Air Injection: Description and Operation

Typical A.I.R. System:

SYSTEM DESCRIPTION

This system is used to reduce Carbon Monoxide (CO), Hydrocarbon (HC) and Nitrous Oxide (NO,) emissions. It also heats up the catalytic converter quickly on engine start-up so conversion of exhaust gases will start quickly.

A dual bed converter is used. It consists of a three way catalyst (which controls all three emissions) in series with a two way catalyst (which controls only HC and CO). Both are in one housing. A pipe between the two converters allows air to be injected into the two way converter to increase its efficiency to further control HC and CO.



The A.I.R. system includes:

^ An Air Pump:
A belt driven pump on the front of the engine and supplies the air to the system. Intake air passes through a centrifugal filter fan at the front of the pump, where foreign materials are separated from the air by centrifugal force.
^ A Control Valve:
Air flows from the pump through an ECM controlled valve (called a control valve) through check valves to either the exhaust ports or the converter.
^ Check Valves:
The check valves prevent back flow of exhaust into the pump in the event of an exhaust backfire or pump drive belt failure.
^ Necessary plumbing.

Electronic Air Control Valve:

CONTROL VALVE DESCRIPTION

ELECTRIC DIVERT CONTROL (MANUAL TRANSMISSION)

This system is used on models that do not require air injection into the catalytic converter, and is controlled by an Electronic Control Module (ECM). When engine is operating in ``Open Loop'' mode, the valve is energized and air pump output is directed to the exhaust ports. However, a sudden rise in manifold vacuum will close the valve, momentarily diverting air to the air cleaner. When engine is operating in ``Closed Loop'' mode, the valve is not energized and the vacuum signal is blocked. Air pump pressure closes the valve and air is diverted to the air cleaner.