Emission Control Systems: Description and Operation

EMISSION CONTROL SYSTEM
The emission system controls tailpipe emissions, hydrocarbons produced by evaporating fuel, and combustion gases that escape through the crankcase into the atmosphere. Effective control of vehicle emissions is necessary to reduce the automobile's impact on environmental pollution.

FUEL INJECTION
The primary emission control is fuel injection. Fuel injection offers precise fuel control over a wide range of conditions. Feedback supplied by the exhaust gas oxygen sensor and various engine sensors allows the injection system to compensate for changes in atmospheric conditions (temperature, altitude, etc.) as well as mechanical conditions (such as state of tune, etc.).

CATALYTIC CONVERTOR
The catalytic convertor effectively changes harmful pollutants into carbon dioxide and water.

FILL PIPE RESTRICTOR
To prevent the introduction of leaded fuel to the system, a fillpipe restrictor is installed. This prevents the larger diameter fuel nozzles used for leaded fuels from entering the fillpipe. Leaded fuel will permanently contaminate the oxygen sensor, and the catalytic converter.

POSITIVE CRANKCASE VENTILATION
The PCV system prevents blowby (emissions produced by the engine combustion chambers which escape into the crankcase) from entering the atmosphere. By recirculating the gases back into the intake system, blowby gases are burnt along with the incoming air fuel mixture.

EVAPORATIVE CONTROL SYSTEM
The emissions created by the evaporation of raw fuel is controlled by the use of a closed ventilation system for the fuel tank, and a canister filled with activated charcoal to capture the fuel vapors. The charcoal canister captures and stores the vapors as they expand. When the engine is started, a valve is opened allowing the engine to draw air through the charcoal canister thereby also drawing in and burning the stored fuel vapors.

EXHAUST GAS RECIRCULATION SYSTEM
The EGR system aims at reduction of NOx by lowering combustion chamber temperature through recirculation of a part of exhaust gas into cylinders via the collector chamber.