So my VIAS has been broken for the last 30K miles or so, giving me nothing for top end power, I decided that instead of JB welding the cup or what not, I'm going to inspect it ( I knew it was bad ) and if bad I'm going to remove the whole plastic piece thats inside the intake manifold that switches over between the short and long intake runners. I took off the throttle boddy to get at the last philips head bolt, took the whole diaphram assembly off the intake manifold, and I had NOTHING hooked up to the power rod inside the manifold, my VIAS was rotating as it liked inside the engine, and under constant high RPMS it looked like it was actually rotating by itself 360 deg inside. I decided, its time to experiment, having talks with Matt (SR20DEN, wossa ?) bout removing the whole switch over mechanisim and loosing low end power to gain the top end- possibly even more power with the rod n stuff all out of there. I removed the wire harness and all the hoses out of the way on the passenger side of the engine, by the little silver end cap thats right on the passenger side of the intake manifold- opposite side from the switching mechanisim. I found alot of metal chunks of the mechanisim inside the whole switchover box, cleaned it all out, and reinstalled everything back up without the VIAS crappola inside the runners. Car fired right up, and I go for a test drive, to my supprise the low end power feels more snappy and ready to go than ever before, and top end is back up again. I did a quick test on my way home on the deserted testing road by my work, and car would have a hard time accelerating past 115MPH in 4th gear, this time around it got right up to 130 without a problem in 4th and the speed limiter kicked in- ROCK ON. On the other hand I blew a exhaust manifold gasket somehow, so I'm gonna have to install my headers back up. I didn't take any pictures of the whole job, but it wasn't too terrible. Having some nice top end power is a nice feature.

 

That's the same thing I planed to do when the time come. I'am glade to see someone has done it. I myself has had that problem happend twice, and that has been about 6 months ago. Ok since then though, car only has 63k miles on it.

 

Erm, wait, I'm having trouble following this one... what exactly did you do to the VIAS setup in the end?

 

I left out the plastic piece inside manifold that runs through it, opening and closing the high RPM runners and low RPM runners, basically my intake is stuck on the HIGH runner right now, but its actually sucking from both. I was fearing low end power loss, but judgeing from my test drive, comparring it to morning commute drive with no gas in the tank, to full tank of gas on the way home after removing the VIAS switch over mechanisim- I lost no low end, even felt stronger to my butt, and top end was vastly improved ! I forgot to add that after removing the end cap on the pass side of the motor, I slid the whole plastic mechanism out of the manifold. You need to take apart both sides- as there is a spring inside the VIAS switchover mechanisim, that WILL fall into the intake if you try to just remove it from the pass side saving your self the time, of removing the switch over diaphram by the throttle body. There are no real names to these parts so, its hard for me to clariffy what I did. It would help if someone had some pics of the intake apart so I could just point my finger at the part that I removed. But I think you get the idea.

 

I removed this by the TB,


then found THIS cup inside my manifold all sheared up-



Removed a buncha BS that is in the way of this-- on the pass side of the engine,



To make it look like this....


And I left out this...



Make sure not too loose the spring that sits at the end of the shaft that slides into the cup- this is why I removed the diaphram box in picture 1, that and to inspect it too.

Sorry I didn't take pictures, I was doing some little stuff on the car, oil change, battery, A/C pollen fitlers, had some time on my hands and thought, fuq it lemme fix my damn VIAS, so no pictures where taken durring this said surgery.
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To take that out, can you just loosen the two screws that holds the shaft in place, as scene in the pics????

 

YES, but there is a SPRING in the end of the shaft-



it slides inside there, and its loose after you try to pull that power valve out through the cover you posted the pics off. The spring WILL fall out when you try to pull this whole thing out and it will be intake manifold, start the car up and you might bent some valves !



This spring is like 1" long when its not preloaded, in its free state. So this spring will rattle around in the intake manifold till it gets sucked in by one of the valves and it will bent up the valve. The valve don't open enough, nor is it big enough for it to acutally suck it into the combustion chamber- but it will make a nasty mess out of one of the intake valves.

The spring is pressed against the cup inside the change over diaphram.

 

Thanks BlackBIRDVQ, I think I better leave that alone. I'll have my local shop do it for me.

 

I think MaxGator did this also a while back. he removed the power rod. he said he lost torque before the switch but his peak gain was at 221 whp with just a y-pipe/exhaust/cat-back. Im surprised you didnt lose any tq; it was that reason alone i decided to just fix the unit instead of removing the power rod. Can you dyno ur gains? i know you gotta lot of mods and would really enjoy seeing what you gained from all of this

 

we had a local guy that sr20den removed the power valve from. he is a 3.0 5spd. he had just dynoed and found his top end to be lacking as well. he dynoed after taking the valve out and made alot better hp numbers but his toruque lost around 15lbs just about everywhere.
matt and i opened my manifold and found the cup on the verge of breaking loose so i we did the jb weld deal. nathan ended up putting his repaired cup and valve back in because he said the low end had suffered too much. it is a possibility that there were other issues with his car hurting his low end but i could not say for sure.

 

BlackBIRDVQ- any chance of getting some dyno runs in? it would be great to compare to nathan's graph.

 

Hopefully next week I will dyno, I need to get a before n after of the Cattman Y vs the HS headers.

 

BlackBIRDVQ: As far as I know, in "high-end" mode, the ports pull air from both the low-end runners and the surge tank anyway, so you've basically done what SR20DEN did to (can't remember who... max_gator?) one dude's car--keep it in a permanent high-end mode, but a little better. You should gain high-end over the stock setup since you've removed the valve (which can act as a restriction), but low-end torque was most likely lost, if you even care

 

Nah, it wasn't me. I was one of the first to have a problem but Nissan swapped (eventually) my intake - but wouldn't let me have it to play with.

I'd like to see the dyno comparison too.

Blackbird's butt dyno may be better than mine; my **** has a hard time being real accurate.

 

mad2max... i had to look up under the old VIAS fix thread

http://forums.maxima.org/showthread....2&page=1&pp=40

 

Doesn't the vais also help with fuel economy on the low end? Anyone notice any diff with mpg's?

 

midrange power and low power is kinda lost, but a over 5500RPM car just rocks HARD. I find myself hitting the rev limiter more often than I ever had. I wonder what a raised rev limiter would gain me. Dyno will follow.

 

I'm pimpin' my VIAS summary, full time.

Go here, page 5: http://members.cardomain.com/mhadford

 

I took my VIAS apart and it doesn't have a spring, will that create a problem? I could just buy a spring from a hardware store and it would be fine?

Mooney

 

Yes and Yes. I hope

 

Thanks. Just got back from Lowe's purchasing an assortment of about 100 springs, maybe the right one will work. Probably shoulda asked first, how stiff is the spring, the spring rate?

Thanks,
Mooney

 

Thank you for making all this talk so simple.
I think mine does not work as my friend on his 99 shows same prefomance then I do on my 2000.

I will look foward to fixing it.