I have a MEVI installed and I love it. But I don’t really understand why it works the way it works. By my understanding of a true VIM, it has 2 runners to each cylinder. One short and one long. The long runner is for lower speeds and the shorter runner is for higher speeds. This way it maximizes the torque throughout the entire speed range. Maybe it's just that I have my MEVI hooked up backwards, but with the way a true VIM works and the MEVI trying to mock a true VIM, wouldn’t it seem that you would have the MEVI open in lower speeds/rpms to imitate the longer runner effect and have it closed in higher speeds/rpms to imitate the shorter runner effect?
Or does having it open make it act like a shorter runner?
If you can enlighten me on this subject I would appreciate it.

 

at lower speeds the incomming air is stopped by the closing of the intake valves, the air then creates a pressure wave that travels back through the intake runner and then bounces back towards the valve side once it hits the back wall of the manifold (near the firewall). At higher speeds, the butterflies of the VI open and the pressure wave travels not all the way back towards the firewall, but only up to the resonance chamber of the VI. This is a much short path and allows the air that is bouncing back towards the valve to arrive sooner than if it had gone all the way back down the full runner. When it's timed just right, the bounced air helps cram more in when the valve opens. I hope that makes some sense. I believe it's called resonance tuning and there was a good article in SCCf a few months ago. Enjoy!!

 

Yours works everytime? Have you driven the car, stopped it and then tested it in neutral to make sure that it is still working? I have a thread started right now because it doesn't seem to be working all the time... the valves have worked in neutral a few times but not at most other times.

One question that I have is, did you ground your solenoid as well as rpm switch to the same spot?

 

Your solenoid should only have 2 wires. One goes to the battery and the other to the harlan. The harlan has a wire to a power source, a coil, the solenoid, and a ground.

Mine works everytime! Hope I helped but probably not.

 

http://forums.maxima.org/showthread.php?threadid=217001

 

One question that I'm pretty sure hasn't been answered before is why the the MEVI causes a loss of low to mid-range torque. People keep saying that it does, but what is the mechanical (physical) cause for this. Someone please show me the light. If this HAS been answered before, then .

P.S. Can't search.

 

^^^^^

 

I would guess that there is turbulence caused by the butterfly valve chamber. This turbulence takes away some of the US-Spec VQ's low to mid range punch. Believe me, there is less power there. You can feel it and you can see it on the dyno.


Dave

 

Butterfly valve chamber? Isn't this chamber blocked off by the butterfly valves when they are closed? Where can I find a detailed assembly drawing that has a section cut-out to show the internal workings of this? And I was also wondering how the MEVI would compare to an Extrude Honed USIM. If you bore and smooth out the intake tract, it engine should be able to pull hard to redline, regardless of the length of the intake runners. Has anyone tried this?

 

Compare the 5th gen Maxima to the 4th Gen with a VI(M). The 5th gen has 2 distinct intake runners, a long one for low rpm operation and a short one for high rpm operation. The MEVI has neither. Rather, the "pouch" in the MEVI makes the long runner act as a short runner at high rpm volumetrically. A trick of physics. As a result of it's a compromise, it doesn't operate as well as the 5th gen true dual VIAS system, hence the loss in performance at some point. The MEVI is not a dual intake runner system.

DW

 

Thanks for clarifying. Now how much sense would it make to Extrude Hone a USIM intake manifold and how would it perform compared to the MEVI. If the airflow in the Extrude Honed USIM would be laminar (free of turbulant airflow) then would it be possible to see good high-RPM gains without the mid-range loss associated with the MEVI. Im sure this has been considered before. Excuse my babbling.

 

I beleive Keven97SE has done all that, and he concluded that the MEVI is stilll better. The consensus is that the MEVI places the VQ's torque in the high rpm range, which translates to greater top end HP. VTEC works pretty much the same way mathematically, with better results, too.

DW

 

Hmmm which solenoid do you have? I bought the GM solenoid. There are 2 wires... one goes to the RPM switch and the other one goes to ground.

Then there is one hose that goes to the vacuum canister and one hose that goes to the VIAS actuator. The silver nipple is vent on the solenoid.

 

I have a solenoid from a pulsar. One wire goes to the harlan for the signal, the other wire goes to a power source so that when the solenoid gets the signal it has power to activate. I would imagine all the solenoids would work the same regardless of who made it. If you have the second wire going to a ground where is the solenoid getting power to operate from? The solenoid shouldn't need a ground. Just power and a place for a signal.

 

Do you have a relay? My GM map/baro solenoid has 2 wires... and then the power and ground.

- I have the power going to the 12V positive terminal of the battery
- I have the ground going to a grounding source
- 1 wire goes to the RPM switch
- Another wire goes to the relay

 

The MEVI alters the resonant frequency of the air path at high rpm to enhance engine breathing, while an extrude-honed intake improves breathing by removing resistance to flow at all rpm, but does nothing to address resonance. Org experience indicates that the MEVI does a better job at high rpm.