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

It looks like the manifold creates a low pressure chamber directly above the head inlet ports that allows the engine to better pull in the intake air charge.

Instead of pulling it through the entire intake tubes at high rpm (slows velocity), it allows it to pull in air from a low pressure zone very close to the head ports. This way it raises high rpm engine efficiency and therefore it's power & the powerband.

I've seen atleast one Duratec engine (racing of course) that has the LIM opened up and joins the 2 ports (primary & secondary) about where the butterflies used to be. Then it also opens the head ports by joining them together before they split back up at the valves.

This creates a small expansion chamber right at the fuel injectors which accelerates the intake charge and raises high rpm power. Plus as a bonus both valves distribute the fuel & air charge instead of just the primary port.

This is definitely in my bag of tricks if and when I ever do a 3L hybrid...

Thanks. That's what I figured (mostly). I wonder why more companies don't use setups like this? It's actually a very simple idea that goes a long way in terms of performance. Now I'll just have to install it, but that shouldn't be too hard. It will just take a good 5 hours or so to get the manifolds swapped, hook up the Harlan RPM switch, vacumm system, and relay. I'll need to tune on the dyno to find the best RPM switch over too. I'm figuring I'll set it at 5200rpms (HP peak at 5300) to compensate for the valves opening and chamber becoming operational.

I can't wait. My Max will have some serious "legs" on the topend.

Dave