Air Injection: Description and Operation

The air injection system is used to allow fuel that did not burn during the power stroke to continue burning in the exhaust system. This is acomplished by introducing fresh air near the exhaust valve, thus giving the fuel more oxygen to burn with. Air is supplied to the exhaust manifold through the air suction valve.

Fig. 45a Air Injection System:

When the air suction solenoid valve is activated, manifold vacuum raises the diaphragm of the air suction valve and fresh air from the air cleaner is induced to the exhaust manifold. The fresh air is induced to the exhaust stream by the pulsations of the exhaust. At low engine speeds, the exhaust stream is a series of high and low pressure pulses. The reed valve in the air suction valve blocks the high pressure pulses and lets fresh air in to fill the low pressure pulses.