THERMACTOR System: Operation: Notes

Inlet air to air pump is drawn through a centrifugal air filter fan. Air pump then supplies air under pressure to exhaust port near exhaust valve, by either an external air manifold, or through an internal drilled passage in cylinder head or exhaust manifold. Oxygen in fresh air, plus heating of exhaust gasses, cause further burning which converts gasses into carbon dioxide and water.

In Managed Thermactor Air System, air can be by-passed to atmosphere by a Thermactor Air By-Pass Valve and/or directed upstream near exhaust manifold or downstream to underbody catalytic converter by Thermactor Air Control Valve. Some models may use a Combined Air By-Pass/Air Control Valve.

In Thermactor II System, natural pulses present in exhaust system are used to pull air into exhaust manifold through a Pulse Air Valve. Pulse air valve is connected to exhaust manifold with a tube and to air cleaner with a hose.

In Extended Idle Air By-Pass System, a normally closed Idle Tracking Switch opens when throttle returns to idle, signaling EEC Module to de-energize normally closed solenoid valve. Vacuum is removed from normally closed by-pass valve causing thermactor secondary air to be dumped into atmosphere.

When engine is started, Thermactor Air Timer System uses a timer to hold solenoid valve open for 100-180 seconds thus directing carburetor spark port vacuum to both upper and lower ports of Vacuum Control Valve (VCV). If engine is cold, only upper port is open and thermactor air goes to cylinder heads. If engine is hot, only lower port is open and vacuum is admitted to control valve only for duration of timed cycle. When cycle ceases, solenoid valve closes, vacuum source is blocked, VCV is vented to atmosphere, and thermactor air is sent to catalyst.