Dual Air Pumps

Dual Air Pump Injection System:

Air Injection System:

SYSTEM OPERATION

The air injection system is composed of two belt-driven air pumps, two air control valves (diverter valves, or switch/relief valves), rubber hoses, coolant temperature sensor, check valves to protect the hoses, and injection tubes. This system adds a controlled amount of air to the exhaust gases aiding the reduction of hydrocarbons and carbon monoxide in the exhaust stream.

Air passes through the plastic centrifugal filter fans at the front of the air pumps, and foreign materials are filtered out of the air by centrifugal force. Air is then injected at the exhaust ports for a short time during engine warm-up. The air flow is then switched to a point downstream where it will assist the oxidation process in the catalyst but not interfere with exhaust gas recirculation. The switching is controlled by an electronically controlled vacuum switch.


CHECK VALVE

The check valves are located in the injection tube assemblies. One upstream in line with the exhaust manifolds, and the other one downstream at the catalyst injection point.

The purpose of the check valve is to protect the air injection system in the event that the air pump belt fails, exhaust system pressure raises to an abnormally high level, or an air hose ruptures. This valve has a one way diaphragm which prevents hot exhaust gases from getting to the rubber hoses or the air pump.

Coolant Temperature Sensor (Typical):

COOLANT TEMPERATURE SENSOR

This sensor is a part of the Air Injection and EGR electrical system. It tells the SMEC when to activate either of these systems.

Diverter Valve:

DIVERTER VALVE (SOME MODELS)

The diverter valve is located upstream of the switch/relief valve. It's purpose is to prevent backfire during deceleration. The diverter valve senses changes in manifold vacuum. When decelerating, vacuum increases rapidly. This increase causes the valve to open thus allowing air from the air pump to vent through the silencer and out to the atmosphere. When accelerating, vacuum drops rapidly. This decrease in vacuum causes the valve to shut allowing air to flow either upstream or downstream.
A pressure relief valve is also incorporated into the diverter valve. It's purpose is to allow excessive air pump output to be vented to the atmosphere under high system pressure conditions (approximately 9 psi), specifically high engine speeds.