I've always been under the impression that the Variable Intake was designed for more horsepower (highend, WOT, etc) but its not! Its designed for torque.

I was really confused when I first took off the plate, but then after thinking about it, it makes tons of sense. See longer intake runners means more low end torque, but less high end. Now Shorter runners mean more high end but less low end (if too short, no low end). Now when the Power Valve (Variable Intake -sorry I should get in the habbit of calling it the Power Valve) is on, it seperates the upper and lower intake runners, making them longer, therefore more torque

Now Heres the one thing I want to find out for you automatic guys... Are your intakes designed with the hole in it where our butterfly plate is, or is it just a solid runner upto a few inches behind the throttle body? If you have the hole like ours, your not missing out on any high end, but you might be missing out on a few extra lbs. ft. or ponies if you did have the VI. If its solid where our butter fly plate is, you might be missing on some high end, but judging by Aarons porting results, I dont think it would be that much of a problem.

Now going with this thought, why didn't Nissan just make it work like the VTC's? going off of the little LED we installed in DaveBond007's car (and my own, but mine isnt working right now ), the VI only really flickers on and off, it doesnt really stay activated for long periods of time. I would think they would want to keep the 'longer runners' until say 3000rpm or so, then switch over and have the plate open up. There must be something else behind it. I'm still trying to figure it all out, and please correct me if I'm wrong about something.

Here's a page with a bunch of pictures
http://garage.digitalbeta.net/intakes/index.html

Variable Intake OFF -Solenoid Off, not letting any vacuum pass threw:


Variable Intake ON -Solenoid On, letting vacuum pass threw:


With the VI Off, it lets the upper runners (cylinders 2, 4, 6) share air with the lower runners (cylinders 1, 3, 5). With the Variable Intake On it blocks the passage and creates 2 longer runners.

Here are the pages from the FSM explaining it:
http://garage.digitalbeta.net/intake...powervalve.JPG
http://garage.digitalbeta.net/intake...owervalve2.JPG

What do you guys think?

 

I'm curious... why isn't this an option for automatics??
(oh, and Happy New Year, Shawn...)

 

Thanks G! hehehe

And I dont know why it isnt an option, but I'm trying to figure out if it would even be a good idea for you to switch.

I do know that if you were to, you would not want to set it up like a 4th gen (they have it so it opens at say 5500rpm). In our case you would want it to go from idle to say 3000rpm

 

i still have my auto non-variable intake on my car, i have yet to swap over the VI since i was 5sp

good topic as ive always wondered exactly how/why this thing worked and why it never came on autos

once my clutch issue is resolved 100% (which im working on now obviously ) ill probably get to work and swap the VI on and i can post my feedback on non-variable vs variable


ps shawn resend that long PM that you saved, as ive made some room in my inbox

 

resent, lol, I just copy and pasted from word.

 

Well, this is something I plan to do in the short future. If you simply read the FSM, it tells you the VI is designed to help low end power. Then after 3 or 4K, it's just like my regular automatic intake.

 

but what does the regular automatic intake look like? lol

I've been thinking about drilling out those "freeze plugs" and taking a look.

 

Oh I dunno exactly since I've never cracked open my intake. I would imagine that the auto is just like having the power valve signal always OFF. So our top ends are the same, but the low end is better on the VE 5spd. So instead of that plate being there, it's just an empty space.

 

shawn IIRC it's not the runner length that affects the low VS top end in this case (although longer runners are for more top end)
It's the open plenum VS split plenum that does.
Think about it this way:
Edelbrock performer intake = idle to 5500 rpm (short runners seperate plenums)
Edelbrock Victor intake = 3500 to 8500+ rpm
(short runners open plenum)
it's the butterfly that changes plenum volume that affects the torque.
of course this all theoretical until it gets on the dyno

 

Is it our intake that gives our SE maximas that loud sound during WOT when the car is stock?

 

I think its everything combined which makes it soo loud (compared to a VQ, VG's can be just as loud too).

