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Thread: Closed loop goes rich not lean????

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    Default Closed loop goes rich not lean????

    Reference this thread for my setup and history
    https://forum.efilive.com/showthread...ics&highlight=

    I've got the tune pretty much down pat, cold start is great, idles great, A/F is good, timing is where I want it. But for the life of me when I try to go closed loop all it wants to do is pull fuel at idle and cruise, somewhere in the neighborhood of 10%. With longtubes and mods I usually see it trying to dump a bunch of fuel when you go closed loop. Has anyone seen what Im seeing, that it will trying to lean it out with closed loop? Is it just a matter of adjusting the O2 switch points to something high like 5-600mV to get it to richen up the idle and cruise when in closed loop? Thanks for any info.

  2. #2
    Joe (Moderator) joecar's Avatar
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    Post log and tune.

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    Quote Originally Posted by joecar View Post
    Post log and tune.
    This is a "warm" start as I had been messing with the MAF table and other crap to try and get it resolved. Notice the air fuel before the O2's start switching and it goes closed loop and then the air fuel after. It smells a little lean from inside the car so I think the wideband is correct. Its a brand new LC1. I can compare with an LM1 I also have if needed. I did the 02 OS flash update from the 99. Also note the air g/sec and injector data is scaled 30% and its a MAF only tune.
    Log_idle 6-30-17.efi295-50-16 TIRE-4 inch pulley CLOSED LOOP MAF ONLY_02os knock tables_30 percent scaled tune_2_idl.ctz

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    Verified the air fuel with a lm1 in place of my new lc1 and same result.

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    How are you receiving the wideband data? Serial or analog?

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    Quote Originally Posted by Team208Motorsports View Post
    How are you receiving the wideband data? Serial or analog?
    Serial only on both widebands. I've tuned quite a few cars now and this one runs great, especially given the cam and blower, but this closed loop lean business is so weird to me.

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    CL mode at idle is about 30. I think you are adjusting the wrong part of the switch point table. Adjust the switch point or adjust the CL mode table to make the switch point table proper. Remember lower vacuum cams at idle want a leaner switch point to match the wideband.

    Also, when the wide band shows mid-high 14s the narrows never dip from high mv.
    Last edited by ProperTuningOG; July 1st, 2017 at 04:19 PM.

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    Ah crap,well now I just feel lazy. I thought about CL mode and figures there was no way it was that high given that the time is scaled 30 percent, but didn't actually check it. One thing you said confused me. You said I want a leaner switch point? My understanding was the switch point table allows you to tailor what the car thinks is Rich vs. lean. I.e if I raise the switch point to 600mV, the car will spend more time on the lean side and I will have positive fuel trims, is this true?

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    I made a change to the switch points at CL mode 24 and 32 and it appears the crusing AFR is better than it was, not perfect but in the right direction. Idle still is leaner than I would want. Something of interest in the logs is at frames 3859-3943 right when the car comes to a stop. The AFR and O2's go rich like 900mV and the AFR 13.5 to 15 and then all of a sudden the O2's start switching again. This is also repeated starting at frame 6830. Should I keep pushing the switch points up until the fuel trims comes back to where they should be?
    Attached Files Attached Files

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    The log makes it seem like you are running on 2 different ground plains or something is off voltage wise with the wideband or narrows. I highlighted an area to show this. If the condition was lean the narrow mv would not be 900.

    I would disable closed loop and start looking at voltage difference under steady state with no O2 switching. If things even out as they should and its only an idle condition, then at least you have narrowed it to that. If they have not and you are still showing 900 mv condition under a steady state 14.7-15 then something is going on with data collection.

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