The proper functioning of any engine rests on having the correct Air-Fuel Ratio (AFR). As the name suggests, it's the ratio between the air's mass and the fuel's mass that's being burned in the cylinder. There are some key terms here:

Stoichiometry = the ratio at which all the fuel is burned (14.7 for pump gasoline)

Lean mixture = more air than fuel (>14.7)

Rich mixture = more fuel than air (<14.7)

Lambda reading = Current AFR / Stoichiometric AFR

Note that the Air Fuel Ratio the engine requires in order to operate at maximum power and reliability changes depending on your engine, load and RPM. Basemaps are provided with a reasonable AFR table but may not be perfectly suited to your specific engine configuration - consult with your chosen tuner/engine-builder for the best AFR table for your build.

By defining the desired AFR for specific conditions (normally a 2D table against RPM and Load) and by using a wideband sensor to measure the actual AFR, we can make real-time corrections as to how much fuel is being injected in order to reach the desired AFR. In short, if the current AFR is smaller than the target AFR, then it means the mixture is too rich and we need to make the injection pulses shorter. Similarly, if the current AFR is bigger than the target AFR, this suggests we are running too lean and more fuel needs to be added.

The “Long Term Trim” uses those real-time corrections and compounds them over time. As more real-time trim values are gathered and stored, the initial fuelling values as the engine enters a set of conditions (RPM and Load) become more precise and in need of fewer corrections from the wideband sensor.

Lambda control relates to using a sensor to measure the exhaust gasses and used to either monitor it during the tuning stage, or, apply real time feedback to adjust for fuelling errors. The default layout of the lambda tab is shown below.


The Lambda Settings driver allows the use of a narrowband or wideband lambda sensor for fuelling corrections. Note that an accurately tuned calibration accounting for all conditions does not need lambda feedback. Lambda feedback aids in emissions. The only issue being an exhaust leak (more air) could be corrected by lambda feedback making the engine richer. Because of this the authority percentage (see below) limits the amount external feedback can effect it. Use the default "Lambda" page to have everything you need visible.


You can enable lambda control by using either using a basic narrowband sensor, an external wideband controller (with the ME221) or the Internal controller as built in to the ME442 range.


Be sure to set your target AFR table to the values you would like.


The driver can be found under ‘Lambda Control->Lambda Settings’. When opened in MEITE, and the "Type" is set to either external (on ME221) or usually "Internal" on the ME442, the following options and settings are then presented:





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


Type: (Disabled, Narrowband, Wideband Prop.)

You can also turn off lambda feed back by setting this to disabled.


You can set it Narrowband mode or;


If using an accurate wideband lambda, there are two main methods of closed loop control - "simple" and "proportional". Simple simply goes max authority rich/lean depending on the engine need enrichment or en-leanment. It generally should not be used except for testing purposes. Proportional is the usual method of control. See the WB Algo P details below for more information.


Startup Delay

This is the delay after the engine starts running to wait before begging lambda control strategies. It allows for external wide bands to warm up etc.


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


RPM Min/ MAP Min, MAP Max, TPS Max

These are the constraints required for lambda control to work - if the engine is operating outside of these settings, the lambda fuel trim will revert to 0%.


TPS/MAP Max Delta

These are the maximum rates of change that will allow lambda control to happen. i.e if the Throttle is moving at ahigher rate than this TPS settings, then lambda control will be disabled until the engine is "steady state" again.


Step Size (%) and Eng. Rotations/Step

These are only used for narrowband tuning - every time the engine turns the amount of rotations set, the fuelling trim will step by the set amount in the required direction to enrich/en-lean.


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


NB Stoic (Volts)

This is the target voltage for the system to aim for from the narrowband sensor. It is usually around 0.5volts.


NB Acceptable Stoic (Volts)

This is the error that allowed either side of the NB Stoic value at which trimming stops - i.e the lambda target ash been met.


Target AFR Trigger Value (AFR)

When using a narrowband, the lambda trim will only operate when the engine is in the rea of the Inj. Target AFR table that matches this reading. i.e usually only around 14.7 is typical.


WB Sense Min/Max (V)

These are voltages below and above which the AFR wideband (external) is considered faulty, and should then be ignored, and the lambda tri set to 0%.


WB Algo. P

The "WB Algo. P" value should typically be set to 0.5. This uses the amount of error to adjust the fuel trim percent  more smoothly. A larger P means faster response, but runs the risk of overshooting. A lower P means smaller steps (so longer to get to the target) but reduces risk of overshoot/oscillations.