MEVI Swap

For those of you who are new to the site. A MEVI is called a Middle Eastern Variable Intake. It is the Intake Manifold that comes on all JDM Cefiro's. The A32 Maxima's don't have these intake manifolds and suffer the loss of high end power because of it.

The MEVI however is not all “great”. It has its cons. The MEVI, for what it makes up for up high in the rpm range, it lacks on bottom end torque. The USIM has better low end torque than the MEVI, but many people who have MEVI's will comment they have not noticed any impact on low rev performance.

• This writeup was stolen from the Big Org and sums it all up quite nicely.

The Japanese Market Cefiro has a Variable Intake called the MEVI.

It's not a true Dual-Plane intake (like the Taurus SHO, or the 3.8 SPI from the later model Windstar/Mustang) which has two distinct air paths from the air filter to each cylinder (one long, for low revs - one short for high revs). Instead, it's a Dual-Plenum design that has a second plenum directly above the lower intake, providing a shorter path for the Dynamic Supercharging effect (described below). The second plenum is 'activated' by opening a set of butterfly valves. These valves are opened by a vacuum actuator at the appropriate engine speed.

Dynamic Supercharging is the concept that when the intake valve closes it causes a pressure wave to travel from the outside of the intake valve back towards the air filter. When the pressure wave reaches the plenum (the common part of the intake track between the throttle body and the individual runners) it bounces back towards the intake valve. If the intake valve opens just as the pressure waves gets back, then more air is forced into the cylinders and it increases the volumetric efficiency. There is a specific engine speed at which this Dynamic Supercharging effect happens, and the length of the runners changes this engine speed, because of the time it takes the wave to travel.

Intake spacers change this effect to a lower engine speed (because the wave takes longer) giving the engine more bottom-end grunt (marginally, and at the cost of mid-range grunt)

The dual-plenum design gives the engine TWO speeds at which dynamic supercharging happens - at high speed the upper plenum valves open and the shorter path to the upper plenum gives the dynamic superchargin effect at higher engine speeds, increasing breathing and prolonging the powerband.

That's it, in a nutshell.

First of all you'll need to find yourself a Manifold.

These are quite easy to purchase from New Zealand wreckers and can be purchased from around $350NZD for everything including the “Vacuum Cannister” and “Vacuum Control Solenoid” which I will explain later.

Another place which used to sell the Kit brand new is a parts store in the USA called Courtesy Nissan. I am unsure if they plan to sell it again, but is may be worth a look.

An engine with a MEVI is easily distinctive as it has a flat top and two engine covers instead of one. When I did my swap I acquired my Manifold second hand from New Zealand as Courtesy Nissan were going through a dry spell and I couldn't get a new one at the time. Here were all the bits I got for the conversion, thanks to Nissin King Partsworld in Hamilton.

Also included in this kit were two other important devices essential to making the manifold work properly.

The “VCS” (Vacuum Control Solenoid)

And the Vacuum Cannister

These two devices will allow the MEVI to activate or actuate at a set RPM, but this can't be done without the help of a RPM Switch.

The RPM Switch both “killerVQ30DE” and myself (Jordan) use is the Summit RPM Switches, and these seem to work flawlessly.

I will come back to the activation part later in this write up.

Allow yourself some time to do this as it isn't a job that can be done in a few minutes! I also recommend you purchase a Haynes Manual for your Maxima before doing this as it will show you where a lot of things are that I wont explain.

I recommend starting by removing the two bolts at the back of the USIM manifold first as you want to find out if you have a short enough socket to get the bolts off between the very short space between the firewall and the back of the manifold. If you dont have these tools, then you dont have to put the car back together again to go and buy the right tool!

After you are sure you can remove the above bolts, start by removing throttle cables, IACV plugs, EGR guide tube, Cruise Control, TB and IACV from USIM.

I'm hoping that the below photos are quite self explanatory. I am by no means an expert Mechanic, and I didn't find it too difficult to work out.

Manifold off..

My advice for putting the manifold back on - Start with the rear manifold bolts first - it will save you hassles

Ok, so now it's on. Your back aches like mad for bending over an engine bay. Pat yourself on the back (or massage it) for a job well done!

Maybe you might want to make your engine covers disgusting colours like mine…

Here is the Vacuum canister location I decided to use. I mounted mine under the engine covers and I tapped the vaccuum source off the Manifold.

• Update 30/01/09: After a couple of years with the vac can in this location, it had perished slightly. I think due to the heat off the manifold. I would reconsider this location for the vac can for its longevity.

• Update 30/01/09: Tap the vacuum off the Larger nipple on the manifold as it requires a fair amount of vacuum. It has been noted that stealing vacuum off the smaller nipple can cause pinging at low rpms - so be selective of what you're stealing vacuum from :) I didn't use a “T” adapter like everyone else. If you notice.. my canister was an OEM Nissan one with three outlets. So basically I rerouted the vacuum to its pre-existing purpose, whilst tapping it for the MEVI. There is a diagram below which shows how I did this. I have now however blocked off one of the inlets and am now using a “T”. I have found this increases the actuation efficiency.

Now to get the Summit RPM Switch to work:

Here's a pic of what my summit switch looked like when it arrived (except mine was white).

Wiring is quite simple for the rpm switch but I got stung on one thing. I thought (like most automotive devices) that the RPM switch when activated would put out +12v, instead it puts out -12v. So forget about wiring up the VCS to your nearest ground and running a single wire to the control solenoid. You will need to run both + and - to the RPM switch to get it to activate. I tapped voltage for the RPM switch from the cigarette lighter and mounted the RPM switch under the shifter cover in the centre console. You can't see it.

KillerVQ30DE mounts his right here. At least here you can easily adjust the RPM activation point if you need to.

Next is tapping the RPM source. This is generally quite easy and all you need to do is tap the “TAM” screw from the back of your tacho. You will need to refer to your Haynes Manual for instructions on this, or if you're confident enough you can just wing it like I did.

I however ran into a problem with this. I had a 1998 Maxima with a digital instrument cluster/tacho. Basically these dont have the “TAM” screw for tapping RPM source from the ECU. You'll need to find the white/green wire (ie white with green stripes) on the ECU wiring loom and tap it.

The next part is to set the RPM. My wife and I did this by going for a drive. She set the dip switches to 3k rpm. I held the rpms at 3k and she adjusted the “ADJUST” screw so it activated at that that rpm. This way all she needed to do after that was set the dip switches to the desired RPM level.

Below is a diagram of the circuit board. Please ignore the dip switch settings on this picture as I believe they are wrong. (hey.. I didn't do it!)

The ideal RPM activation level (and this has been numerously dyno tested) is 5,300 rpm. The stock Cefiro activation point however is 5,700 rpm. Nobody knows why this is, but I'm sure nissan intended it to be that way. So the choice is yours ultimately.

The below dyno graph is courtesy of KillerVQ30DE who tested different MEVI activation points.

Red line = 5300rpm MEVI

Blue line = 5500rpm MEVI

Green line = 4900rpm MEVI

I as well as many other people enjoy the MEVI. It's not too difficult to do - just time consuming. It may seem like a huge ordeal, but in the end once it's done you'll be rocketing through high rpms like it's gone out of fashion.

I hope you find this write up useful.

If you have any questions, don't hesitate to ask in our forums.