Heated Inlet Air System Operation
PURPOSEThe heated air inlet system controls and maintains the temperature of the air entering the throttle body. By maintaining the inlet air temperature, the air- fuel mixture can be calibrated much leaner to reduce hydrocarbon emissions. It also improves engine warm-up characteristics and minimizes icing.
CONSTRUCTION
The system consists of:
^ A diaphragm that operates the blend door in the air cleaner. This door opens to either heated air or ambient air.
^ A heated air temperature sensor
^ An air duct hose connected to a heat stove on the exhaust manifold.
OPERATION
The air cleaner blend door opens to either:
^ Ambient (outside) air
^ Preheated air from the heat stove
^ Or a controlled position between outside air and preheated air
Heated Air Inlet System:
The heated air temperature sensor in the air cleaner senses inlet air temperature. The sensor also controls the flow of vacuum to the air cleaner blend door vacuum diaphragm. It will then control the air temperature going into the intake manifold. The amount of air allowed to enter from ambient (outside) and heat stove inlets is determined by position of blend door in air cleaner snorkel.
The blend door vacuum diaphragm is opposed by a spring. Throttle body inlet air temperature adjustment will occur only when intake manifold vacuum is above operating vacuum of vacuum diaphragm.
The system is designed to maintain the throttle body inlet air at a calibrated temperature. Air will flow through outside (ambient) opening when ambient air temperature is 5.6°C (10°F) or more above system calibration temperature.
When ambient air temperature is 4.4°C (8°F) or more below system calibration temperature, air flow will be through heat stove inlet of the air cleaner.
At intermediate temperatures, the air entering the throttle body is a blend of ambient air and heat stove air. The colder the ambient air, the greater the flow of air through the heat stove. The warmer the ambient air, the greater the flow through the snorkel.