Air Injection: Description and Operation

AIR System (Turbo):

SYSTEM OPERATION

The system is designed to reduce hydrocarbon (HC) and carbon monoxide (CO) emissions by supplying filtered air into the exhaust ports. When this air meets the hot exhaust gases exiting the combustion chambers, combustion continues, further oxidizing the HC and CO in the exhaust. These pollutants are then converted into carbon dioxide and water vapor. After cold start-up, and during periods of engine warm-up the additional heat energy released helps to bring the catalyst up to operating temperature more quickly.

The AIR system consists primarily of an electric air pump, a vacuum switching valve, an air switching valve, a check valve, and an air manifold. The air pump supplies filtered air through the air switching valve and check valve, into the air manifold where it is distributed to the individual exhaust ports.

Electric AIR Pump:

AIR PUMP

The AIR pump used in this application is unique, and not found on any other Isuzu models for the 1989 model year. It is an integral electric motor driven positive displacement air pump, which operates on 12 volts DC.

Air Switching Valve:

AIR SWITCHING VALVE

The purpose of the air switching valve is to direct the air from the air pump to the exhaust system or to divert it, as needed. The valve is vacuum operated. When manifold vacuum is present at the control port, the valve closes the port to the exhaust check valve and diverts pump air to the air cleaner. As manifold vacuum drops, indicating off idle condition with a load, the valve opens the passage to the exhaust check valve and air is pumped into the exhaust manifold.

AIR Manifold:

AIR INJECTOR MANIFOLD

The air injector manifold distributes the pump air to the individual exhaust ports in the cylinder head.

Check Valve:

CHECK VALVE

The check valve is a one-way diaphragm valve which prevents exhaust gas from escaping into the AIR system when the system is not operating, or in the event of a pump or system failure.

Vacuum Switching Valve:

VACUUM SWITCHING VALVE

The vacuum switching valve is a normally closed, electrically operated vacuum valve. When energized by the ECM, it applies control vacuum to the AIR switching valve, allowing the AIR system to operate. When de-energized, vacuum is blocked and the AIR switching valve diaphragm is vented to the atmosphere, turning "off" the AIR system.