THERMACTOR System: Operation: Notes

The air pump supplies air under pressure to the exhaust port near exhaust valve by either an external air manifold, or through an internal drilled passage in cylinder head or exhaust manifold. This pressurized air, combined with hot exhaust gases, creates a secondary combustion stage which produces carbon monoxide and water.

In the MTA system, air can be by-passed to the atmosphere by a thermactor air by-pass valve, and/or directed near exhaust manifold, or underbody catalytic converter. Some models may use a combined air by-pass/air control valve.

In the Thermactor II system, natural pulses present in the exhaust system are used to pull air into exhaust manifold through a Pulse Air Valve (PAV). The pulse air valve is connected to exhaust manifold by a tube, and to air cleaner by a hose.

In the Extended Idle Air By-Pass system, a normally closed Idle Tracking Switch (ITS) opens when throttle returns to idle. This signals the EEC module to de-activate the normally closed solenoid valve. Vacuum is removed from the normally closed by-pass valve, causing thermactor secondary air to be released into atmosphere.