Emission Control Systems: Description and Operation

PURPOSE

The emission control system is used to reduce harmful gases in accordance with federal and state regulations. The gases targeted for reduction are:
CO - Carbon Monoxide - the product of incomplete burning of gasoline.
HC - Hydrocarbons - unburned gasoline vapors
NOx - Oxides of Nitrogen - a product of high combustion temperatures and pressures

OPERATION

The emission control system has four sub systems:

^ CRANKCASE EMISSION CONTROL SYSTEM.
Prevents blow-by gases, which are high in CO and HC, from escaping into the atmosphere. The blow-by gases in the crankcase are routed, through various components, back into the intake manifold for combustion.

^ COMPUTERIZED ENGINE CONTROL SYSTEM.
Consists of an Engine Control Module (ECM) and various sensors and output devices. This system controls engine operation (i.e. Air/Fuel mixture, idle speed and ignition timing) to reduce pollutants while maintaining optimum driveability conditions and reducing fuel consumption.

^ EVAPORATIVE EMISSION CONTROL SYSTEM.
Prevents the escape of fuel vapors from the Fuel Tank and fuel system into the atmosphere. It consists of various components, which collect and lead the fuel vapors to the intake manifold for combustion.

^ EXHAUST EMISSION CONTROL SYSTEM.
Consists of a three-way catalytic converter, which reduces all three exhaust gases.