View Full Version : Another ACIS Question

11-03-2009, 05:01 AM
I've done all the searching and have read most thread on the internet but cant grasp how this works.

I know how it works as in operation, just not in theory.

With the keys out the ignition, the flaps stay open.

Start the car and the flaps close.

When you hit 5100rpm, the flaps open.

So when the flaps open, the top intake chamber opens up.

From what i understand, you want long intake runners at low - mid range RPM and short intake runners at high RPM.

What i dont understand is if the flap is closed at low rpm, doesnt that mean its using a short runner?

And when you hit 5100rpm, the flaps open creating a long intake runner.

Shouldn't it be the other way round?

Just cant understand it.

11-03-2009, 06:48 AM
ACIS has nothing to do with runner length it's about plenum volume.

11-04-2009, 04:30 AM
the volume changes from (well on 3gen) 1.4L to 1.9L, anyone have the actual figures?

11-04-2009, 10:42 AM
Aahh i get it, i kept thinking it changes runner length :lolhittin

So, when under 5100rpm, the flaps are shut thus making the volume 1.4L. When the flaps open, the volume expands to 1.9L.

It's quite simple now i think about it, been trying to figure it out for ages.

Also if you dont mind me asking, i know on the 7MGE (?) i think it is, when your below 4800rpm and you give it over 60% throttle, the valves open up.

I've been told by a guy with a 3SGE MR2 that when you floor it, the valves should automatically open, doesn't matter what RPM your at. Is this true?

I know mine only open when you hit 5100rpm but he is sure that it's vacuum dependant and not rev dependent, in other words, it will open when ever you give it gas, no matter what rpm.

Im sure it's ECU triggured with an actuator and diagphragm but he says im wrong :s

Sorry for the long question, Thanks guys :bowdown: :bowdown: :bowdown: