Components

Components

[Graphic title: “Air Injection System Components

[Insert air injection system graphic labeled with term numbers below]

Air injection systems differ between automakers, but most consist of four primary components as seen in the graphic. The main components of an engine air system are:

  1. Secondary Air Pump (or ‘SmogPump’)
  1. Diversion Valve (or ‘BypassValve’)
  2. CheckValve
  1. Air Manifold (or‘Tubes’)

These components work together to inject air into engine exhaust, and all air system components must be present and functioning when required. Vehicles using this basic system date back to the mid 1960s, but not all vehicles from that era were required to have secondary air

systems at all. Let’s see what each air system component does.

  • Secondary Air Pump (or ‘SmogPump’)

The secondary air pump, or ‘smog pump,’ is a belt-driven or electric air pump designed to push air to the other components in the system. A failing smog pump is a common cause of an HC failure during emissions

testing. The smog pump is routed directly to the diversion valve, or

‘bypass valve.’

·

The diversion valve or ‘bypass valve’ uses engine manifold vacuum or an electric solenoid to regulate the flow of air to the exhaust. The diversion valve helps to adjust the air injection system to different engine and driving conditions, thus reducing the efficiency of the system and

minimizing performance loss. After reaching the diversion valve, air flows through hoses to one or more check valves.

  • CheckValve

Vehicles equipped with air injection systems use check valves to combat backpressure from the exhaust system. This is to ensure a one-way flow of air into the air manifold and avoid exhaust gasses flowing back into

the diversion valve or smog pump. Once the air passes through the check valve, it moves into the air manifold.

  • Air Manifold (or‘Tubes’)

The air manifold, sometimes called the ‘air tube,’ is designed to equally distribute air from the smog pump into each of the engine’s exhaust

ports. Some air manifolds funnel air directly into ‘mounting points’ in either the cylinder head exhaust ports or into the exhaust manifold itself.