When your car is at idle and you got the hood popped. Do you hear a tapping sound. My VI makes that noise. I believe its the butterfly valves since I can pull the actuator arm back and it stops. Like they are flapping around or something. I took it apart and it all looks good. Does anybody else's do that?

 

No tapping here.

 

Iilacs taps, mine doesnt. When we touch the part where the actuator connects to the butterfly rod assembly the tapping stops. I believe it might be because theres too much clearance between the rod and the holes in the manifold so it vibrates.

 

My VI taps once in a while. I could barely hear it.

 

No tapping here. Do you think that if the butterfly valves were not shut properly it would disrupt air flow at low rpms and cause a power loss?

 

I30tmikeD: i would say yes because the air travel is greater, but the butterflies are designed not to close 100% bc then that top plate area wouldnt become pressurized and you need that area to be pressureized to give that "jolt" of power upon the activation of VI....


BTW no tapping here did u install the rubber gasket in that hole in the VI where that rod comes out?

 

I didnt do the install of the VI itself, I just put it on my car. What side is it on? , and what will I have to take out to look?

 

oh ok...u wont have to take anyhtign off just pay attention listen by where the actuator meets the rod u migth hear it there , but the rubber piece should be insdie the hole where the rod leaves the VI

 

I heard someones VI tap and he does have the rubber seal thing installed.

 

Any way to stop this?

 

wild guess is to take off the butterfly valves and screw them back on all in the same side since they are chamfered on one side and sharp on the other. Its really a wild guess but maybe that sharp edge is causing air turbulance and vibrates it?

 

Mine taps and I have the rubber seal installed. I have no clue on why mine taps but I feel the mevi kick. At first, I thought my butterflys were loose so I loctite it with red and the damn thing still taps. Like Nismo said, If I hold the butterfly assembly, it stops tapping. The butterflys close properly and open properly so I have no clue.

 

how tight are the butterflies/rod when in a reg state(not activated) ... maybe the whole thing is moving ,, i forgot how the MEVI was assembeled but maybe the "spring" mechanism isnt tight enough to hold the rod securely... but i dotn recall how the rod is kept tight until activation? ill check my set up and re post later

 

Wayne please check your email!!

 

the spring in the actuator is plenty strong to hold it shut. There can be alot of slop in the plastic linkage though so it can be a number of things that causes it to tap and rattle.

 

I was pretty **** about making sure the MEVI was assembled with the beveled edges down on the butterflies.


And of course I loctited it.

 

That's an unusual theory. Who told you that?

 

Just make sure those screws are on the butterfies good and tight. Whe mine was on I heard a little tapping to but it was very faint.

 

no one told me that ..ive gatherd that from my expierences with the VI and looking into the way it works... why is it a good theory or bad or misinformed? if im wrong please correct me.. i would be interested in other peoples ideas

 

Its not completely sealed up top I dont think.

 

oh yeah i know it isnt sealed ,,,, im saying it shouldnt be ...

 

Sorry to take so long to reply.

You are right that pressure is involved, but it is not a static pressure that accumulates in the plenum above the butterflies, rather it is a dynamic, or moving, pressure wave that travels back and forth in the intake runners.

The pressure in the intake runners oscillates because of the opening and shutting of the intake valves. The air next to the valves pressurizes when the valves close, due to the momentum of the column of air in the runner. The pressure builds up and then travels backwards away from the valve.

As the pressure buildup travels away from the valve, the air next to the valves reduces pressure, so in effect there is a pressure wave that travels away from the valves and backwards towards the throttle body. The pressure wave will eventually bounce off the back of the intake manifold where the individual runners begin.

The pressure wave will then travel forward toward the valves again, and if the speed of the pressure wave is just right, the pressure wave will hit the valves just as they are opening, creating a ram air effect that increases the volumetric efficiency of the engine.

This only happens at a particular rpm range, though, and is determined by the speed of sound in air (which depends on air density), and the length of the runners. Long runners will be most effectual at lower rpm, when the time the pressure wave takes to come back to the valves is relatively long. At high rpm you need short runners to decrease the time for the pressure wave to echo back.

What the MEVI does is allow for a shorter path for the pressure wave by allowing it to bounce off the upper plenum when the butterflies open at high rpm.

Unfortunately, although the MEVI does a good job at high rpm, something about the design makes it work not as well as the USIM at low rpm.

 

[QUOTE=Stephen Max] [QUOTE]




u know that feeling where u cant explain something, but it works in ur head... thats how i felt.... but wow that description was perfect! may i ask where u acumulated that information... i 100% agree with u!

 

[QUOTE=DaThrillr][QUOTE=Stephen Max] Thank you. I read a lot. A degree in mech engineering and experience in dynamic systems helps.

 

great writeup