ACIS (Acoustic Control Induction System)- The Basics

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Quote :

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 engine control unit (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. Toyota ACIS is an On/Off system. The valve (or valves in newer models with multiple valves to create more than 2 lengths) is either fully opened or fully closed. 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 at a TPS (throttle position sensor) input of 60% or greater AND 3,900rpm or greater.


ACIS is NOT a gradual system.

Or simpy put, the ACIS allows the intake manifold to divert the path of intake air into the combustion chamber (located closest to the strut brace). Two air intake paths are provided in the intake manifold to allow the option of the intake volume most favorable for the particular engine speed. Optimum performance is achieved by switching the intake air control valve from either the closed postion(for high tourque at low rpm) or the open position(for maximum horsepower at high rpms).

the ecu signal applies a stop signal to the pressure regulator, by cutting off the vacum, and the return spring opens the butterflys into the open position....'


...It appears that there is an ecu triggered solenoid valve connected to a vacuum operated actuator which is connected to a lickle arm that opens a set of flaps. At approx 5krpm the ecu provides a route to earth for the VSV, it opens and lets the vacuum through, which operates the actuator and flaps the flaps....

Great discussion here

http://www.supramania.com/forums/showthread.php?t=40185

I know its a different system but still works the same.

Just so you know, im adding all this info in this thread then making a complete write up on it

I tell you what, this is really confusing, my head is in pain.

When the ACIS valve/flaps open, It's supposed to make the intake shorter but i cant see how From what i'm seeing, the intake is being made longer due to the intake chamber opening up

I think this is totally different from the ACIS on the Camry's and what not, my head hurts

It's quite a complicated system, something i have never got my head round, need to mount a camera to watch the ACIS lever and diaphragm and watch when it moves. Some say the valves open when you give it full throttle but that doesnt seem right, why would you make the runners shorter at low rpm?

Finally got it sussed. It doesn't change runner length, it changes the Volume of the intake. So really, it's nothing like the ACIS on the 7MGE and other engines.

On the gen 3 3SGE, with the valves shut, the volume is 1.4L. When you hit 5100rpm, the flaps open expanding the volume to 1.9 L.

I.E - At low to mid RPM, you want a smaller intake volume (to a certain extent) for better performance down low. At high RPM, you want a bigger intake volume (to a certain extent)for better top end performance.

I shall make a write up about it

My head no longer hurts