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Catalytic Converter

In general usage the term "catalytic converter" denotes the entire system for catalytic exhaust gas cleaning in motor vehicles. It contains an effective chemical catalyst (usually precious metals such as platinum and rhodium), ceramic or metallic carrying materials, casing and various regulatory devices for controlling the process, depending on its design. Depending on its design, the catalytic converter oxidises carbon monoxide into carbon dioxide, hydrocarbons into carbon dioxide and water and/or reduces nitrogen oxides to the gases nitrogen and oxygen. Effective catalytic converters reduce the pollutants in exhaust gases by up to 90 percent. Cars use three-way catalytic converters (for petrol engines), oxidising catalytic converters, NOx storage-type converters and SCR systems (for diesel engines) - featuring up to two main and four primary converters, depending on the engine.

In order to carry out its task efficiently, the three-way catalytic converter requires a specific operating temperature. Close-coupled primary converters are therefore used that reduce pollutant emissions even while the engine is warming up.

The petrol/air mix that is most conducive to conversion is regulated by the oxygen sensor, working with the engine control unit.