[twowheelin]

The VIS system on the 2.3L intake is helpful in smoothing out the torque curve, but its does not improve torque at any point. Please see the vis dyno info here. Here is a simple, low cost, and reversible mod to run your intake with the VIS system deactivated. This will operate the intake with the 'short runner' air path normally used only during high (4500+) RPMs. Here are the basic steps for this mod that can be installed or reversed in less than 5 minutes.

Materials required:
- 2" length of 1/8" vacuum hose from AZ, Pep Boys or similar.
- 1 plastic golf tee: Cut off the top third, leaving just the pointy part.

1) Remove the engine 'beauty cover'

2) Find the VIS solenoid valve located on the intake manifold on top of the cylinder #2 main runner.
[attachmentid=1977]

3) Pull the outlet hose off of the VIS valve.
[attachmentid=1978]

4) Install the 2" length of vacuum hose onto the VIS valve. Plug the loose end of the hose with the golf tee point.
[attachmentid=1982]

5) Attach the loose VIS hose (removed earlier) onto the end of the golf tee. The only purpose of this step is to keep the loose hose from flopping around and preserve a 'stock' appearance. (Gotta love a stealth mod. )
[attachmentid=1983]

Butt dyno testing seems to confirm what the dyno chart shows. The typical boost at around 3K seems to kick in a little earlier and the engine pulls a bit stronger throughout the midrange. I can't say I've felt any drop around the 4500 RPM mark as shown on the chart, but I've got a few other intake mods that may be helping to minimize this weakness.

 

[Da 6]

VIS=VILM? does this take place same time as VTCS of VVT. You disabled VTCS as well right?

 

[twowheelin]

Originally posted by da 6@Feb 18 2005, 12:35 AM
VIS=VILM? does this take place same time as VTCS of VVT. You disabled VTCS as well right?

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Yes, VIS is basically a Mazda implementation of VLIM. My VTCS is stock now. I did unhook it for awhile, but found it stayed open all the time once the engine was at normal operating temps, so no real gains once the engine was warm. (Need to pull the butterflies completely out...) I believe VTCS is supposed to open fully at 3750 (when cold) I think VVT varies depending on multiple conditions. The VIS change over is complete at 4500 according to Stretch's intake article on 6tech. (My most used bookmark )

 

[MrTea]

any follow up on this? i'm sure it's an easy one to try if nothing else, but what are your feelings on it? you keeping it this way or just changing back as not seeing an improvement? any updates would be great!

 

[twowheelin]

No complaints or problems. I reversed the mod and went back to the stock setup earlier today as an experiment and the car felt sort of sluggish compared to what I had gotten used to. I also noticed the car sounds a little quieter and higher pitched in the normal intake config. (i.e. slightly lower and louder with mod in place) I am putting the mod back in before heading out tonight. :yesnod:

 

[Junqueira]

Does anyone have dyno with and without VIS please. Link in first post doen't work already.

 

[Merey]

Sorry for my English in advance! (from Kazakhstan)
i have problems with solenoid valve on the intake manifold (i will buy it tommorow). So in your post u wrote about disconnecting/switch offing those valves. Please answer to my questions. After disconnecting, the car became faster? You switched off both of valves or only on the 2nd cylinder.
thank you in advance!

 

[Junqueira]

Sorry for my English in advance! (from Kazakhstan)
i have problems with solenoid valve on the intake manifold (i will buy it tommorow). So in your post u wrote about disconnecting/switch offing those valves. Please answer to my questions. After disconnecting, the car became faster? You switched off both of valves or only on the 2nd cylinder.
thank you in advance!

Hi,
a solenoid fitted on 2nd cylinder is for varriable intake length. Inside of plastic intake manifold is a flap and according to vacuum it switch between shorter or longer air channels to cylinders. This is for "smoother" torque curve. If you block a hose according to this guide, you'll fix flap in short air way. So you can let connected your current solenoid like a fake for ECU.
Many cars don't have this unneeded two air ways.
By this modification, you can notice better engine performance over cca 3000 rpm.
On the 3rd cylinder is solenoid for VTCS flaps. They are somenthing similar to swirl flaps, mainly on diesel engines.

I have now instaled a Cosworth copy intake manifold and there are no flaps and my car run like a rocket. I let solenoids connected for ECU in order to CEL doesn't light up. They are connected electrically only, no hose came in or out.

 

[Merey]

Hi,
a solenoid fitted on 2nd cylinder is for varriable intake length. Inside of plastic intake manifold is a flap and according to vacuum it switch between shorter or longer air channels to cylinders. This is for "smoother" torque curve. If you block a hose according to this guide, you'll fix flap in short air way. So you can let connected your current solenoid like a fake for ECU.
Many cars don't have this unneeded two air ways.
By this modification, you can notice better engine performance over cca 3000 rpm.
On the 3rd cylinder is solenoid for VTCS flaps. They are somenthing similar to swirl flaps, mainly on diesel engines.

I have now instaled a Cosworth copy intake manifold and there are no flaps and my car run like a rocket. I let solenoids connected for ECU in order to CEL doesn't light up. They are connected electrically only, no hose came in or out.

To improve acceleration, i have to muffle the solenoid on 2nd cylinder. What about another valve, do not do anything?

 

[Junqueira]

To improve acceleration, i have to muffle the solenoid on 2nd cylinder. What about another valve, do not do anything?

Yes, I noticed a better acceleration on 5th gear for example. I tried it on various driving condition, and let it fixed on shorter way till I switch to Cosworth intake manifold. Try it and you'll see ;-) It's almost for free. I blocked a hose by a pin for a rack (http://www.pemaslovakia.sk/files/kolik 0,5.gif)
A solenoid on 3rd cylinder is for VTCS (swirl flaps). They are open for most of the time. They are closed on cold starts only. They are there for better emission on colt starts for better fuel atomization. Once the engine is warmed up, they switch to open position. But they are also air restrictive.
Before I switch to Cosworth intake manifold, I fixed them in open position all the time. They are on the end of intake manifold in front of fuel injectors.
You can see them in this video: