Thermostatic Air Cleaner: Description and Operation

Heated Inlet Air System:

SYSTEM OPERATION

This system is part of the air cleaner assembly, and its main purpose is to reduce hydrocarbon (HC) emissions and improve cold driveability. It does this by maintaining a certain temperature inside the air cleaner assembly. By maintaining this temperature, the air/fuel mixture can be adjusted much leaner to reduce emissions and help cold running characteristics. This system maintains this predetermined temperature through the use of manifold vacuum, a temperature sensor, and a vacuum diaphragm that operates the heat control door in the air cleaner snorkel.

The heated inlet air system has two circuits of air flow for different ambient conditions. When the ambient temperature is 8°C (15°F) or more above the temperature of air in the warm air duct, the inlet air will come from the outside air inlet. When ambient air temperature is 10°F or more below the temperature of the exhaust stove air, then inlet air will come from the exhaust stove into a flexible tube, into an adapter on the bottom of the snorkel, and into the air cleaner. When the ambient air temperature is between these temperatures there will be air flow through both circuits after the engine has started and the exhaust manifold starts to radiate heat. The colder the ambient air temperature, the greater the flow from the exhaust stove. The warmer the ambient temperature, the greater the air flow through the outside air inlet.