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Discussion Starter · #1 · (Edited)
OK. First thing I want to say is this mod is not for everybody. That now aside, let me explain for those that don't know what I'm talking about. VIAS=Variable Induction Air control System. This is the butterfly that is in the front of our intake manifold and is designed to give good lowend power and good upper end power by opening and closing this butterfly at different points to maximize power and airflow when needed. This butterfly is also part of a shelf in our intake manifold. This shelf completely separates the left and right runner ports. When the butterfly opens, it allows airflow between the left and right cylinder banks.
Well, I have been doing a lot of thinking about alternative intakes or modifying our intakes for better flow. So after doing a lot of research on this forum and many other VQ forums, I discovered that some other VQ engines have been deleting their VIAS with documented gains. Generally, the results have been showing gains un the upper end and some loss on the lower end.
So about 1 month ago, I completely removed the butterfly and it's surrounding housing from my VIAS, leaving nothing but the base, reinstalled it, and have been running around testing it out. My butt dyno was backing up what the other VQ's were saying--a nice gain on the top end and a bit of a loss on the lower end.
Well, I finally got my truck back to Uprev to get dynoed again, and tweak the A/F a little to correct for the changed airflow. The runs went well, not quite as good as I hoped for, but not too bad. Now this run was done on the same dyno, by the same operator, so I tried to keep things as consistant as I could. Only main difference is today I ran in 98 deg weather and was getting pretty heatsoaked vs last time I dynoed on a cool January day. Uprev did the graphs in SAE to try to make up some for the hot day, but they said it might not do enough. Because of the weather, I would say my results today would be worse case scenario gains.
Anyway, using my final run from my January cam tune vs todays Vias delete tune, I ended up with a peak gain up 9whp and a loss of 2ftlbs. Now gains at certain points were 15whp and 12ftlbs. The loss occurs from the 2300-3800rpm range and is fairly significant at its peak I admit. And the reason I actually have a slight peak loss in torque even though I have gains 2/3's of my rpm band is that the my previous peak was in the 3300rpms range-right where the Vias delete hurts you the most. So what I ended up with is a gains in both HP & TQ from 1500-2300 & 3800-6800rpms. Again losses were from 2300-3800rpms. It's a give and take.
Anyway, from my personal experience driving around for a month, even pretuned, I love the mod. Under good throttle in lower rpm range I can feel a power loss and while cruising at low rpms on the highway, i could also feel a slight power loss. To me they were both very slight. As for gains, my truck now pulls very hard from 3500 all the way to 6800K. You can really feel the difference in power when you get on it.
For me and my style of driving, this suits me well. It also works well with my cams which also love the upper end. And for the track it should be great. I will only be in the 2300-3800rpm band for about 1 sec in 1st gear and from there on I will be 4K+ which is were all my gains are.
Now for other VQ owners. I think generally the heavier your truck is, such as off road modded 4 x 4's, this mod would not me a good idea. Also for automatic owners, this mod would have it's downfalls, since your transmissions like to keep you generally in the power loss range. As for the average 6-spd or even heavily modded automatic, this is a mod worth considering. It really boils down to your driving style. But the gains are there for the taking, and best of all these horses are FREE!!!!!


 

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Thanks for the info. I remember back in the early days of modding these motors when we had nothing. I mean NOTHING. Will of WRP was the only guy offering anything for us. This topic came up but nobody stepped up to test it and find out. Thanks Rodney for doing it. Good info.
 

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Discussion Starter · #3 ·
I've really been wanting to post up about it for some time, but I really wanted an Uprev dyno to backup the gains I thought I had gotten. I saw a few times looking back on this forum that the VIAS was experimented or questioned, but at the most, people only blocked it it open. In fact the Aaron guy with NWP that was trying to get intake spacers made for us, was actually the company making VIAS block plates for the vq35 Maxima & Altima guys. And as a note, due to the unique design of our VQ40 VIAS design, a block plate would be difficult to design, and is possibly why he didn't push it on us. Anyway, To my way of thinking, there should be no or little gain in just blocking the VIAS open. You would lose your usual lowend power but the upper end I think would stay about the same since it is usually open on the top end anyway. Removing the entire butterfly and its housing opens up, I would say, maybe 1.75 times as much opening for more airflow. The other thing I noticed also was that when the butterfly is still installed, even when it was open, it partically blocks the 1st two intake ports. So for me, the removal was the only logical test for its possible gains. And I do want to thank shinermiller for helping me research and experiment with this mod. He has been trying his out blocked open for several weeks. His gains appears to be similar to mine via his butt dyno, but probably less loss and gains do to the VIAS still being in the intake. He did say with his auto 4 x 4, the lowend loss was sorta annoying.
 

