Sundance L4-153 2.5L SOHC Turbo (1990)
Heated Inlet Air System: 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 prevent throttle body icing. 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 starting 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 assembly.
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 radiating from the exhaust manifold, the inlet air will come from the outside air inlet. When ambient air temperature is 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 temperatures, the greater the flow from the exhaust stove. The warmer
the ambient temperatures, the greater the air flow through the outside air inlet.
