Thermostatic Air Cleaner: Description and Operation

Fig.2 - Induction Air Preheating:

This system, Fig. 2, takes hot air from near the exhaust and mixes it with cool air to provide even induction air temperatures in the lower engine speed ranges.

Fig.3 - Temperature & Load Controlled Induction Air Preheating:

Some models use a system in which air temperature is controlled by temperature conditions as well as engine load, Fig. 3. When the throttle is closed or slightly open with the engine running, the high vacuum created pulls in the diaphragm, opening the control flap and the warm air supply duct. As the throttle is opened wider, the drop in vacuum closes the control flap, allowing less warm air into the induction system. At full throttle, the engine receives only cold air.

The temperature-sensitive control is operated by a bi-metal spring-actuated temperature regulator. As long as air temperature remains below a specified level, the regulator remains closed, allowing warm air to flow to the intake stack. When air temperature exceeds a predetermined level, a valve opens in the temperature regulator and the incoming outside air reduces the vacuum. At this time the control flap in the intake stack closes the warm air supply duct regardless of throttle position.