Air Injection System: Description

Different systems are used on Ford Motor Co. models although the principle operation is identical. The system is used to inject fresh air into the exhaust gases to promote further oxidation of both hydrocarbons (HC) and carbon monoxide (CO), thereby reducing concentration and converting some into harmless carbon dioxide and water.

Managed air thermactor system is utilized in several electronic and non-electronic control systems to divert fresh air upstream to exhaust manifold or downstream to rear section check valve and dual bed catalyst. This system will also dump fresh air into atmosphere during some operating modes. An air control valve is used to direct air either upstream or downstream. An air by-pass valve is used to dump air into atmosphere. These valves may be separate or combined in one valve.

A dual air pump system is used on V8 heavy duty trucks. Two air pumps and 2 air by-pass valves direct air simultaneously to cylinder head check valve and to left and right exhaust manifold check valves. The system will dump air to air cleaner during decel modes and at high speed high back pressure modes.

Pulse air system or thermactor II system does not use an air pump. This system uses natural pulses, present in exhaust system, to pull air into exhaust manifold and/or catalyst through pulse air valves. Pulse air valves are connected to exhaust manifold and/or catalyst with a long tube and to air cleaner or silencer with hose.