Air Injection Reaction: Also known as A.I.R. or ‘Air Injection Reactor’. Became common in 1974, but not all manufacturers utilized an A.I.R. system.
The A.I.R. system is probably the number one ugly thing that was done to engines of the smog-era. The core of the system is really not that ugly and is usually tucked out of view. It’s a belt-driven piece called an air pump (also know as smog pump). It’s designed to push fresh air into the exhaust manifolds. Sometimes the catalytic converter gets a supply line for air as well.
The ugly parts of the system are the yards of rubber air hose & vacuum line, 2 or 3 one-way check valves, diverter valve, diverter muffler, manifold tubing, and on some cars an electronic control box.
The overall process effectively adds oxygen to unburnt and partially burnt fuel. It completes the burning process where the car is the hottest— exhaust manifold and catalytic converter. This helps lower the carbon monoxide and hydrocarbons in the exhaust.
These systems help a great deal with controlling pollution, but are not very friendly to the necessity of having a clean engine compartment.