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Nice post, thanks for the R&D!
 

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Awesome info. Though not really what im looking for. I want TQ more than HP. Great that guys who know about these things are doing some research and testing. I would love to be able to contribute to good unique mods like that.

rdrfronty: You and Shiner keep on doin your thing with the mods! I pretty much look to your trucks when im curious on mods. I have a spare motor kicking so if either of you guys ever need cheap parts for research, that are on the motor let me know. Not That there's really that much worth modding on it aside from the intake. Would be happy to help though.
 

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Discussion Starter · #6 ·
VIAS Delete-how to guide

I thought I would add this info on doing this mod if anybody decides to give it a try. Mechanically swapping the VIAS is very easy. Deleting it is also easy, but takes a little work to get the heavy duty plastic cut/ground off smoothly. The complete vias consists of the butterfly valve, its surrounding housing, and the base that seals off the intake once its installed. You have a lever that protrudes from the base of the vias, which also sticks out side of the intake. When this lever moves, the vias butterfly opens or closes. We have a power valve on the outside of the vias that attaches to this lever. It is controlled by vacuum and is also monitored electronically.
So to do this mod I basically just ground off the entire vias butterfly and surrounding housing, leaving nothing but the base. I used a grinder to do this. The problem when doing this is it creates 2 long grooves and 1 hole in the base that has to be sealed off or it will have a massive vacuum leak. I personally used black high temp rtv and it worked great. A good epoxy would be a good alternative choice. As for the power valve, vacuum hoses, & wires--I left everything just like it was with the exception the power valve that I just didn't connect to the VIAS lever since it is now gone. I didn't want to take a chance of getting SES codes, so thats why I reconnected everything. Plus the dealership would have to look close to notice any difference.
The actual mechanical work goes like this--
1-remove intake tubing if you have the stock tube
(with my volant, i didn't have to)
2-remove engine cover
3-remove hose from top side of throttle body
4-remove 2 bolts(torx) attaching the power valve to the vias base
5-gently pry the power valve off the vias lever with screw driver
6-remove 2 bolts(torx) attaching the vias into the intake
7-gently pry/pull the vias out from the intake
8-temporarily remove o-ring from vias
9-cut/grind the entire valve and housing away, leaving just the base with the groove & lip for the o-ring
10-use rtv or epoxy to seal holes in the vias base
11-once dry, reinstall o-ring
12-reinstall vias base into intake using 2 bolts(torx)
13-reinstall power valve onto vias base using 2 bolts(torx), note that the valve doesn't connect to the lever & it still operates just fine to help prevent SES codes.
14-reinstall hose on the throttle body
15-reinstall engine cover
16-reinstall intake tubing if needed
17-start engine, check for vacuum leaks
18-Now start burning rubber!!!!!
Now for any reason somebody wants to try this mod, but decides later it's not for you it's not that big of a deal. A new VIAS butterfly can be purchased new for about $60. You can also often pick up a complete used intake from $50-100. Also as mentioned before, while a block plate looks like a easy logical choice, the design of our vias and intake makes that not an option. Our VIAS base inserts into the intake and is internally sealed. The only other option would be for a machine shop to creat an aluminum copy of the base with seal groove and all. That would work fine.
One more note. If anybody starts researching VIAS more, you will likely see another mod called SSIM. This basically is a related mod, but goes one step further by removing the entire intake shelf. From my research and from the results of my dyno, I'm thinking this would be going too far. It might give a tiny more topend, but I think the low end losses would be massive. But I might be wrong, who knows.
 

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good stuff RD, thanks for posting up the info!!
 

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The other thing I noticed also was that when the butterfly is still installed, even when it was open, it partically blocks the 1st two intake ports.
if I recall correctly alot of people were showing a lean condition on one bank of cylinders, does this correspond?
 

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pretty interesting how it flat lines pretty good right at 5400 or so - any idea's there?
 

