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QUOTE (Rusty @ Dec 16, 2007 - 2:24 AM)

>As far as I know its the factory ST202 radiator
how far down for the tag?
The TVIS system really wasnt all that cool: Youve got a set of narrow intake runners for the low RPMs (means faster moving air, means more air packs into the cylinders), and youve got a set of big runners for the high RPMs (means engine is hungary for air and your want it to flow like crazy), and youve got some flaps to switch between the two.
The ACIS system was a whole other tactic i terms of naturally aspirated power. You know Yamaha built the heads of the later generations of 3SGE and they dont mess around.
Stands for Acoustically Controlled Iduction system, the idea was to keep the runners nice and fat so the engine breathes easy, but to harness the huge sound wave generated by the intake vavles slamming shut at the end of the intake stroke.
At low RPMs, when those valves slam shut they send a sound wave, a pulse of compressed air, back up the intake runners. The manifold was designed so that the pulse could travel up the runner, bounce off a flat surface (that second plenum you see) and return back down the runner and reach the valve just as it opened again. That means each cylinder is getting burst of comressed air, generated by its own valvetrain.
High RPMs, flaps close off that second plenum, and business continues as usual.
this
site is ok, but its just written by some guy, and its a bit inaccurate