3.0 people, who has removed the VI valve/flap in the UIM?

Ive read a few threads about just a couple people who have done it, a long time ago, but nothing saying that this is something that should be done.

This valve engages at 5k rpm, and you can really feel the difference than before 5k rpm. Well, what happens if the valve is open all the time or just removed?

Just curious if anyone has done it, before I go in and take it apart, being that mine works fine.

 

Ive read that you lose a pretty good chunk of low end in exchange for more top end. Although I haven't seen any dynos reflecting this.

 

If i'm not mistaken, you can just tie it open to get a general feel of what it will be like. I personally wouldnt do it unless your planning on extending the rev limiter.

Someone correct me if i'm wrong though. Dont wanna spread misinformation.

 

I got an EU Just need to get a harness made and a wideband

 

I've got an extended rev and I'm thinking about doing this.

My logic is. Low end torque only really really matters in first gear and my car can destroy the brand new Kuhmo ASTs from a roll in 1st.

But if its really gonna let the engine breath between 5,200 and 7,200, I'm down to do it.

I got a question about this though, what position (ex; o'clock/degree) should the rotating cup be when it's closed? How about opened?

EDIT Can someone confirm this, but I'm sure you can make up a partial chunk of low-end loss by dialing in the ignition timing?

 

I plan on doing this to sacrifice low end. With mods im sure ive gained a bit of low already and well having too much on fwd is not really a good thing unless you really want to kill your tires. Plus my rev limiter is bumped, hopefully the tune will fix the 7200rpm hiccup

 

I've done this multiple times and its fun for a while on the highway. Low end isn't completely gone, but something is definitely missing.

Not worth it unless you have it all tuned up and an extended rev IMO.

 

yeah, i wouldnt do it unless you extend that rev and actually use your top end. example, i like to run the 1/4 mile. with my extended rev, i never fall below 5k rpms on the track, so that extra power is useful. whereas id only be using that low range power on the launch through 1st gear. so its all about where you need it. but from my research on here its a pretty nice gain with it removed actually. theres a few old threads showing whp/wtq differences between the two options.

 

Anyone?


I plan on doing this now for sure once my EU is installed and especially when my S/C is installed

 

The loss in low end comes from the loss in velocity of the air equating to a loss in momentum. The moving air has a force associated with it that forces it into the cylinder. Once the velocity of the air drop off, at low rpms, the momentum is reduced resulting in a reduction of this effect. This applies only to a manifold that only has one shape

To keep the velocity of the air high at low rpms the DEK maifold takes one shape. Once a predetermined rpm is reached, the air is flowing so fast that negative pressure is building, and the manifold changes shape, lowing the velocity of the air to a more reasonable level, thus reducing the negative pressure. All of this only applies to an NA motor. Once you go forced induction, the momentum "ram air" effect is overshadowed by the positive pressure created by the blower.

However, if you are going to get an EU an up your rev limit, the "open" position of the DEK manifold, for high rpm (above 6500), might not flow freely enough as it could without the power valve. Once you are running with the extened rev limit, though, you should never need to drop to an rpm where having the valve closed would be beneficial, unless starting from a dead stop.

My recommendation, for the street, leave the valve in unless you go with a force induction solution. For the track, where the RPMs will always be high, you might want to remove it.

Oh, and I'm sure you can gain some of that low end back by tuning the timing, but it will never be as high as it was with the power valve closed because you are lacking the advantage of the faster moving air in the manifold at low rpm.

 

Interesting explanations ! I' ve been thinking about this for a while, because I will have to break in my freshly built VQ30DEK, I will leave the swirl valve for the break-in period and once the blower get in it's going to be bye bye swirl valve.

Thanks for the explanations.

 

i just removed this a couple of days ago and i don't have and extended rev limit or any tune or a supercharger.... and to be 100% honest i cant even really feel a difference in the low end torque or the high end....so id say the losses or gains from doing this have to be real minimal...id like to see a dyno pull with and with out the rod to see what it actually does for improvements and losses...

 

this would be great to see..

From teh other threads I have seen, I have not found any dynos

 

Butt dyno doesn't tell you much. When I shift at 7,xxx the RPM never drops below 5,xxx so I'm gonna give this a try. I tuned my ignition timing a little bit and I have a lightweight flywheel so I can shoot into the high revs with teh quickness

 

Can you find a thread or two please?

 

http://forums.maxima.org/all-motor/3...e-removed.html

 

http://forums.maxima.org/dyno-discus...lt-dyno-2.html