AFR variance between banks. Need opinions/help. - Page 2
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  1. #16
    Senior Member Array painlessauto's Avatar
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    Ed,
    The turbo mustang is my brothers. I have a supercharged F150

    Not much room under my blower, alternator is in there. Going to loop the crossover behind the blower.
    Matt
    Last edited by painlessauto; 09-14-2018 at 10:51 AM.

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  3. #17

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    I understand, Matt. I had your ride confused with your brothers. The longer bypass hose should not hurt although short and inconspicuous is always nice.


    Ed

  4. #18
    Senior Member Array painlessauto's Avatar
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    Looking at the diagram for version B. If a balance hose was added to the deadhead of the rails wouldn't air get trapped between banks?

    I re-plumbed my rails to version B with a crossover. Bank 2 is leaner by .5 AFR until around 580 maf counts, then the banks switch and bank 1 is lean by .5 AFR throughout wot.

    Starting to question my AEM wideband o2 sensors.
    Last edited by painlessauto; 09-16-2018 at 04:30 PM.

  5. #19
    Senior Member Array painlessauto's Avatar
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    Orange line is bank 1, green bank 2

    Looking at my logs I see a trend with bank 1. Around 500 maf counts it begins to go rich, around 630 maf counts it begins to lean out. Lines cross at 11.35afr

    I bypassed my second fuel pump Hobbs switch and compared logs to rule it out.

    Starting to wonder if I should replace my wideband sensors...
    Last edited by painlessauto; 09-16-2018 at 07:09 PM.

  6. #20

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    Quote Originally Posted by painlessauto View Post
    Looking at the diagram for version B. If a balance hose was added to the deadhead of the rails wouldn't air get trapped between banks?

    I re-plumbed my rails to version B with a crossover. Bank 2 is leaner by .5 AFR until around 580 maf counts, then the banks switch and bank 1 is lean by .5 AFR throughout wot.

    Starting to question my AEM wideband o2 sensors.

    No more so than a pair of rails w/o the crossover, Matt. At first start there will be an air bubble for a very brief period of time. The start up process will flush it out of the fuel lines and it will not appear again, unless the system is disassembled — or has a leak.

    It is possible the AEM Wideband sensors are in the latter stages of their life cycle and beginning to misbehave. If they are when you source a replacement sensor I would give the NGK sensors a look. NGK's exhibit a different behavior as they approach end of life. Instead of giving close but progressively less correct readings or behaving like the AEM sensors are possibly currently doing (assuming no real AFR change is taking place), the NGK sensors just shut down. They go completely dead.

    I first discovered this working with AJ (Mofasta) on his engine. He used NGK sensors specifically for this reason. Rather than chasing a drifting sensor in it's later stages of life the NGK's just shut down completely. Another nice feature they have is the ability to accurately read down into the 0.5 to 0.6 lambda range which was important for him because he used methanol as a fuel.

    If you have good reason to believe the sensors are at the end of their lives then I would consider the NGK's as an alternative. The other thing to keep in mind is, I believe, you said this was happening in open loop. Did that mean that the AFR drift did not happen in closed loop? If that is the case, unless you have locked the ECU in open loop, does that mean the normal operation of the engine in closed loop eliminates the 0.5 AFR drift?

    If the only time the engine is seeing open loop is at start up and after warming goes to closed loop with stable AFR's you could just be chasing AFR ghosts that once warmed up disappear from the engine's operation. I know the 4.6L Terminators use an FRPS in the fuel rails to measure delta pressure across the injectors to allow the ECU to calculate the proper injector pulse width to deliver the commanded AFR. I don't know with certainty if the blown 5.4's do or not. If they do and you have disabled it in the tune or disconnected it, then the ECU can not see the pressure variations in the fuel rail and does a best guess pulse width calculation based on base system fuel pressure that was programmed into the tune.

    Because of the time delay and initial boost reference signal strength attenuation from the manifold to the regulator through the boost reference line, the actual fuel rail pressure to vary from the steady state base pressure the FPR was set to. The use of the FRPS eliminates this variable because it monitors the delta pressure in the rail in real time and delivers the information at electronic speeds to the ECU where as the FPR is reading manifold pressure changes at the much slower signal propagation speeds and attenuated signal strength present in a boost reference line.

    If the FRPS is still present and you allow the ECU to go to closed loop the AFR perturbations introduced by the plumbing should disappear and you should see two essentially similar AFR readings for both banks. Is this what happens if you allow it to go to closed loop?


    Ed
    Last edited by eschaider; 09-17-2018 at 10:11 AM. Reason: Spelling & Grammar

  7. #21
    Senior Member Array painlessauto's Avatar
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    Ed,

    You are correct. Closed loop I have no issues with afr drift. The issue is only present during open loop. My stft are spot on while driving around town. I seriously believe I've been chasing a ghost AFR signal or signals.

    My pcm does not support fuel rail pressure sensors. The factory rails had a vacuum controlled fuel pressure regulator.

    In regards to the NTK sensors... I've read online that they are not compatible with the AEM failsafe gauges. Apparently the configuration is incorrect? I wish these Bosch sensor would react the same as the NTK at the end of their life. My current sensors only have 800 miles of use "but" they were tuning miles which saw rich afr's and starts after heating them up for cold start logs. I understand that condensation will damage them if heated before firing the engine.

