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Thread: GPEC2A changing stoich value does what?

  1. #1
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    GPEC2A changing stoich value does what?

    no one will ever find this in that srv thread

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    Quote Originally Posted by LilSick View Post
    no one will ever find this in that srv thread
    I agree, there is a ton useful information here also.
    I feel like no matter what stoich is set to, on narrow band vehicles, it's going to trim to 14.7 with gas. I can and have been wrong many times. As I understand narrow bands run 0-1v, so changing stoich (my thought) is that it would basically change the ve calculation and my trims would be off. Tune ve and it's back at 14.7 target. Or in pe it would run richer than target (I target about 12.2 afr). So tune pe and it's all back where we started.

    Maybe it's different with wideband cars.. I wonder if that's where the confusion comes from. Maybe I'm wrong. I am still learning.. But ultimately I'd like to know if changing stoich would actually change anything and benefit me any..

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    Quote Originally Posted by spoolboy View Post
    Regarding stoich settings - that is the initial target for the "math" in the PCM. It will still drive to the narrow-band voltage for stoich and just cause a wider variation in fuel trims to get there.

    For example, if you change the stoich setting for more fuel, you will just have larger negative fuel trims. You will not change what the narrow band sensors can read. The Hellcat uses wide band sensors, so it may be different.
    "It will still drive to the narrow-band voltage for stoich"???

    what is IT and what voltage is that?
    Last edited by LilSick; 05-30-2023 at 11:41 AM.

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    thanks for the article

    i saw one explaining lambda and the pump wide bands use i will find and post

    still dont know what you mean by IT

    or why 4 wire sensor that has 0-5v output is being called narrow band

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    Quote Originally Posted by LilSick View Post
    thanks for the article

    i saw one explaining lambda and the pump wide bands use i will find and post

    still dont know what you mean by IT

    or why 4 wire sensor that has 0-5v output is being called narrow band
    I'm fairly certain the narrow band o2 sensor uses a 0-1v signal. I don't know which cars use a wideband but fairly certain trucks use narrow band.
    Please correct me if I'm wrong but a narrow band will switch between above and below .5 volt to determine stoich.
    I will look at a log in a second and see what the voltage reading is on my o2s to be sure

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    lets not talk about how a narrow band sensor works

    that is in the article SB posted above

    lets talk about what all is actually effected by changing the value in the tune (stoich)

    5.30.png

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    *the 4 wire sensors in my scat are not narrow band

    5.30 wide band.png

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    5.30 wide band0.5.png

    that log ^^^ is from my scat, not a hellcat (3.3v)

    so... changing the value in the pcm... does it change the mixture at idle or not?

    you had said the trims will be further off but that doesnt make sense

    can you explain your theory?

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    you know i woulda already if my car were together right now

    if its not changing the mixture OR what the sensors call good, what does that value do?

    its a variable... what does it vary??

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    Changing stoichiometric in the tune affects airflow calculations. No different than changing fuel injector flow rate. Because of the way a narrowband functions, they will always try to maintain a physical stoichiometric ratio in closed loop no matter what fuel is used.

    An example where changing stoichiometric is useful is going from regular gas to some blend of ethanol. E30 you'd set 12.96, and that way airflow wouldn't have to be re-tuned. All you have to do to understand this is look at a FlexFuel tune. There's a range of stoichiometric ratios on the fueling side but no range for airflow tables.

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    Quote Originally Posted by SiriusC1024 View Post
    Because of the way a narrowband functions, they will always try to maintain a physical stoichiometric ratio in closed loop no matter what fuel is used.
    and the 392 uses 0-1v narrowband sensors?

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    same thing

    just calculations. none of it is real. i mean the engine is a pump, that is real. but think about ve

    changing ve calculations changes fueling

    cant change the actual airflow

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    Changing stoich will just skew the fuel trims during closed loop but the vehicle will always target lambda 1.0 using the narrowband O2 sensors.
    However, once it's in open loop, then the stoich change will affect the actual lambda/AFR because it does not rely on O2 feedback here.

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    Im not sure what you mean,
    but changing the stoich in the pcm does nothing at closed loop, because ANN will do this, as long as it is activated.
    WB are only used by Hells.

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    can you make a narrow band car run on wideband?

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    not without changing the os and who knows what in the controller

    maybe start a separate thread on the subject?

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    Quote Originally Posted by CHARLZ1FORD View Post
    can you make a narrow band car run on wideband?
    No. Why would you want to? The accuracy of a wideband decreases over time. Some Fords use widebands, but they are double checked for error with narrowbands through FAOSC.

    If you want goofy non-stoich fueling full time then you'll have to run open loop.

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    Quote Originally Posted by SiriusC1024 View Post
    No. Why would you want to? The accuracy of a wideband decreases over time. Some Fords use widebands, but they are double checked for error with narrowbands through FAOSC.

    If you want goofy non-stoich fueling full time then you'll have to run open loop.
    if that is the case then why run it in the hellcat that has the same gpec2a
    im doing my best to post photos of the wiring but it insists on not uploading the photos but the only difference to the wiring is an extra 4 wires.
    main reason i would like to run it is to make the car actually run the afr i commanded.
    Last edited by CHARLZ1FORD; 06-03-2023 at 08:33 PM.

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    Right. Again, why would you want to run anything other than stoichiometric? Lean cruise maybe? Being able to tightly control fueling to maintain stoichiometric ratio is a big part of why modern engines have the efficiency and longevity they do. Might as well run a carburetor if that doesn't mean anything to you.

    Using a wideband full-time, like in the Hellcat, gives the advantage of precise fueling during power enrichment. As far as PE, there are things called rich-best-torque and rich-best-power. The wideband is able to compensate for environmental conditions and fuel mixtures to maintain FAR during PE. This maximizes engine power and engine safety. With narrowbands the tuner sets PE, but it's simply open loop.