issue seems to stem from modifications to the O2 Readiness ECT field and not the ECT vs. Startup ECT field. When using the VCM scanner / VCM control to toggle the Closed Loop on/off vs Fuel Trim Learn, the Fuel Trim Learn combined with the Resetting Fuel Trim function triggered the AFR lean Condition vs the 14.68 commanded AFR.

    It seems that there is some function based on O2 readiness and fuel trims that are corrupted somewhere that is triggered by the O2 not ready condition.

    Attached below are my test notes for reference as well as the associated logs. All testing was done while remaining stationary in idle mode.

    Test Notes:

    Test 1 log 1:
    Standard tune. No modifications to force Open loop operation
    WB AFR readings were normal at start up. Engine in open loop mode due to cold temperature.
    Used the VCM scanner / VCM control to manually toggle Closed Loop on and off. Switched Fuel trim learn on and off. Toggled Reset Fuel Trim . No change initially until the ECT started to increase. At about 80 DegC the WB AFR started to creep towards lean at 15 to 15.5 ish.

    Toggled Closed Loop ON and fuel trim learn on and the AFR returned to the expected range (14.6 ish)

    Test 2 Log 2:
    Flashed the following configuration into the ECU. ECT vs. Startup ECT set to 152 Deg C. and O2 Readiness ECT set to normal (-40 DegC). AFR were normal.
    Used the scanner to toggle Closed loop off/on. AFR remained Normal.
    Fuel Trim Learn toggled off, the AFR remained normal.
    Reset the Fuel trims and the AFR changed to a lean condition. (high 15’s)
    Toggled Fuel Trim learn On and no apparent change.
    Toggled Closed Loop On and AFR returned to Normal

    Test 3 log 3:
    Flashed the following configuration into the ECU. ECT vs. Startup ECT set normal and O2 Readiness ECT set to 256 Deg C). AFR immediately displayed 16 lean condition.
    Used the scanner to toggle Fuel trim learn ON. No change to AFR lean condition
    Toggled Fuel trim reset. No change to AFR lean condition
    Toggled Closed Loop on: AFR returned to normal.

  5. #5
    Tuner in Training
    Join Date
    Jun 2010
    Posts
    11
    Last edited by GTR-P; 07-31-2014 at 12:48 AM.

  6. #6
    Tuner in Training
    Join Date
    Sep 2012
    Location
    PA
    Posts
    46
    I've had similar issues with my '07 z06. Hope you get this figured out, as I'd like to know too!

    -Shane