Emittersystemet

Emittersystemet, commonly referred to in English as the emissions control system, is a collective term used in automotive engineering to describe the devices and subsystems that limit pollutants released from an internal combustion engine (ICE) or other combustion sources. The system aims to reduce emissions of carbon monoxide, hydrocarbons, and nitrogen oxides, and, in diesel engines, particulate matter.

A typical emittersystemet includes catalytic converters (for gasoline engines), a diesel oxidation catalyst, a diesel particulate filter, and selective catalytic reduction systems for NOx. It also includes exhaust gas recirculation (EGR) to lower combustion temperatures, oxygen sensors and NOx sensors that monitor chemical species, and related control electronics. In modern vehicles these components are integrated with the engine control unit (ECU) and onboard diagnostics (OBD).

Operation involves converting or trapping pollutants using catalysts, trapping soot in the diesel particulate filter, regenerating the filter at high temperatures, and reducing NOx through SCR or engine adjustments. Sensors monitor performance, and the ECU adjusts the air–fuel ratio, ignition timing, and exhaust flow to maintain compliance with emission standards.

Regulatory standards such as the European Union's Euro standards and other national programs specify emission limits. Onboard diagnostics monitor performance, and maintenance—such as replacing a degraded catalytic converter, regenerating or cleaning a diesel particulate filter, or replacing sensors—helps ensure compliance. With growing electrification, the role of emittersystemet in new vehicles may decline, but combustion-based powertrains continue to rely on these systems in many markets.