So ive been looking at pictures of 2nd and 3rd gen 3sge's and for the life of me I can't see how ACIS would work? I understand a butterfly valve opens up and closes passages but I don't see how the Air Flow goes through the upper portion since it's sealed off. What exactly am I missing here?

great info can be found in here, ACIS & BEAMS discussion thread

theres not really a good explanation on that page with a good picture like that though so i'll explain it now.

short path = good high rpm

long & slightly restricted path = good low rpm


see in that picture how those throttles are sitting upright it? thats long path, some of the air flows over the top & the path underneath is slightly reduced in diameter by the throttles being in that position.

when its in short path that top chamber is completely sealed off by those throttles, and theres no restriction to the path underneath.

the idea is having 2 different sized manifolds in 1 with 2 rounds of high volumetric efficiency in 2 different rev ranges.

the tps is used also so that the restriction is lifted during low throttle operation to reduce extra pumping loss, but thats not so important to know.