Celica & Matrix (With 2ZZ-GE Engine Only)
Acoustic Control Induction System (ACIS) is a variable induction system that improves engine performance and reduces engine noise by dividing the air intake duct into 2 stages. When engine is operating in low-to-mid speed range, ACIS causes variable intake valve to close one side of the intake air duct. See Fig 1. When engine is operating in the high-speed range, ACIS causes variable intake valve to open, allowing both sides of the intake air duct to supply intake air. Variable intake valve operation is controlled by a vacuum controlled actuator. See Fig 1. Engine Control Module (ECM) controls the ACIS Vacuum Switching Valve (VSV) which controls vacuum supply from vacuum tank to the actuator. See Fig 1. ECM uses engine RPM input signal and throttle position sensor input signal for determining ACIS operation. Engine RPM input signal is provided by camshaft and crankshaft position sensors.