Ideal Wideband AFR at idle?

Posted by 9!'clipseDOHC, May 5, 2010
Tuning & Engine Management - 4G63 EPROMS, ECU, MAF, knock, EGT, wideband, datalogging, fuel trims, etc. Read this Forum's Strict Guidelines.

  1. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    Exactly as the title states. What is the normal or ideal wideband o2 AFR reading when idling at 750 rpms? I searched but got nothing. On my turbo swap, fresh rebuild (profile is current), brand new AEM wideband installed on the downpipe, after the bend, before the flex. Super lean with factory injectors, 14b, no tuning device at idle.

    AFPR is set at 37 with the hose off
    Timing is 5 BTDC
    Idle is 750-800
    AFR is 17 to ---

    Is this good or bad? When I drive the AFR falls, haven't been WOT or even over 2500 rpms yet. I need the rest of my exhaust before I can take it on the roads.
    #1
  2. knochgoon24

    knochgoon24 DSM Wiseman

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    It should cycle around 14.7 once it's warmed up.
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  3. steve

    steve DSM Wiseman

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    How/what are you using to provide the narrowband input to the ECU required to support the ECU going into closed loop?

    Without it the ECU will go into a limp mode.
    #3
  4. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    I have a brand new NTK o2 sensor in the o2 sensor housing.
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  5. steve

    steve DSM Wiseman

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    Good. Is the narrowband cycling?

    If the wideband isn't tracking it as the ECU dithers the AFR to cause the NB to switch then you might have a leak between the two or drawing fresh air in the unfinished exhaust and throwing the reading off.
    #5
  6. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    How would I tell if the narrowband is cycling?

    The exhaust ends at the downpipe for the moment, I hadn't thought about that making it read lean. Hmm. I hope to have the rest of the exhaust by the end of the week.
    #6
  7. steve

    steve DSM Wiseman

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    Datalogger or voltmeter.
    #7
  8. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    I have a voltmeter, no dataloger yet (v3 lite is next on my list).
    #8
  9. 2gGSXEclipse

    2gGSXEclipse Proven Member

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    Should be near 12.0 on a cold start and lean out as the car gets warmer.
    #9
  10. rarest_90_DsM

    rarest_90_DsM Proven Member

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    mine starts at 13-14 when cold then when it warms up its anywhere from 14.5-16 u get your wideband new or used?
    #10
  11. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    Wideband is brand new. It's an AEM UEGO Wideband.
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  12. rarest_90_DsM

    rarest_90_DsM Proven Member

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    do you have the gauge set right there's a little dial on the back of the gauge that they swear the set on lambda before the leave the factory, but i would double check it with your owners manual. If that doesn't work i would check your ignition timing probably advanced to much.
    #12
  13. nightracer91

    nightracer91 Supporting Member

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    With my EMS, I have to keep the idle between 13.4-13.9 AFR. Having the 272's, 14.7 while idling will cause it to surge. So I had to richen it up a pinch and turn the idle up to about 950.

    Definately check for exhaust leaks, air could easily be back feeding into your open downpipe giving leaner-than-normal readings.
    #13
  14. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    Thanks for all the numbers. I must have an exhaust leak. I got the rest of the exhaust bolted up and i'm still getting --- at idle. Driving everything is good, high 14's/low 15's cruising. High 12's/low 13's boosting (set at factory boost, about 11 psi, while I break the engine in). But when I idle or am off the gas, high 17's and then off the gauge.

    I have a 2g o2 housing feeding into a 3" punishment racing downpipe, I think the leak is there because I can't get a socket on the nuts. I'll have to work with it some more.
    #14
  15. turbotalon31

    turbotalon31 Proven Member

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    had the same issue and it was exhaust leak at the o2 housing and the downpipe.
    #15
  16. nightracer91

    nightracer91 Supporting Member

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    I had a similar leak there also. I ended up switching the 19mm nuts to 17mm with the same threads inside so I could get a socket on them. They haven't backed off yet.
    #16
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  17. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    I was just told the same thing today by the guy who built my block. Good advice! Do you remember the thread size? Also where did you find the nuts?
    #17
  18. We're on Boost

    We're on Boost Proven Member

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    Here's what I did to solve that problem on my car:


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    Did the grinding on the tips of this crowfoot with a bench grinder and cold water for dunking. Those stock 19mm nuts are super quality if they haven't been rounded or rusted.
    #18
  19. nightracer91

    nightracer91 Supporting Member

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    The crows foot works too but I just dug through my bolt drawers and found 2 17mm nuts. The thread is 12 x 1.25 i believe but I'm not 100% on that.
    #19

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