 

hmmm, I'll say longer straight (key word) runners are for more top end (Edelbrock Street Tunnel Ram) but I think it also has alot to do with the design. That intake is a no bs, just straight down runners (also like the Victors, and M1 Mopars ), while the Performer intakes aren't like that. I completely forgot about the single vs. dual plane part, but we really dont have that many options with our car

(ohh, I know all about the butterfly too, with the Mopar M1 single plane intakes, if you dont have one (ie, make one) you loose out on alot of low end torque, which makes some truck owners not to happy. I still prefer modified stock intakes on that just because its cheaper

 

No, I also have a 1993 VE.

 

Very nice, you have two of the best Maximas ever made. I am assuming you have a VE 5spd, since you mentioned VI as being the reason you have a loud intake?

Shawn, when are you going to remove those "freeze caps"? hehe I am interested myself.

 

2k3TitaniumSe- I know, I saw you mention it in another thread (in fact aren’t you the 1st owner of the car too?)

Aaron- I guess I will, but I want to get my car put back together first. There are only 2 concerns, 1. If I will be able to plug it again (don’t really want to 'destroy' it), and 2. if I will be able to see around inside of it. I think I'm going to use this really small (nickel sized) mirror with a handle on it to help look around inside of it.

I think we should take bets, I think the auto manifolds are 2 separate runners all the way until that area behind the throttle body. I'm going off of the fact that there are 2 'freeze plugs' on high, one low; and that it appeared that the VI area was machined out (even though it very well may have been casted with a hole, then they just machine it out to specs).

 

I don't get why the autos didn't get the VI?

 

That was kinda MY question, too. But moreso, if I took the intake from a 5sp, why couldn't I get it to work?

Although, after looking at pics of the VI, I can probably see why (big ol' actuator valve on the side of the intake).

 

my guess is to help with the 5spds driveability, more torque = not as easy to stall.
Also it could have something to do with you guys having a torque converter

 

yep look at the vacuum diagrams..

i ripped out the manifold and the solenoid valve and vacuum tank and ecu off the parts car to swap it over to my car

you also need the different ecu since the VI valve is actuated not only by vacuum but electrical also

5spd VI


auto non-VI

 

the solenoid lets vacuum by, the solenoid is turned on by a signal from the ECU.

now the problem with using a VI on a auto is you cant swap ecu's. The VI isnt really activated by RPM but instead by engine load, thats the main problem.

I think it would be worth a shot putting it on anyway then wiring up a rpm switch that opens the VI from idle to midrange.

 

Well, I plan to use an RPM switch one day. Nobody has done this swap YET, but many people have been thinking about it for quite some time.

It seems to be a VERY easy swap too.

 

Well now I need to get my car back together so I can find out some stuff for Aaron

In the mean time, here are some updated pics:




Now heres the thing, I've decided I'm not going to mess with the lower intake at this point. The runners on the lower intake start at ~44mm in diameter, while the runners on the upper intake end at only 42mm in diameter. I also dont want to deal with coolant right now.

I am using a 60 grit sanding drum right now, I have a 120grit, and maybe even a 220 (i cant remember if I have one that high), I would probably just leave it with the 60 grit if I didnt have the 120 (heck, i might just do that). the finish of the 60 grit drum is alot finer than the stock casting.

I've also decided to go mild on the porting (well with the intake runners). I dont want to loose my low end and dont really need to gain an extended top end since I wont be able to afford a ECU for quite a while. I am however going to go alittle wild on the throttle body part

 

http://garage.digitalbeta.net/intake...d/VIported.JPG
http://garage.digitalbeta.net/intake.../VIported2.JPG
http://garage.digitalbeta.net/intake.../VIported3.JPG
http://garage.digitalbeta.net/intake.../VIported4.JPG
http://garage.digitalbeta.net/intake.../VIported5.JPG

Brake cleaner is really awesome at cleaning the intake, and getting the gum/varnish off.

although in some areas it looks like I missed a spot or its un even, but it is. Port matched it to the lower intake. I haven't one the throttle body (and that part of the intake) yet. I'll probably do that tommarrow.

