Air Injection: Description and Operation

Fig. 1 - Typical Installation Of Air Pump System With Diverter Valve Also Known As Air Bypass Valve:

NOTE: A properly operating AIR system effectively reduces emissions however if any component related to the system malfunctions emissions may be increased.

CAUTION: Due to design differences, carburetors and distributors for engines equipped with air pump systems should not be interchanged with carburetors or distributors designed for engines without air pump systems.

Fig. 2 - Air Pump With Integral Centrifugal Air Filter & Pressure Relief Valve:

Fig. 3 - Air Pump With Centrifugal Air Filter Without Pressure Relief Valve:

PURPOSE
The Air Injection Reaction (AIR) system reduces the emission of Hydrocarbons (HC), and Carbon Monoxide (CO).

OPERATION
The air injection system, Figures 2 and 3, supplies the oxygen needed to ignite and burn any unused fuel in the exhaust system by injecting fresh air into the exhaust system--near the exhaust valves--via the air manifolds, hoses and injection tubes

Fig. 4 - Typical Diverter Or Air Bypass Valve:

Fig. 5 - Typical Diverter Or Air Bypass Valve With Integral Pressure Relief Valve:

Diverter or Air By-pass Valve Operation
The diverter--or air by-pass valve, Figs. 4 and 5--prevents backfiring--when triggered by a sharp increase in manifold vacuum--by shutting off the injected air to the exhaust port areas during this richer period.

Engine Over-run
On engine over-run the total air supply is dumped to atmosphere--through the muffler or the diverter or air by-pass valve.

High Engine Speed Operation
- When the pressure relief valve is part of the air pump--Fig 2. excess air is dumped to atmosphere through the pressure relief valve.
- When the pressure relief valve is part of the diverter or air by-pass valve--Fig 5, excess air is dumped to atmosphere through the diverter or air by-pass valve.

Fig. 6 - Deceleration Valve:

Deceleration Valve Operation
The deceleration valve--Fig 6--used on some 1981-82 vehicles--prevents backfiring in the exhaust system during deceleration by supplying the additional oxygen needed to burn the fuel supplied.
- When the throttle valve closes on deceleration manifold vacuum increases abruptly, the pressure differential on the diaphragm overcomes spring tension, opening the valve and bleeding air into the intake manifold.
- Air trapped in the chamber above the vacuum diaphragm will be bled at a calibrated rate through the delay valve portion of the integral check and delay valve, reducing vacuum on the diaphragm.
- When vacuum on the diaphragm and spring tension become equal, the valve closes and cuts off air supply to the intake manifold.
- The check valve portion of the check and delay valve provides a rapid balancing of chamber pressure when there is a sudden decrease in vacuum during acceleration.

COMPONENTS--Fig 1
- Air injection pump
- Air injection tubes--one for each cylinder
- Diverter or air by-pass valve
- Check valves (one for In-Line engines, two for V8s)
- Air manifolds, tubes and hoses necessary to connect the various components.

NOTE: Not all systems contain all components listed above.

NOTE: Carburetors, distributors and control valves are designed for specific engine applications and should not be interchanged with other units.