Emission Control Systems: Description and Operation

The emission control system consists of devices to control tailpipe emissions as well as hydrocarbons produced by evaporating fuel and combustion gases that escape through the crankcase into the atmosphere.
The primary emission control system is the fuel injection system. The Bosch Fuel injection system offers more precise fuel control over a wider range of conditions than can be achieved with a carburetor. The use of an exhaust gas oxygen sensor, catalytic converter, 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.) allowing the catalytic converter to operate at peak efficiency.
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.
Emissions produced by the engine combustion chambers which escape into the crankcase are prevented from entering the atmosphere by recirculating the gases back into the intake system to be burnt along with the incoming air/fuel mixture.
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.