Audi 80 Quiz
MPI and MPFI Injection Systems

Lambda Control

In this manual: MPI and MPFI Injection Systems
Technical Description — 39Engines — 41Exhaust System — 13Cooling System — 28Fuel tank and fuel pump — 12Air Filter and Intake Ducts — 13Mono-Motronic Injection System — 18Digifant Injection System — 19KE-III-Jetronic Injection System — 35MPI and MPFI Injection Systems — 32Clutch — 11Transmission and Driveline — 21Suspension and Steering — 33Brake System — 41Anti-lock brake system — 8Wheels and Tires — 13Body Electrical System — 35Ignition System — 24Lighting — 14Signaling Devices — 7Instruments and Auxiliary Equipment — 54Heating and Ventilation — 7Body Components — 18Troubleshooting — 6Specifications — 13
~1min read

The catalytic converter can only work correctly 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, MPI/MPFI injection systems are equipped with so-called lambda control. The lambda sensor measures the oxygen content in the exhaust gases, a value comparable to the air/fuel mixture composition. If the value deviates from the ideal, the control unit corrects the mixture composition.


Control operates in the range from λ = 0.8 to λ = 1.2, and fluctuations of this value are desirable, because only in this case does the catalytic converter achieve almost complete conversion of harmful substances.


The lambda sensor only sends a signal above temperatures of 350°C. To reach this temperature range as quickly as possible, the sensor is electrically heated. Until the sensor reaches its operating temperature, the system remains uncontrolled and is based on a preset average value.


As you may have guessed: the 6-cylinder Audi is equipped with two catalytic converters and also two lambda sensors.

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