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Back when we first starting looking at this (wrp) I drove with mine open(just block off the vacuum to thwe valve) and I didnt like the around town loss. It became more doggy for sure. So everyone remember Rodney is lightweight 2wd, and stick. that makes a BIG difference on what can be tolerated vs More weight and/or 4x4 and auto. While once you go all the way there no tunring back cheaply. if you want to check out the throttle response and power down low where it was designed for. Unhook the vacuum hose and plug it then drive around and see if you can tolerate it on the lower rpm. if you can then you do the full mod. Just smart money says dont go all the way upfront
 

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I know this is probably a stupid question but could you perhaps cut some slots out on the butterfly instead of completely removing it? I guess either way I suppose you'd lose some lower end and not gain the top end but I was just curious.
 

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Discussion Starter · #12 · (Edited)
Back when we first starting looking at this (wrp) I drove with mine open(just block off the vacuum to thwe valve) and I didnt like the around town loss. It became more doggy for sure. So everyone remember Rodney is lightweight 2wd, and stick. that makes a BIG difference on what can be tolerated vs More weight and/or 4x4 and auto. While once you go all the way there no tunring back cheaply. if you want to check out the throttle response and power down low where it was designed for. Unhook the vacuum hose and plug it then drive around and see if you can tolerate it on the lower rpm. if you can then you do the full mod. Just smart money says dont go all the way upfront
I totally agree with Brutal on this. If you disconnect the VIAS you can get a pretty good idea what type of losses you will see in the 3-4K range. Only problem though is that you cant see what type of gains you will see up top that way. The gains can't be found until the entire VIAS is gone, blocking it open isn't enough. But still, if you can tolerate the lowend, I promise you will love the topend if you go all the way with it. Again it boils down to driving style, truck weight, and transmission. Light weight, manual transmission, and lighter trucks will be the ones that will benefit the most from this mod.

pretty interesting how it flat lines pretty good right at 5400 or so - any idea's there?
As for the flat lines. Our engines all tend to do that on top. Mine just happens to carry the power longer in the rpm band so its more noticeable on my dyno. Most VQ40's only flatline from maybe 5300-5800 than drops. Mine flatlines from 5400-6300rpms. Not sure why we all do that.
 

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Discussion Starter · #13 · (Edited)
if I recall correctly alot of people were showing a lean condition on one bank of cylinders, does this correspond?
Well, the butterfly partially blocks the front cylinders from both banks. So I don't think the VIAS is why we might have lean condition on one bank vs the other bank.
 

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Discussion Starter · #14 ·
I know this is probably a stupid question but could you perhaps cut some slots out on the butterfly instead of completely removing it? I guess either way I suppose you'd lose some lower end and not gain the top end but I was just curious.
I don't think that would be enough difference in airflow to make much difference. The butterfly itself is roughly about the same size as our throttle body, appx. 2.75". The entire butterfly and housing is appx 3.75". With just the butterfly open or removed that gives you about 5.9 sq inches of airflow. With the entire VIAS gone it gives you appx. 11 sq. inches, almost twice as much flow. Plus again when the butterfly is still there, when opened, it stands vertically maybe 2"-3" or so in front of the first two cylinders, one more than the other though.
 

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Well since you saw gains from this mod, I went ahead and started the process. My low end isnt really that bad but my top end sure does feel alot smoother and quicker.
 

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My opinion is that removing the VIAS enhances the performance of all the relative modifications to there peak performance thus making more power. Also with out the VIAS in the manifold air flow does get increased.
 

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As for the flat lines. Our engines all tend to do that on top. Mine just happens to carry the power longer in the rpm band so its more noticeable on my dyno. Most VQ40's only flatline from maybe 5300-5800 than drops. Mine flatlines from 5400-6300rpms. Not sure why we all do that.
I'd guess it's a little extended because of your cams. In any of the race engines I;ve built or seen or dyno'd, they flat lined like that simply because either the exhuast or intake (runners in the head, intake runners, intake runner length, ect) were becoming a restriction.
 

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So how can we un flatline them?
 

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So how can we un flatline them?
engine dyno, time and money???

LOL

I mean, it depends what the issue is... There is no straight answer. A change in the profiles to the cams may help, changing the scavenging effects of headers... I mean I would tend to think this is probably more on the intake side personally, but I've never seen the intake base apart... I'd have a hard time blaming the heads since 4v heads flow usually really well.

I mean all engines do end up flat lining, what surprises me is how soon they do in the RPM range... I would have thought that these motors would be pretty happy to rev past 5500...
 
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