Brat F4-1781cc 1.8L (1982)
Pulsed Secondary Air Injection: Description and Operation
Fig.2 - Air Injection System
This system, Fig. 2, promotes oxidation of hydrocarbons and carbon monoxide under cold operating conditions. It consists of an air suction valve,
cutoff valve, air suction pipe, air introduction hose, air filter, thermosensor, solenoid valve, check valve, and electronic control module.
Exhaust gas pulses are transmitted to air suction valve through air suction pipe. When a negative pressure is present, ambient air flows from air
cleaner to exhaust passage. When positive pressure is present, air switching valve is inoperative.
This system is controlled by both a thermosensor which senses coolant temperature, and time governed by the electronic control module. When
coolant temperature is below a specific value, ECM opens intake manifold vacuum passage of solenoid valve for 123 seconds, which causes
diaphragm vacuum actuator to open cutoff valve and operate air switching valve. After 123 seconds, the ECM closes vacuum passage of solenoid
valve and opens atmospheric pressure passage. The vacuum in vacuum chamber of cutoff valve then flows out through solenoid valve, which
closes cut- off valve and deactivates air switching valve.
Two vacuum switches and a thermoswitch are incorporated into the emission control system. When coolant temperature is below 140"F, (60"C)
and manifold vacuum is less than 7.9 inch Hg, (200mm Hg) for vehicles equipped with manual transmission and 4 inch Hg, (120mm Hg) for
vehicles equipped with automatic transmissions. The ECU opens the solenoid valve circuit by receiving thermoswitch and vacuum switch signals.
When manifold vacuum is less than 3.3 inch Hg, (86mm Hg) the ECU issues a signal to the solenoid valves that the amount of air metered is
constant.
