Air Injection: Description and Operation

A.I.R. System Operation:

SYSTEM DESCRIPTION

This system is used to reduce Carbon Monoxide (CO), Hydrocarbon (HC), and Nitrous Oxide (NOx) emissions. It also assist in the heating of the catalytic converter on engine start-up. This allows the conversion of exhaust gases to begin much sooner.

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 contained to one housing. A pipe between the two converters allows air to be injected into the two way converter to increase its efficiency and further control HC and CO.



The A.I.R. system includes:

1. An Air Pump:
A belt driven pump on the front of the engine supplies the air to the system. Intake air passes through a centrifugal filter fan at the front of the pump, where foreign material is separated from the air by centrifugal force.
2. A Control Valve:
Air flows from the pump through an ECM controlled valve, through check valves on either the exhaust ports or the converter.
3. 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.
4. Necessary plumbing.

A.I.R. System Control (PEDES) Valve:

A.I.R. CONTROL VALVE DESCRIPTION

PRESSURE OPERATED ELECTRIC DIVERT / ELECTRIC SWITCHING VALVE (PEDES)

The diverting and switching functions are electronically controlled by the ECM, which grounds the circuit to energize the solenoid. Self-generated pressure from the A.I.R. pump is used to operate the valve, which is independent of manifold vacuum.
When the 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 atmosphere through a divert/relief valve. The divert/relief valve limits system pressure.
Air is diverted to the atmoshere under the following conditions:

1. Rich operation.
2. When the ECM recognizes a problem and flashes the "SERVICE ENGINE SOON" Light.
3. During deceleration
4. During high rpm operation when air pressure is greater than the setting for the internal relief valve.