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Unmodify lambda control for normal operation

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  • #16
    Originally posted by -ice- View Post
    Anyway I would like to know more about the long term fuel trim.

    As a two point Lambda probe can only measure rich or lean the ECU can easily correct the fuel to reach lambda 1 (just at the point the probe voltage is jumping)
    But for long term trim it must be different. I think it works the way the ECU notes how long it needs to adjust fuel to reach lambda 1. With this it could know if the engine ran just a bit rich/lean or if it ran mega rich/lean.
    Usually the adaptive values will be stored in the Xram to keep them stored until the battery voltage is disconnected. At the moment I don't know if the long term correction is just a single value which will be applied to all running conditions of the engine or if it is more advanced, somehow like a dynamic map to correct different in different running conditions.

    who knows more?

    Daniel
    Ask and you shall receive -ice-. here is all of the lambda control info from the function sheets.
    Attached Files
    "The really good drivers got the bugs on the side windows." Walter Röhrl

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    • #17
      just an update on this issue. i replaced my ebay injectors with fuel injector development 630cc injectors and the problem is resolved. i have way better control over these injectors now. i guess i can say the ebay injectors are not good at all and are highly suggested to avoid them at all costs.
      "The really good drivers got the bugs on the side windows." Walter Röhrl

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      • #18
        Hi,

        if someone is interested in this adaptive function, he may read the European Patent: EP0142011

        f.e. to find on epo.org when search for „patents“. Look at full version not abstract. It‘s in german but it explains it all :-)

        Best Regards

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        • #19
          With that patent you find a lot of other about functions we have

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          • #20
            To explain a bit the lambda learning:

            In general we have an outer PI control to do the shortterm fuel adjustment. As you know the lambda control is not always active and activated by some thresholds like the progammed load curve for activation.
            In the inside of this control loop there are the adaptive learning control loops. These are „just“ integrators with time constants in minute areas. These regulators adjust the injection amount over time in a way of multiplicative and additiv correction. But this learning process is not always active. It depends f.e. on rpm, and airmass which integrator is actually learning at the moment. The overall goal of this internal integrators is to keep the outer PI controler in a symmetric neutral state (which means Pi regulator output 1), so it can regulate the shortearm lambdadrift very fast and without big overshooting, even if the engine has aged or some small airleak problems are present. I call it cascade control...it‘s a control loop inside of control loop.
            The interesting thing is the fuel trim values are stored „permanently“ in XRAM and will according to my actual knowledge also be used, if lambda is not active at the moment. This has some consequence for using the prjmod. As I remember it has adaptive learning disabled, but if there are still old learned values in the Xram, this could affect the actual injection time. So when using PRJmod it‘s wise to reset the XRAM one time by unplugging/plug the battery power to the ecu.
            if you want to learn more look at that patent Fig. 3.

            byebye
            Last edited by -ice-; 21 February 2018, 15:33.

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            • #21
              The learned value at stock motronic is always in "use" - when you have faulty lambda sensor and high fuel consumption it's not enough to unplug the lambda sensor, also a reset is needed.

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              • #22
                Japp, i juest guess with disconnected lambda probe the adaptive learning will not become active again. So it will keep and use the old integrator outputs stored in XRAM.

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                • #23
                  You need to remove all power from ECU and also disconnect emulator (so it does not power XRAM), then XRAM contents are lost.
                  Or like I did, you can set the upper and lower limit to 0
                  http://tuner.ee - http://www.facebook.com/tuner.ee

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