 

You do know the reason why stock manifolds are cast with bumps dont you

 

yes. and I'm taking them all out.

ok, actually I havent done much to it, but thats because I dont really want to mess with the power band, I just want to gain a small improvement everywhere.

 

Might be a bit off subject but Does anyone happen to have a variable intake for sale? I also recently did the auto/manual conversion, but didnt swap the intake manifolds. I swapped the wiring harness so now i have an xtra plug just dangling that connects into the green sensor here: http://s92599732.onlinehome.us/intak...s/photo_4.html Not so much a big deal, its just it caused my check engine light to come on. I ended up selling the converted automatic with the variable so im kind a screwed.

thanx for the pic mrgone.
by the way, how long did it take you to get the manifold off. I might just call the guy i sold the car too. See if we just cant swap it out real quick. Anyone know where to get cheap gaskets. $80 everywhere i called.

 

 

Brian for gaskets (if I didnt have a hookup at Napa I would order threw him). Ok actually if I wasnt going to use my magical gasket sealer I would probably order threw him.

The green connector is for the Variable Intake Solenoid. It's function is to turn an electrical signal into a mechanical movement. When the solenoid recieves power a little plunger inside of it pulls back allowing vacuum to pass threw, therefore activating the Power Valve.

Cant really help out on the forsale, except maybe ask the parts cars in the forsale area?

 

From my understanding, the fuel sticks to the casting bumps on the walls and it really helps the mixture or atomization. That is why porting articles say, the closer you get to the injectors, the less you want to shine things up. So, that's why I shined up the throttle body to a mirror finish, then the upper intake to 80 grit and lower intake to a slightly rougher texture. It's still smoother than stock, but it's a little something to consider when porting.

 

Like others have mentioned, I sat down one day and read the FSM and figured just as much. A bit surprising I thought.

The only thing that I was imagining this VI component being for is to reduce the torque at lower RPM so that it's not so hard on the automatic transmission.

IIRC, the autos aren't really known for toughness when driven hard anyway, and torque converters and transmission clutches are only rated to handle X amount of torque. That's just my theory, because if anything the horsepower robbing nature of an automatic would actually benefit from more power, not less.

 

ok guys I put the 5spd intake back on my car today, I didnt mess with the area around the throttle body, or with the throttle body itself. I figured I can always do that later and I wanted to see the difference the porting made.

Man its amazing, I think I gained alittle lowend, I didn't loose any. The main thing is on dry pavement, at about 3000rpm If I go WOT, the tires spin and the needle goes straight to redline (I can also feather the gas for a bit until the cars speed matches the tires speed). Anyway before you could feel it wanting to slip and sometimes it would, but this is sooo much more than I expected.

I am really impressed with how it turned out. I haven't been able to really test it out much because its pretty Icey out

 

Well, icey conditions is the reason for your traction loss. But porting should make you lose low end definitely. Also, a cold VE will make you think you gained a crap load of low end power. My results were, loss of low end and gain of top end.

 

I made sure I was on dry Pavement, I used 3 different areas, made sure first and everything. I wish it was 70* out so I could tell then too.

 

Spinning Kmart brand tires don't count Shawn.

 

The truth hurts Jeffy

 

Yeah. Also, cold pavement and cold tires make for VERY slick conditions. Also, a cold VE is VERY torquey. Let us know when you have more time to test with a warm VE. Also, what did you do? Just port like you showed in the pics?

 

yeah, the last set of pics are all I did.
I figured I can always take off more, but its not so easy to put it back

I didnt do the throttle body so I could feel just the gains for this. It feels like it has more pull in second gear, the mid/upper end just feels alot smoother.


ohhhh! And I had the VTC's grounded!

 

About time you did that.

 

As far as I can tell, my car is an auto and it has the power valve. Am I missing something here?

 

its not a VE