Ideal Wideband AFR at idle?

Posted by 9!'clipseDOHC, May 5, 2010

Please Support Boostin Performance
  1. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    3,455
    184
    Joined Aug 24, 2003
    El Paso, Texas
    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.
     

    Log in/Register to remove ads
    My DSM:
    1991 Mitsubishi Eclipse GSX

    Street Build

    13.102 @ 111.220 MPH
    Loading...
  2. knochgoon24

    knochgoon24 DSM Wiseman

    4,747
    60
    Joined Jan 29, 2008
    Troy, Michigan
    It should cycle around 14.7 once it's warmed up.
     
    Loading...
  3. steve

    steve DSM Wiseman

    12,420
    358
    Joined Feb 3, 2002
    St. Charles, Illinois
    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.
     
    My DSM:
    Loading...
  4. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    3,455
    184
    Joined Aug 24, 2003
    El Paso, Texas
    I have a brand new NTK o2 sensor in the o2 sensor housing.
     
    My DSM:
    1991 Mitsubishi Eclipse GSX

    Street Build

    13.102 @ 111.220 MPH
    Loading...
  5. steve

    steve DSM Wiseman

    12,420
    358
    Joined Feb 3, 2002
    St. Charles, Illinois
    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.
     
    My DSM:
    Loading...
  6. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    3,455
    184
    Joined Aug 24, 2003
    El Paso, Texas
    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.
     
    My DSM:
    1991 Mitsubishi Eclipse GSX

    Street Build

    13.102 @ 111.220 MPH
    Loading...
  7. steve

    steve DSM Wiseman

    12,420
    358
    Joined Feb 3, 2002
    St. Charles, Illinois
    Datalogger or voltmeter.
     
    My DSM:
    Loading...
  8. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    3,455
    184
    Joined Aug 24, 2003
    El Paso, Texas
    I have a voltmeter, no dataloger yet (v3 lite is next on my list).
     
    My DSM:
    1991 Mitsubishi Eclipse GSX

    Street Build

    13.102 @ 111.220 MPH
    Loading...
  9. 2gGSXEclipse

    2gGSXEclipse Proven Member

    356
    3
    Joined Apr 7, 2008
    847, Illinois
    Should be near 12.0 on a cold start and lean out as the car gets warmer.
     
    My DSM:
    Loading...
  10. rarest_90_DsM

    rarest_90_DsM Proven Member

    268
    3
    Joined Jul 21, 2004
    akron, Ohio
    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?
     
    My DSM:
    Loading...
  11. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    3,455
    184
    Joined Aug 24, 2003
    El Paso, Texas
    Wideband is brand new. It's an AEM UEGO Wideband.
     
    My DSM:
    1991 Mitsubishi Eclipse GSX

    Street Build

    13.102 @ 111.220 MPH
    Loading...
  12. rarest_90_DsM

    rarest_90_DsM Proven Member

    268
    3
    Joined Jul 21, 2004
    akron, Ohio
    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.
     
    My DSM:
    Loading...
  13. nightracer91

    nightracer91 Supporting Member

    363
    4
    Joined Feb 27, 2006
    Fort Wayne, Indiana
    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.
     
    My DSM:
    1993 Eagle Talon TSi AWD

    Drag Race Build

      automatic
    1991 Eagle Talon TSi AWD

    Drag Race Build

    11.783 @ 115.55 MPH
    Loading...
  14. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    3,455
    184
    Joined Aug 24, 2003
    El Paso, Texas
    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.
     
    My DSM:
    1991 Mitsubishi Eclipse GSX

    Street Build

    13.102 @ 111.220 MPH
    Loading...
  15. turbotalon31

    turbotalon31 Proven Member

    291
    3
    Joined Jan 9, 2010
    reading, Pennsylvania
    had the same issue and it was exhaust leak at the o2 housing and the downpipe.
     
    My DSM:
    Loading...
  16. nightracer91

    nightracer91 Supporting Member

    363
    4
    Joined Feb 27, 2006
    Fort Wayne, Indiana
    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.
     
    My DSM:
    1993 Eagle Talon TSi AWD

    Drag Race Build

      automatic
    1991 Eagle Talon TSi AWD

    Drag Race Build

    11.783 @ 115.55 MPH
    Loading...
    9!'clipseDOHC likes this.
  17. 9!'clipseDOHC

    9!'clipseDOHC Moderator

    3,455
    184
    Joined Aug 24, 2003
    El Paso, Texas
    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?
     
    My DSM:
    1991 Mitsubishi Eclipse GSX

    Street Build

    13.102 @ 111.220 MPH
    Loading...
  18. We're on Boost

    We're on Boost Proven Member

    751
    28
    Joined Aug 25, 2007
    Seattle area, Washington
    Here's what I did to solve that problem on my car:


    [​IMG][/URL][/IMG]


    [​IMG][/URL][/IMG]


    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.
     
    My DSM:
    1990 Eagle Talon TSi AWD

    650 whp   510 lb/ft
    Loading...
  19. nightracer91

    nightracer91 Supporting Member

    363
    4
    Joined Feb 27, 2006
    Fort Wayne, Indiana
    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.
     
    My DSM:
    1993 Eagle Talon TSi AWD

    Drag Race Build

      automatic
    1991 Eagle Talon TSi AWD

    Drag Race Build

    11.783 @ 115.55 MPH
    Loading...

Share This Page

Loading...


Log in/Register to remove ads

Support Vendors who Support the DSM Community
Ace Race Parts Advanced Fuel Injection Archer Fabrication Boostin Performance ECM Tuning Extreme Turbo Systems ExtremePSI Feal Suspension Fuel Injector Clinic Jacks Transmissions Jackson Auto Machine JNZ Tuning Magnus Motorsports Miller Import Parts Morrison Fabrication & Design OHM Racing Race Components Inc RockAuto RoadSurge Spultronix Performance STM Tuned Strictly Import Motorsports VR Speed Factory