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Resolved Is this normal AFR reading / wideband behavior during cruise?

Posted by Kryndon, Jan 17, 2020

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  1. Kryndon

    Kryndon Proven Member

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    Joined Jan 10, 2014
    Bulgaria, Europe
    Still getting used to having a wideband O2 and gauge. I noticed that my AFRs on the gauge switch very quickly between 14.6 and 15.1 AFR during cruising at 60 mph and a mostly level surface. It measures very close to that during idle, too. I am just unsure if it's meant to do that or just stay at a constant 14.7 for example (if everything is running fine). Could a tiny air leak at the bung weld or anywhere before the O2 cause the reading to go to 15 like in my video? Or am I simply not understanding how the O2 operates? I know it's based on a 0-5 volt range but still. Please take a look just in case, sorry for the shakiness! Also just to clarify, I'm not asking if the actual AFRs are okay, but rather the constant switching on the readings.

     

    Street Build 3K  12

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  2. Vegas smith

    Vegas smith Proven Member

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    Houston, Texas
    In my experience that's perfectly normal.
     

    Street Build 3K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  3. DSMPT

    DSMPT Proven Member

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    Joined Jun 12, 2014
    Japan / Mexico, Arizona
    +1 for @Vegas smith. Doesn't look abnormal. I would be worried more if the number would constantly stay with 14.7. But yes, exhaust leak would affect the a/f number.
     
    Last edited: Jan 17, 2020

    Drag Race Build 2K  3

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

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    1998 Mitsubishi Eclipse GSX
    awd · automatic · 2G DSM
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  4. pottersgst

    pottersgst Proven Member

    51
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    Joined Oct 15, 2006
    franklinville, New Jersey
    Another +1 to being normal my plx dm6 does a similar thing however I know for a fact I have a boost leak no exhaust leak but mine happens more at idle
     

    Street Build 493  22

    1995 Mitsubishi Eclipse GSX
    awd · automatic · 2G DSM

    434  0

    1999 Mitsubishi Eclipse GST
    manual · 2G DSM
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  5. 2g2slow97

    2g2slow97 Probationary Member

    14
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    Joined Jul 23, 2019
    Princeton, Kentucky
    Mine does this, it cycles when your Front O2 does. Since you’re In closed loop at cruise/idle the fuel is adjusting constantly according to what your sensors are reading.
     

    Street Build 244  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  6. Blinkyblinx9

    Blinkyblinx9 Probationary Member

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    Joined Jan 22, 2019
    Clinton, Iowa
    I have no experience with digital gauges but always assumed that a wide-band would kind of smooth out the oscillation of your O2 so you get a steady readout. What good is a number that changes so fast that you can't see what its saying? If my analog gauge did this I would have returned it.
     

    206  1

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM
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  7. Kryndon

    Kryndon Proven Member

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    Joined Jan 10, 2014
    Bulgaria, Europe
    Thanks guys, I'm glad it's looking normal. Hopefully this year I'll finally integrate ECMlink into my car and get more use out of the wideband! (and tons more questions to follow with that, hah)

    P.S ----- Blinky I just saw you posted a message while I was writing mine. I think 2g2slow97 raises a good point. The main front O2 is running in closed loop and cycling constantly. It's impossible to have a 100% always accurate and equal air fuel ratio going into the engine and coming out, at least not with these old cars. There would be tiny differences of fuel and air particles flowing in and out, and apparently the wideband Bosch unit is so accurate and sensitive that it picks these changes up immediately as they flow through the pipes. I don't know if there's a way to adjust the wideband's controller to log the readings in longer intervals and how that would affect tuning later on.
     

    Street Build 3K  12

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  8. 2g2slow97

    2g2slow97 Probationary Member

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    Joined Jul 23, 2019
    Princeton, Kentucky
    I see this a bit using the narrow sim in link.
    It cycles the O2 at .20v to .80 with squared edges. Unlike using just an O2 it gives more Gradual drops.

    Lock your car into open loop for a moment while driving. You’ll see your wide band act differently.
     

    Street Build 244  1

    1997 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  9. tk106

    tk106 Supporting Member

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    Cincinnati, Ohio
    Only time you should see it steady is up top at wot.
     

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    2000 Jeep Cherokee Sport - Classic
    awd · automatic · Misc Vehicles

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    93 Civic 4 Door -sold-
    fwd · manual · Misc Vehicles

    Street Build 2K  6

    1992 Eagle Talon TSi AWD
    12.625 @ 111.42 · 1G DSM
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  10. curt-s

    curt-s Proven Member

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    Winterville, MB, Canada
    WBO2, especially those that are digital gauged, are meant for instantaneous readings.. an average/smoothing would delay your ability to read what your O2 is at the moment you look at the gauge or distort the actual number because it took other previous readings into account. A WBO2 has no understanding of open or closed loop operation.

    An analog gauge is different because the speed of the stepper motor. It's not as fast as a digital readout, hence you always get either delayed or "averaged" readings. Not as accurate but as long as it has a quality sensor and stepper, still usable.

    When in closed loop your ECU is always chasing the sensor's last readings to adjust for ~14.7:1 so it will oscillate. The two are never in perfect sync in CL and you blow past 14.7 and go rich or lean, then it has to backtrack. Perfectly normal. However, when it doesn't oscillate, you're likely running in open loop and it's up you to and your tune to determine whether that's correct given how you're operating the car at the time.

    A slow (old, poor quality) sensor will cause a longer oscillation period which will affect how the engine runs because of the increased length of time it's outside 14.7. If it's well off, you may notice decreased or inconsistent torque output.

    A pre-sensor leak, depending on how bad, may still allow you to oscillate around 14.7 provided you have enough space in your fuel trims +% for the ECU to adjust with extra fueling but your trims would read higher than 100%. If you have a constant high AFR on cruise in closed loop, you probably blew past the adjustment % of the ECU for extra fueling which depends on ECU. Look at your trims in that case and fix the leak.
     

    Street Build 2K  1

    1991 Eagle Talon TSi
    fwd · manual · 1G DSM
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