    The sensors are UEGO 4.2 "not" 4.9

    Do you know if there is any truck to the NTK incompatibility?

    Matt

  8. #22

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    I am not sure if the NTK sensors will work with the AEM hardware either, Matt. My best bet on that would suggest a call to AEM although they might be less cooperative than hoped for. The next best check point would be the NTK guys because they would be motivated to know everything and everywhere their sensors could be deployed.

    With a no drift outcome in closed loop the issue increasingly sounds like ghost sensor signals although it could be real variations that the ECU is correcting for once it goes closed loop. I would expect the STFT should show what is happening and if the ECU is correcting the AFR to bring it back to commanded. Your comment however about the STFT's being in tip top shape increasingly leads me to suspect some type of signal ghosting in happening in open loop.

    The most important thing is the engine is properly fueled in closed loop which it seems to be. The open loop time is essentially limited to warm up so I wouldn't be concerned about engine damage occurring. The moment the engine is up to temp you are on closed loop and the fueling issue disappears so you know the engine is safe.

    I might take some time to investigate the NTK sensor compatibility issue. BTW I just noticed I keep flip flopping back and forth between NTK and NGK naming conventions. FWIW they are the same sensor as far as I can tell. I think NTK is the more correct naming convention.

    In the FWIW bucket I recall reading somewhere that the Bosch 4.9 sensors while an upgrade to their earlier 4.2 sensors also brought some corrections in sensor operation under certain conditions. I want to say they are interchangeable IIRC however, Bosch could know for sure.


    Ed

  9. #23
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    Response from NGK/NTK

    Hello,

    *

    Thank you for your E-mail.* I don’t have a cross for the those Bosch OE numbers.* If NTK has a sensor in aftermarket that is for a Bosch wideband application,* the sensor in the NTK box is going to be a Bosch.* Our NTK wideband sensor is more resistance to contamination, but you must use a Bosch in your application to work with the AFR unit.

  10. #24

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    Well, not exactly what we were hoping for but certainly definitive in its response.

    If I were going to stick with the AEM hardware I think I would upgrade the sensors to the 4.9 units, Matt. They represent an improvement over the 4.2 generation units. Depending on costs I might consider replacing the existing AFR stuff with NTK compatible hardware if and when I decide to replace the 4.2 sensors.


    Ed

  11. #25
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    New wideband sensors netted the same results as before. Same AFR split, maybe a hair tighter. Putting my thinking cap on...

  12. #26

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    It is worthwhile remembering that the open loop operation is essentially your warm up and a few other situations, Matt. At warm up a 0.5 difference between commanded and actual AFR is not a significant event. As long as the AFRs look the same under load in closed loop you are probably good to go. The difference in temp rise during the warm up phase is for all intents and purposes inconsequential. Once warmed up and under load it is a different story and that story, for your engine, sounds like it is OK.


    Ed

  13. #27
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    What's killing me Ed is the fact that something changed a month ago, around 8-18.

    Below are two afr logs.
    Top log is from 8-8 and bottom log is from last night.

    Orange FireWire is bank 2.

    TPS counts were adjusted on 8-11. That is the only change that was done prior to the issue surfacing on 8-18.


    Last edited by painlessauto; 09-19-2018 at 10:44 AM.

  14. #28

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    Like yourself, I am running out of ideas as to what is causing the differences, Matt.

    I would expect any changes in TPS counts to affect the measured AFR for both banks similarly. What is the X-Axis in the top pic and what is it in your lower pic — time perhaps? Your top log is quite tight bank to bank while the bottom log is reporting the 0.52 difference in measured AFR you had commented about earlier.

    Have you checked the "Y" fitting that you use to split the fuel between the two rails for machining imperfections / inconsistencies leg to leg or burrs that may have been left behind in one of the legs after machining and not removed prior to sale? If you have the ability (two analog pressure sensors and 2 unassigned analog channels) it would be interesting to data log the fuel rail pressure in each fuel rail at the point in time that the AFR's diverge. If the pressures are similar the only other way the difference can occur is differing injector pulse widths being sent to the two different cylinder banks — which begs the pregnant question, why?

    The first and easiest check point would be the "Y" fitting for uniformity leg to leg. Apologies, I wish I had more.


    Ed

  15. #29
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    Ed,

    X axis is time, correct. I have two 6an feeds coming your of my hat to a billet y-block. The y block has a 8an exit which runs to my filter and up to the engine.

    I am reluctant to spend the $ to test rail pressure between banks as the AFR split was a non-issue as of a month ago. Prior to the spilt issue, my fuel system was nowhere near as balanced as it is now.

    I am smoking my exhaust and intake tonight. We'll see what I find. Hopefully a leak somewhere. The one time in my life I want to find something bad haha.

    Matt

  16. #30

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    I understand the reluctance to spend on one time instrumentation, Matt.

    While I am hopeful of an easy bad guy identification, like a pinhole exhaust leak, I am suspicious that it doesn't exist because of the consistentlbank to bank fueling you get in closed loop. It is rather amazing how uncooperative these things can be when we are actively looking for whoopses ...

    I hope you find a leak but increasingly I am thinking there is likely none, which brings us back to the pregnant why and what questions.


    Ed

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