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  • How do I set up closed loop lambda control

    A quick guide on how to setup closed loop lambda control with Autronic SM4:

    Light load stoic and Heavy load stoic sets what voltages on the lambda input that correspond to Lambda1, also called "Stochiometric mix".

    A narrowband lambda sensor is in a high degree affected by pressure, temperature and gas flow, which implies that one has to regulate to different voltages on high respectively low load.

    Nominal voltage for Lambda1 is 455 milliVolts for a narrowband sensor, but due to different factors one has to regulate to, for example, 498 milliVolts on light load, and to 449 milliVolts on high load.

    CLC load threshold sets at which LOAD the SM4 switches between the two values Light load stoic and Heavy load stoic.

    For closed loop lambda control to manage the emissions requirements for MOT one often only need to regulate lambda on light LOAD, and can therefore assume Heavy load stoic to be of the same value as Light load stoic.

    Start with a calibration where the base fuel table is calibrated to Lambda1 with a good wideband lambda sensor to an accuracy of at least 1% at idle, and in case there is requirements for mearuring Lambda1 correction at, for example, 2500 rpm it should be calibrated with equal accuracy there. Normally the measurement of exhaust emissions are done at unloaded idle rpm's and at unloaded 2500 rpm's.

    Set CLC load threshold to a LOAD that is a bit higher than the LOAd at which the engine idles, and then setup the lambda control to work with the sensor that will be used for Closed Loop Lambda Control. In most cases this is a narrowband sensor.

    CLC sensor direction
    specifies if a richer mix corresponds to a higher or lower voltage on the lambda input.
    For a narrowband sensor, a richer mix corresponds to a higher voltage. But for a wideband sensor a richer mix most often corresponds to a lower voltage.

    So, for a narrowband sensor one sets CLC sensor direction to Reversed, and for a wideband sensor one sets the parameter CLC sensor direction to Normal.

    An example of reasonable start values for the lambda closed loop control can be seen in the following picture:



    What principally differs between lambda control with a narrowband sensor and with a wideband sensor is that CLC adaption gain mmust be adapted to the voltage swing on the lambda input, which is much higher for a narrowband sensor than for a wideband sensor. And that CLC sensor direction must be changed. (Se above).

    CLC prop. step, CLC FB min limit and CLC FB max limit are setup values for the adaptive part of the lambda closed loop control.
    Normally one can set theese parameters to the values displayed in the picture above.

    CLC adaption lean and CLC adaption rich sets how much the lambda closed loop control is allowed to adapt the amount of fuelling from the base fuel table to achieve lambda1 on the cells that according to the AF-table shall have the stochiometric fuel mix, specified in the menu choice M1 / Base settings / Stoic AF ratio.

    Set the parameters CLC adaption lean and CLC adaption rich to -3.0% and 3.0% respectively.

    Stoic AF ratio is often set to 14.7, (AF petrol). Better results can be achieved by instead setting Stoic AF ratio to the value 14.6, because the equilibrium is 14.65 and that it is easier to regulate Lambda1 with a small amount of enrichment.

    When lambda regulating to meet exhaust emissions requirements it is beneficial to take account for that a slightly richer mix than stochiometric at the engine, (depending on after combustion effects in the exhaust system), will correspond to a mix closer to stochiometric at the end of the exhaust system. And that a slightly leaner mix than stochiometric at the engine often corresponds to a measured value at the end of the exhaust system that fluktuates between stochiometric and a leaner mix.

    By setting CLC mode to ECU internal C/L The closed loop lambda control is activated with the chosen settings. Save the settings into the SM4 and stop the engine and then restart it. Now the CLC function learns dynamically how much it has to adapt the base fuel table to keep Lambda1 regulated. It stores the adaption values in an internal table that is entirely handled by the Closed loop Lambda Control function.
    Attached Files
    Johan Jansson, +46-708-280832

  • #2
    GREAT write up!!! Thanks

    I have been looking to use the closed loop feature and this helps quite a bit. I do have a few questions if you don't mind.

    Can you explain in greater detail what the CLC prop step and CLC FB min/max limit steps do?

    I will be using this with a WB 02. After rereading this I think I have to lower the CLC adaption gain as the WB voltage is much higher in my case, 4.0714V at 14.7:1.

    When I would turn on the CLC my 02 would be very erratic like it would keep overshooting the target back and forth.

    Thanks

    Comment


    • #3
      Can I set it up to come out of closed loop at a certain load?
      It seemed that when I went WOT the closed loop fuel addition continued and made me run super rich at WOT.

