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Brief description

Brief description

To meet the exhaust emission requirements applicable in certain markets, the cars are equipped with one of the following exhaust emission control systems:


Crankcase ventilation

• The exhaust gases passing the pistons and piston rings must be allowed to exit the engine. If the crankcase gases are not evacuated, the pressure in the crankcase will continue to increase until something gives. The crankcase gases must not pass into the engine bay, as they contain large amounts of unburnt hydrocarbons. To evacuate the gases, there is a system that recycles the hydrocarbons and keeps down the pressure in the crankcase. See Crankcase ventilation .



Three way catalytic converter

• To reduce the amount of harmful exhaust gases, the car is equipped with a three-way catalytic converter. The engine's exhaust gases pass through the catalytic converter where the catalytic material starts a chemical process. Provided that the closed loop fuel injection system maintains the fuel-air mixture at an optimum level, the catalytic converter reduces nitrous oxides (NO x ) and oxidizes carbon monoxide (CO) and hydrocarbons (HC). The end products are carbon dioxide (CO 2 ), water (H 2 O) and nitrogen (N 2 ).

The catalytic converter can reduce emissions provided the fuel is unleaded, since lead destroys the active components in the catalytic converter.

See Closed loop fuel injection system .



Closed-loop fuel injection system

• The catalytic converter has a high conversion ratio within a very narrow range. If the fuel-air mixture is not kept within this range, one or more gases will exceed permitted limits. A closed loop fuel injection system guarantees a correct fuel-air mixture. The level of oxygen is measured by an oxygen sensor that informs the Trionic or Motronic engine control module. The control module governs the fuel injection pulses so ensure the correct fuel-air mixture. See Closed loop fuel injection system .



Evaporative emission system

• Hydrocarbons that evaporate in the fuel tank are passed through a pipe to a container filled with active carbon (EVAP canister) and is stored in the active carbon while the car is stationary. The fuel vapour is then drawn into the engine and is burnt together with the ordinary fuel mixture when the car is driven. See Evaporative emission system .



Deceleration device

• The deceleration device (not B235R) prevents emissions of unburnt hydrocarbons during engine braking and is integrated in the IAC valve. See Deceleration Device .