Air Injection: Description and Operation

Fig. 81 Secondary air supply system. Exhaust manifold side.:

Fig. 82 Secondary air supply system. Intake manifold side.:

This system, Figs.81 and 82, uses vacuum pulses in the exhaust manifold to draw air from the air cleaner to the exhaust manifold to promote oxidation of hydrocarbons.
The control unit actuates the air suction control solenoid valve which applies manifold vacuum to the air suction cut-off diaphragm valve, opening the secondary air passage. When vacuum, created by exhaust pulses, opens the air suction read valve, fresh air pours into the exhaust manifold.
Air bleed valve B is designed to cut off manifold vacuum flow to the air suction cut-off diaphragm. When air bleed valve B opens, fresh air does not pour into exhaust manifold because air suction cut-off diaphragm valve closes the secondary air passage. The air chamber acts as a silencer to reduce exhaust noises.
When the engine coolant temperature is below set temperature of thermovalve C, Figs. 82 and 83, fresh air pours into auxiliary intake manifold to prevent an overrich mixture. While starting engine, the cranking solenoid valve cuts off the secondary air passage to ease starting of engine.