What VIAS Means:
Variable Intake Air System (VIAS) also Variable Induction Air Control System. Nissan/Infiniti uses the VIAS to reduce the intake suction resistance of the intake air at higher speeds.
When the engine is running at low or medium speed, the VIAS 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.
When engine is running at high speed, the Engine Control Module (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.