System Description

VIAS SYSTEM DESCRIPTION

Sensor

Input Signal to ECM

ECM function

Actuator

Mass air flow sensor

Amount of intake air

VIAS control

VIAS control solenoid valve

Throttle position sensor

Throttle position

Accelerator pedal position sensor

Closed throttle position

Battery

Battery voltage⁽¹⁾

Crankshaft position sensor (POS)
Camshaft position sensor (PHASE)

Engine speed⁽¹⁾

Engine coolant temperature sensor

Engine coolant temperature

⁽¹⁾	ECM determines the start signal status by the signals of engine speed and battery voltage.

Fig 1: Identifying VIAS System

Courtesy of NISSAN MOTOR CO., U.S.A.

When the engine is running at low or medium speed, the power valve is fully closed. Under this condition, the effective suction port length is equivalent to the total length of the intake manifold collector's suction port including the intake valve. This long suction port provides increased air intake which results in improved suction efficiency and higher torque generation.

The surge tank and one-way valve are provided. When engine is running at high speed, the ECM sends the signal to the VIAS control solenoid valve. This signal introduces the intake manifold vacuum into the power valve actuator and therefore opens the power valve to two suction passages together in the collector. Under this condition, the effective port length is equivalent to the length of the suction port provided independently for each cylinder. This shortened port length results in enhanced engine output with reduced suction resistance under high speeds.