THERMACTOR System: Operation: Notes

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

In the Managed Thermactor Air system, air is bypassed to the atmosphere by a Thermactor Air Bypass valve and is directed upstream near the exhaust manifold or downstream to the underbody catalytic converter by the Thermactor Air Control valve. Some models may use a combined Air By-Pass/Air Control valve.

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

In the Extended Idle Air bypass system, a normally closed Idle Tracking Switch opens when the throttle returns to idle, signaling the MCU to de-energize the normally open solenoid valve. Vacuum is then supplied to the normally open bypass valve which dumps thermactor secondary air to the atmosphere.

The Thermactor Air Timer System uses a timer to hold the solenoid valve open for 100-180 seconds thus directing carburetor spark port vacuum to both upper and lower ports of the vacuum control valve when the engine is started. If the engine is cold, only the upper port is open and thermactor air goes to the cylinder heads. If the engine is hot, only the lower port is open and vacuum is admitted to control valve only for duration of timed cycle. When cycle ceases, valve closes and vacuum is vented to atmosphere, while thermactor is directed to catalyst.