Acoustic Control Induction System

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The ACIS/TVIS Sytem

Acoustic Control Induction System, or ACIS, is an implementation of a Variable Length Intake Manifold system designed by Toyota.

Simply put, the ACIS system uses a single intake air control valve located in the intake to vary the length of the intake tract in order to optimize power and torque, as well as provide better fuel efficiency and reduce intake "roar".^[1].

The ECU controls the position of the intake air control valve based on input signals from throttle angle and engine RPM. The vacuum switching valve (VSV) which controls the vacuum supply to the actuator is normally closed and passes vacuum to the actuator when it is energized by the ECU. By energizing the VSV vacuum is passed to the actuator, closing the air control valve. This effectively lengthens the intake manifold run. By de-energizing the VSV, vacuum to the actuator is blocked and trapped vacuum is bled off of the actuator diaphragm. Without vacuum, the air control valve opens, effectively shortening intake runner length^[1]. This logic is the same as that used on the T-VIS system, the primary difference being that T-VIS actuates at a set RPM value whereas ACIS attempts to maintain a constant powerband by opening progressively.