Audi Glossary

The exhaust emission control system converts the pollutants created during the combustion process into substances more compatible with the environment. The central element in the car’s exhaust emission control system is the catalytic converter. An oxygen sensor or lambda probe measures the residual oxygen in the exhaust gas and adjusts the engine’s fuel-air mixture to the correct ratio. Powerful engines often have up to four pre-converters and two main converters. For diesel cars, a soot filter may also be a part of the emission control system.