Emission Control Systems: Description and Operation

The emissions control system consists of devices to control tailpipe emissions as well as hydrocarbons produced by evaporating fuel.
The primary emission control system is the fuel injection system. The Bosch CIS-E III injection system (also known as KE3-Jetronic) offers more precise fuel control over a wider range of conditions than can be achieved with a carburetor or the earlier CIS injection systems. The use of an exhaust gas oxygen sensor 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 aid in cold running, a thermostatic air cleaner is used to preheat incoming air to the engine. The air, (warmed by the exhaust manifold), allows for improved vaporization of the fuel, thus improving cold weather driveability and reducing hydrocarbon emissions.
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.
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 rawing in and burning the stored fuel vapors.