Air Injection: Description and Operation

Fig. 33 Air Suction System:

Fig. 34 Air Suction System Schematic:

The air suction (AS) system is used to direct air into the engine exhaust ports to extend the combustion of unburned hydrocarbons (HC) and carbon monoxide (CO) in the exhaust system. Air is also used as the oxygen source for the catalytic converter. Air flow is controlled by a valve assembly that includes a vacuum operated shut-off valve and reed valve. During normal operation, the shut-off valve is held open by manifold vacuum. Vacuum created by exhaust pulses opens the reed valve permitting air to be drawn into the exhaust stream. The AS system is regulated by the electronic control unit (ECU) which monitors the engine temperature, throttle position, air flow, vehicle speed, and engine speed to determine when to apply vacuum to the air suction valve.