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Link G4 Plus Software Tutorial: Closed Loop Lambda Control

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Closed Loop Lambda Control

03.10

00:00 - The closed loop lambda function allows the G4+ to take input from a lambda sensor and automatically make adjustments to the fuel delivery to meet a target.
00:09 This can help keep your air/fuel ratio more consistent across varying atmospheric conditions, improving fuel economy and reducing emissions.
00:18 The closed loop lambda function can be accessed by opening the ECU settings menu and clicking on fuel and then closed loop lambda.
00:26 By default, this function is disabled so you will need to set it up to suit.
00:31 First we need to select the lambda mode and this will depend on the type of sensor you're using.
00:36 Stoich narrowband will suit narrowband sensors that are only accurate around the stoichiometric air/fuel ratio while stoich wideband will work with wideband sensor controllers.
00:48 If you're using a narrowband sensor, the closed loop lambda control can only correct the AFR to stoichiometric which is only useful for cruise and light load situations.
00:58 A wideband sensor on the other hand will allow full control and the ECU will attempt to match the values entered into the AFR lambda target table.
01:07 We will look at setting up the wideband mode so we can select this option.
01:12 We now have a number of parameters that need to be configured.
01:15 First we have ECT lockout which prevents the ECU going into lambda control below a certain temperature.
01:22 This ensures the closed loop control isn't active during warmup enrichment.
01:27 The next option is the timer lockout.
01:29 This prevents closed loop control for a certain length of time after startup.
01:34 This gives the sensor time to start working and gives the engine time for any post start enrichment to decay.
01:40 We then have some parameters that allow us to define when the closed loop lambda control will be active.
01:45 These are RPM high, RPM low and MAP lockout.
01:50 The lambda control will only be active when the engine is operating between the RPM high and low lockouts and below the MAP lockout.
01:57 Normally closed loop lambda control is used to control the AFR during cruise and light load so these parameters need to be adjusted to suit your requirements.
02:07 Next we have the fuel trim limit which limits the amount of control the ECU has over the fuel trim.
02:13 Closed loop lambda control is not a substitute for proper tuning and the ECU should not need to make large changes.
02:20 Lastly we have the gain control which defines how aggressively the ECU will chase the target.
02:27 This needs to be adjusted until the ECU matches our target quickly without overshooting and oscillating wildly.
02:33 You can watch the closed loop control in the run time values screen under fuel trims.
02:37 This can help you tune the gain but normally a value of two to three works well.
02:44 Since we are using a wideband sensor, it's important to makes sure that the AFR lambda target table is set to what we want the engine to run.
02:52 This is the table the ECU will reference to make changes so it needs to be set properly.