Air Injection: Description and Operation

Fig. 4 Secondary air supply system. Models w/pulse air feeder (Typical):

MODELS W/PULSE AIR FEEDER
On this system, Fig. 4, a Pulse Air Feeder (PAF) is used to supply secondary air to the exhaust system between the front and rear catalytic converters. This secondary air combines with exhaust gasses to promote further oxidation in the rear catalytic converter.
A main and sub-reed valve is incorporated in the Pulse Air Feeder. The main reed valve is actuated by a diaphragm which senses pressure pulsations caused by piston movement in the No. 3 cylinder. The sub-reed valve is actuated by exhaust gas vacuum caused by pulsations in the exhaust system between the front and rear catalytic converters.

Fig. 5 Secondary air supply system. Models less pulse air feeder (Typical):

Fig. 6 Secondary air supply system. Models less pulse air feeder w/secondary air valve (Typical):

MODELS LESS PULSE AIR FEEDER
On this system, Figs. 5 and 6, the reed valve(s) supplies air into the exhaust manifold to promote further oxidation of exhaust emissions. Vacuum in the exhaust manifold, caused by pulsations of the exhaust valves, actuates the reed valve(s) and supplies air drawn from the air cleaner to the exhaust manifold and/or rear catalytic converter, depending on application.
On some models, a secondary air control valve is opened by intake manifold pressure when solenoid valve is energized by the ECU. The ECU energizes the solenoid valve based on coolant temperature, intake air flow, engine speed, ignition switch position and idle position.