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.

Pressure Operated Electric Divert/Electric Switching (PEDES) valve:

CONTROL VALVE DESCRIPTION

PRESSURE OPERATED ELECTRIC DIVERT / ELECTRIC SWITCHING VALVE (PEDES)

This valve, is ECM operated similarly to the ED/ES type, but uses air pump pressure rather than intake manifold vacuum to operate control valves. Air pump pressure builds up against a control valve which is operated by the ECM through 2 solenoids.
When engine is cold (``Open Loop''), the port solenoid is energized and air pump pressure opens the passage to the exhaust ports. During normal operation (``Closed Loop''), the port solenoid is de-energized, the converter solenoid is energized, and air pump pressure opens the passage to the catalytic converter. When the ECM determines that air divert is necessary, both solenoids are de-energized and air pump output is diverted to the air cleaner through a divert/relief valve. The divert/relief valve limits system pressure.
Air is diverted to the atmosphere under the following conditions:
^Rich operation.
^When the ECM recognizes a problem and sets the "Service Engine Soon Light.
^During deceleration
^During high rpm operation when air pressure is greater than the setting for the internal relief valve.