Air Injection: Description and Operation

Air Injection System:

PURPOSE

The air injection system adds a controlled amount of air to the exhaust gases aiding oxidation of hydrocarbons and carbon monoxide in exhaust stream. The system does not interfere with the ability of the EGR system to control nitrous oxide (NOx) emissions.


CONSTRUCTION

The air injection system consists of:

^ A belt-driven air pump

^ An air control valve (either a diverter valve, relief valve or switch/relief valve)

^ Rubber hoses and check valves

The check valves protect the hoses and injection tubes from hot exhaust gases.


OPERATION

Air is injected at either the exhaust manifold (referred to as upstream) or at the catalytic convertor (referred to as downstream). All injected air is routed by the air switch/relief valve.

The [1][2]air switching valve is operated by manifold vacuum. The vacuum supply for the air switch/relief valve is controlled by the air switching solenoid. The solenoid is controlled by the engine controller.

Air is injected upstream at the exhaust manifold for a short time during engine warm-up. Once the engine reaches operating temperature, the air flow is switched downstream. Downstream air flow assists the oxidation process in the catalyst, but does not interfere with EGR operation.