I have noticed that the B20z has an intake manifold which has practically identical plenum and runner specs to the LS IM. However the B20z IM has a large resonance box that sits on top of the IM and feeds into the plenum. What I'm trying to figure out how its going to affect the flow of the head. Does the volume inside the box "count" towards adding more volume to the plenum?







^ Pic of the 'Z' mani w/ out the resonance box. Notice the hole where the resonance box feeds into the plenum



The site where I pulled these pics from had this to say about it:

The idea is that the "resonator" chamber works like long runners and a larger plenum when the pressure waves travel back up the intake from the ports. Compared to the giraffe manifold (B20b) this gives good top end and good midrange grunt. This probably fills in the low-midrange hole we see on a B20 using an LS manifold (see dyno). There is probably a performance draw back to this system in the upper 6k+ rpm range, otherwise wouldn't see this box on the ITR manifold also?

Gives "good top end and midrange"???
Didn't know you could have your cake and eat it too on a singel stage IM.......

"Low to mid range hole w/ the LS IM"???
This is news to me.......low and midrange is where the LS IM shines.

I'm taking that explanation with a grain a salt because of some of those statements listed above.

As explained in an IM tech article on team-integra.net, I understand the theory that the intake plenum acts like an "ocsillating spring" that compresses and stores the reflected air/sound waves. The energy is then released or "sprung" back down the runner at a pressure that is hopefully greater than the pressure created by the piston sucking in the new air charge on its downward stroke. I'm just confused as to how this resonance box will affect this theoretical block and spring analogy.....and how it will affect head's flow and in turn shift my powerband up or down in relation to using the LS IM which does not use an external resonance chamber.