Emission Control Systems: Description and Operation

EXHAUST EMISSION CONTROL SYSTEM DESCRIPTION

Exhaust Gas Recirculation (EGR) System

Injects a metered amount of exhaust gas into the intake manifold, lowering peak combustion temperatures. Lowering peak combustion temperatures inhibits the production of NOx. (Production of Oxides of Nitrogen (NOx) is greatest at combustion temperatures over 2300° F.)

Air Injection System

Adds air to burning exhaust gases in the catalytic converter, aiding the oxidation of Carbon Monoxide (CO) and Hydrocarbons (HC), this creates additional heat, (which further accelerates catalytic converter operation).

Catalytic Converter

Changes (converts), Carbon Monoxide (CO) and Hydrocarbons (HC), into carbon dioxide (CO2) and water (H2O), in an oxidation reaction.

Changes (converts), Oxides of Nitrogen (NOx), into oxygen and nitrogen, in a reduction reaction.

EVAPORATIVE EMISSION CONTROL SYSTEM DESCRIPTION

The EVAP system prevents evaporated fuel from escaping into atmosphere. As the fuel and vapors in the fuel system expand, they are routed to the charcoal (EVAP) canister.

The fuel and vapors are stored in the canister until certain conditions are met. When these conditions are met the purge solenoid is de-energized, allowing the engine to draw air through the charcoal canister. As the air passes through the canister it picks up fuel stored in the canister and carries it into the engine, where it is burned in the combustion process.

POSITIVE CRANKCASE VENTILATION SYSTEM DESCRIPTION

PCV system prevents blowby (emissions produced by the engine combustion chambers which escape into the crankcase) from entering atmosphere. Blowby gases are routed into intake system, where they are burned with air fuel mixture.