RhinoPower Ltd

Air-Fuel Equivalence Ratio - this can be output via an OBD2 PID.

Air-Fuel equivalence ratio, λ, is the ratio of actual AFR to stoichiometry for a given mixture. λ= 1.0 is at stoichiometry, rich mixtures λ < 1.0, and lean mixtures λ > 1.0.

There is a direct relationship between λ and AFR. To calculate AFR from a given λ, multiply the measured λ by the stoichiometric AFR for that fuel. Alternatively, to recover λ from an AFR, divide AFR by the stoichiometric AFR for that fuel. This last equation is often used as the definition of λ:

Because the composition of common fuels varies seasonally, and because many modern vehicles can handle different fuels, when tuning, it makes more sense to talk about λ values rather than AFR.

Most practical AFR devices actually measure the amount of residual oxygen (for lean mixes) or unburnt hydrocarbons (for rich mixtures) in the exhaust gas as know in PPCHS.

PID 0124 is the lambda reading/commanded lambda for O2S1

The term "wideband O2 controller" is a bit of a misnomer - in that the device does not control the O2 in any way - think of it as a "wideband O2 sensor controller".

Narrow band O2 sensors are less expensive than wideband and as a result much more common, but, because of their narrow range they provide less information to the ECU, which is not normally a problem on a standard or unmodified engine, because the mixture requirements are reasonably well established.

On a modified engine, especially one that is being setup for the first time, the tuner will have only a rough idea as to where the mixture settings should be - a narrow band O2 sensor in this application will only tell him lean or rich, but not how lean or how rich, wheras a wide band sensor will provide that information.

What the wideband O2 controller does is provide the control circuitry required to drive the sensor itself - and will usually have an output to drive a display and an interface to a narrow band input on an ECU.