Acoustic Control Induction System

Acoustic Control Induction System, or ACIS, is an implementation of a variable-length intake manifold system designed by Toyota.

By energizing the VSV vacuum is passed to the actuator, closing the air control valve.

This effectively lengthens the intake manifold run.

An example of early single-valve ACIS programming would be the 3.0L 3VZ-FE engine.

The ECU actuates the VSV to close the valve when the throttle position is 60% or greater and engine speed is 3,900 RPM or more.