Emission Control Systems: Description and Operation

To reduce exhaust emissions, these vehicles use a deceleration control system, evaporative emission control system, exhaust gas recirculation system, positive crankcase ventilation system, three way catalytic converter, and electronic gasoline injection.

EVAPORATIVE EMISSION CONTROL SYSTEM (EVAP)
The evaporative emission control system stores fuel vapor in a charcoal canister when the engine is not running. Fuel vapor is stored until drawn into the dynamic chamber and burned when the engine is running.

EXHAUST GAS RECIRCULATION SYSTEM (EGR)
The exhaust gas recirculation system introduces exhaust gas into the intake manifold to reduce NOx emissions. It operates depending on engine load, engine speed, and coolant temperature.

POSITIVE CRANKCASE VENTILATION SYSTEM (PCV)
The PCV valve is operated by intake manifold vacuum. When the engine is running at idle, the PCV valve is opened slightly and a small amount of blow-by gas is drawn into the engine. At higher engine speeds, the PCV valve is further opened and a larger amount of blow-by gas is drawn into the engine.

THREE WAY CATALYTIC CONVERTER (TWC)
The catalytic converter is used to convert exhaust emissions CO, HC, and NOx into carbon dioxide, water vapor, and nitrogen gas. Platinum, palladium, and rhodium are catalysts used to stimulate reactions that accomplish these conversions.