      I want to come out of closed loop at 60% load and run strictly off the fuel tables.

      Possible?

      Also, I have the 1.06 firmware on my SM4 and I have my rev limiter setup as a fuel cut. Will I have to change my rev limiter with the CLC enabled?

      Comment


      • #4
        Originally posted by Wicked View Post
        Can I set it up to come out of closed loop at a certain load?
        It seemed that when I went WOT the closed loop fuel addition continued and made me run super rich at WOT.

        I want to come out of closed loop at 60% load and run strictly off the fuel tables.

        Possible?
        The CLC only operate at loads where the AF table specifies stochiometric AF. And you should preferrably not run stochiometric at WOT.

        Originally posted by Wicked View Post
        Also, I have the 1.06 firmware on my SM4 and I have my rev limiter setup as a fuel cut. Will I have to change my rev limiter with the CLC enabled?
        Why should you need to change the revlimiter because you run CLC? Strange question.
        Johan Jansson, +46-708-280832

        Comment


        • #5
          Originally posted by underpsi68 View Post
          Can you explain in greater detail what the CLC prop step and CLC FB min/max limit steps do?

          Thanks
          Can anyone help with this?

          Comment


          • #6
            Originally posted by Wroom View Post
            The CLC only operate at loads where the AF table specifies stochiometric AF. And you should preferrably not run stochiometric at WOT.


            Why should you need to change the revlimiter because you run CLC? Strange question.
            I don't think its a strange question.

            From the software...."NOTE: When CLC enable on firmwares 1.01..1.06, fuel cut cannot be used as power reduction.

            Comment


            • #7
              Wroom, you say that:

              So, for a narrowband sensor one sets CLC sensor direction to Reversed, and for a wideband sensor one sets the parameter CLC sensor direction to Normal.
              I'm bit confused. If I use wideband with the "standard" scale 0V=10AFR and 5V=30AFR, shouldn't I use then REVERSED scale?

              Ecu software atleast says:

              Normal (0V=Lean;5V=Rich)
              Via Autronic A/F ratio meter.
              Reversed (5V=Lean;0V=Rich)
              Direct to 02 sensor.

              Comment


              • #8
                Originally posted by yrkesman View Post
                Wroom, you say that:
                Originally posted by wroom
                So, for a narrowband sensor one sets CLC sensor direction to Reversed, and for a wideband sensor one sets the parameter CLC sensor direction to Normal.
                I'm bit confused. If I use wideband with the "standard" scale 0V=10AFR and 5V=30AFR, shouldn't I use then REVERSED scale?

                Ecu software atleast says:

                Normal (0V=Lean;5V=Rich)
                Via Autronic A/F ratio meter.
                Reversed (5V=Lean;0V=Rich)
                Direct to 02 sensor.
                The help text in the cal software seem to be wrong.

                I guess that bit of help text has been with us for quite some time now. I haven't reflected over the help text, since i know by heart how it is and never had to look.

                Connecting a lambda sensor directly to the ECU will show lean AFR when the O2 input voltage is 0 Volts.
                A wideband sensor with a linearized output (normally) gives out 0 Volts for a rich AFR.

                Originally posted by wroom
                So, for a narrowband sensor one sets CLC sensor direction to Reversed, and for a wideband sensor one sets the parameter CLC sensor direction to Normal.
                Johan Jansson, +46-708-280832

                Comment


                • #9
                  I am trying to setup CLS, and have few questions/issues

                  After reading all threads on CLS, I followed the general advice of setting my WBO2 (Techedge 2COB) to output 0-5v with range of 10-20AFR, in my SM4 I setup Span to 5000 and Offset to 1000 - I have then confirmed these settings making sure both Techedge and SM4 are reading the same

                  I also set stoich to 14.6 as Wroom suggested in the OP

                  Then I locked Techedge in 14.6 to see the voltage (2.3 volts) and put it for both light and heavy load stoich

                  My base fuel table is tuned in the load load area where I call for 14.6, I confirmed it by autologging and driving around
                  Tried on idle - the second I activate CLS, it starts operating within the max limit of CLS adaptation rich and my AFR goes rich.... if I increase CLS adaptation rich to 10, it will go to 10 and make AFR more rich

                  I seem to have done everything by the book, what is causing this effect?

                  Attaching both cal and log
                  Attached Files

                  Comment


                  • #10
                    For some reason I can not down load the Cal.

                    Under the CLC settings, do you have it set with a negative number? Don't ask me how I know this. LOL

                    Comment


                    • #11
                      perhaps this may help

                      Comment

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