OK, I'm confused.

I have an 06 G35 6MT Coupe.

After reading about intake plenum spacers, I decided to get a 5/16". Then I read about the MREV and it said it was specifically designed for the Revup engine. I asked a rep at Motordyne and he said I have that engine. The description says it will add 15HP and 18TQ...Wow!

In our conversation, he described how it works and that the MREV lower plenum is a modified lower plenum for an automatic. This, combined with the spacer gives the desired results. He also said that just adding the spacer to my intake will do nothing because my stock lower plenum already has the short intake ports and thus creates more HP than the plenum meant for the automatic G35. The auto plenum creates more torque because it has longer ports but less air volume due to less area inside the plenum chamber, thus less HP. Follow me?

Now I'm confused...

In my head, putting a lower plenum from an automatic on my 6MT means that now I have the resulting 280HP/270TQ auto engine. 18 LESS HP but 10 MORE TQ. So then adding the spacer for increased volume corrects that and I'm back where I started (hopefully) with HP and I get more TQ.

Does this sound right? It does not seem like a wise decision to me but then maybe I'm wrong about this. I have not installed the system yet so I don't have the "seat of the pants" feel yet.

Anyone have any ideas about this?

Modified by The_Scooch at 3:32 PM 8/5/2006
Modified by The_Scooch at 3:35 PM 8/5/2006

That doesn't right to me. I would want to see some dyno numbers first to compare with.

Is there anything wrong with the Skunk2 5/8" Plenum spacer? I've seen it for just over $200. Does its extra thickness cause a drop in pressure in the plenum?

From what I've read so far, the various plenum spacers simply open up the intake plenum a small amount to allow for more even flow of air to all 6 cyclinders. I assume this small amount doesn't effect air velocity or pressure much and simply makes a larger volume of air make it all the way to the front pair of cylinders?

So the smallest spacer will have the smallest pressure drop, but add volume. The larger spacer will have a slightly larger pressure drop and may add more volume.

At some point if you kept going up to a larger spacer, you would eventually start loosing power because there wouldn't be much pressure in the plenum?

Does this work on all G35 6MT Coupes? Do you gain HP with the stock air box, throttle body and intake manifold?

Does anybody make a full aftermarket intake plenum that would produce the same or better results?

I found some more info and I have the answer I was looking for:

First, the MREV and spacer do work and here’s how:

The revup engine (6MT) differs from the 5AT in a few ways but one significant difference is the shape and port length of the lower plenum. More torque is needed for an automatic transmission and so to give the 5AT engine a different power profile, Nissan engineers created a lower plenum with long ports. This takes up extra space in the chamber, thus lowering the volume of air while increasing port velocity. For the 6MT, the opposite was done. The ports were made shorter and the plenum slightly dished to allow more air volume and less restricted flow.

The result is in the numbers; the 5AT has more torque and the 6MT has more HP.

Installing the spacer alone on a 5AT corrects the volume problem, thus increasing HP. Nothing more needs to be done to the 5AT. Installing a spacer on a 6MT will accomplish next to nothing and could hurt top end power. The solution is to install the MREV kit. The kit consists of a 5AT lower plenum that Motordyne says they have modified for improved flow, and a 5/16 spacer. The ½ spacer allows a little more volume and the pressure drop hurts the midrange power. The result is NOT more top end power, but instead, more torque and more HP in the mid to upper mid range. The dyno shows approximately a 15 HP increase and 18 ftlb torque increase across the powerband. HP peaks slightly higher than stock at around 6200 RPM, levels off and then drops to about 2 HP less than stock at redline. This test was done on a forum member’s 350Z.

I don’t drive around at the redline so I am happy to sacrifice the 2 HP. The usable HP and torque increases are right where they will be the most fun.

So I figure with an exhaust and a Z-tube, I should get over the 300 HP mark ( a claim I want) while still improving the power curve and driveability.

See my post to RydWhite.