Contour Enthusiasts Group Archives Forums Branches South Central Demon, I got my new intake manifold for my Maxima. I've got a ?

I received my new JDM-spec manifold today and I still can't quite understand the idea behind why this intake manifold breaths so well in the upper rpms. Here's a pic:

http://home.earthlink.net/~thunderlt1/_uimages/MyPictures0001.jpg

Most dual stage intake manifolds (like the Contour SVT, 00+ Maxima) use two set of runners, long and short, to maximize lowend torque and upper rpm HP. This manifold look EXACTLY like the US-spec manifold (only one set of long runners) EXCEPT the difference is that there is a chamber that sits on top of the manifold which is seperated by a set of butterfly valves. At a determined rpm (~5200), the butterflys open up to the upper chamber. This chamber is sealed with a lid (pictured above the manifold). All I can think is that this chamber somehow "ramps up" the intake charge and increases the velocity thru pressure and resonance. What's your expert take?

Dynos have shown the manifold to make power straight to the 6550rpm fuel cut with gains exceeding 25fwhp after 5300rpms and ET drops of .3-.4 and gains of 3-4mph.

Dave