VARIABLE AIR DUCT (VAD) SYSTEM OPERATION [L5]

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Engine speed less than approx. 5,800 rpm (VAD shutter valve closed)

• Intake manifold vacuum stored in the vacuum chamber is introduced into the VAD shutter valve actuator because of the VAD solenoid valve operation (OFF), causing the VAD shutter valve to close.

• Under this condition, the opening area for air intake is equal to the fresh-air duct opening area. As a result, intake air noise is reduced.

Engine speed approx. 5,800 rpm or more (VAD shutter valve open)

• Barometric pressure is introduced into the VAD shutter valve actuator because of the VAD solenoid valve operation (ON), causing the VAD shutter valve to open.

• Under this condition, the opening area for air intake is the sum of the fresh-air duct opening area and the VAD shutter valve opening area, thus intake air resistance is reduced. As a result, engine output in the high engine speed range is improved.