Lambda Control

Lambda sensor connector pins:
1 – lambda sensor heater;
2 – lambda sensor signal.

The catalytic converter can operate correctly only if the excess air factor λ is as close as possible to 1, which corresponds to an air-fuel ratio of 14.7:1. To achieve this in practice, the KE-III-Jetronic injection system is equipped with so-called lambda control.

The lambda sensor measures the oxygen content in the exhaust gas, which is a reference value for the air-fuel mixture composition. If the value deviates from the ideal, the control unit instructs the pressure regulator in the mixture control unit to immediately change the mixture composition. Control operates (oscillating around the target, because only in this way can the catalytic converter achieve almost complete conversion of harmful substances) in the range from λ = 0.8 to λ = 1.2.

The lambda sensor sends a signal only at temperatures above 350°C, so it is electrically heated (in addition to exhaust gas heat). Until it reaches its operating temperature, the system remains uncontrolled and is based on a preset average value. Control is likewise suspended when mixture enrichment is activated at full load.