The Closed Loop Lambda driver allows the use of a standard 0-1v oxygen sensor to help maintain stoichiometry during areas where the AFR (Air Fuel Ratio) target table is set to 14.7.


This is particularly useful for conditions such as ‘fast-idle’ for emissions compliance (as used by the UK VOSA IVA and MOT scheme). With correctly functioning closed loop NB lambda control, when the ECU is commanding a 14.7 AFR, the narrowband sensor should allow the engine to reach it. That being said, for WOT and ‘lean cruise’, a narrowband should not be used to ascertain the engines AFR, as it is accurate only around 14.7AFR (lambda 1.0). More info on this is here.


For continuous closed loop AFR correction for any AFR, please refer to sections on Wideband Lambda control. Either using an external wideband controller (with the ME221) or the Internal controller as built in to the ME442 range.


The driver can be found under ‘Lambda Control->Lambda Settings’. When opened in MEITE, and the "Type" is set to Narrowband, the following options and settings are presented:

The settings shown are typical of a standard Narrowband sensor on a normal, 4 cylinder naturally aspirated engine. Details of what each field represents are below.


NB Stoich (V)
This is the voltage the control system should target for stoichiometric fuelling - typically around 0.5 volts - this can be checked with your sensors datasheet.


NB Acceptable Stoich
This is the allowed error in Volts at which the algorithm will consider the mixture to not need adjusting.


NB Sensor Fault
This is the voltage at which a fault of the sensor will be considered, and the algorithm will not operate in this case.

NB Engine Rotations
This is the amount of time (in engine rotations) that are allowed to pass before applying the next ‘step’.


NB Step Size
This is the step size in percent by which the algorithm will alter the fuelling (either increasing or decreasing) every ‘step’ until it hits the right NB Stoich voltage received from the sensor.


Authority (%)
This is the maximum the algorithm will be allowed to modify the maps fuelling by to try to reach stoich. If it needs to move more than this than the map is most likely incorrect.


RPM Min
The minimum RPM before the algorithm will operate.


TPS max
The maximum throttle percent before the algorithm is turned off - i.e. to avoid trimming the map at (rich) wide open throttle positions.


MAP Min/MAP Max
The zone in KPa reported from the MAP sensor where the algorithm will operate.


Coolant Min
The coolant temperature in degrees before the algorithm will operate. (i.e. until the engine is above 65*C)


Target AFR Trigger
One of the more powerful aspects of the ME ECU - the algorithm will look at your Target AFR table and only try to trim the fuel when your target is as specified, generally, 14.7 (that is the only value a NB sensor can indicate cleanly). This stops it trying to tune in the intentionally richer or leaner areas of the map.