Altima 3.5L V6 butterfly valve removal (write up & discussion)

[SlateSER1788]

I've looked around on google and here to find a butterfly valve removal write-up and I couldn't find one so I decided to make one myself. The whole process should take around 30min to do, a lot shorter time than it took me to do it on my '02 Sentra SER Spec-V (QR25DE). Since the SER (Altima) has a V6 in it, the VQ35DE engine's intake manifold is a little different, but in a good way.

But first I'll start off by explaining what the "butterfly valve" is and what the whole deal with it is.

What's the butterfly valve?I had a 2002 Nissan Sentra SER Spec-V before I bought my Altima SER and after lurking the forums I realized that not only did my car have a ticking time bomb in it but so did every other 4-cylinder (QR25DE engine)Sentra/Altima out there... and apparently so do the V6 (VQ35DE engine) Altimas/Maximas, due to these so-called "butterfly valves".

The issue is with the intake manifold. If you look at the QR25DE engine's intake, right where the throttle body connects to the intake manifold there are 2 "tunnels" that start to lead into the engine. Tunnel #1 (your "primaries") leads directly to your engine and when you throttle the engine, air intake flow goes right into the engine. On tunnel #2 (your "secondaries") halfway down it is blocked off by metal plates, and each plate has 2 screws in the middle of it that secure the plate to a rod that turns. These plates stay horizontal ("closed", restricting airflow so that air only passes through your "primaries") up until about 5,500RPMs or so. Once your RPMs hit the 5,500RPM (or so) mark, a vacuum line controlled by an actuator (I believe...?) makes the rod turn on your "secondaries", making those metal plates go from horizontal to vertical, allowing much more airflow to come into the engine because now air is being directed through your primaries AND secondaries. This is why you'll hear a loud "roar" erupt from your engine if you have an intake installed when you hit that 5,500RPM mark because the noise is the result of your secondaries opening up.

The V6 (VQ35DE) engine is similar but it doesn't have 4 butterfly valves like the 4-cylinder does, the V6 just has one decent sized one. The problem is, some cars left the factory without having loc-tite put on the screws that hold the plates (butterfly valves) onto the rod. The result is that the screws and sometimes even the plates work their way free and get sucked into the engine. If that happens your engine is pretty much done for...

I'm not sure if Nissan has released an official recall for this issue but I'm sure if you mention it to them they will do the work to address the issue.

Why remove the butterfly valve(s)?You don't have to remove the butterfly valve(s) if you don't want to. On my Sentra SER Spec-V that I had I just loc-tited the screws myself and left the butterfly valves installed.

Some people remove the plate(s) and screws so that they don't have to worry about them getting sucked into the engine, PERIOD. But on top of this, apparently you can gain some mid-range to top-end horsepower by not having the valve(s) installed, but you will lose low-end torque.

I removed the butterfly valve on my Altima SER (V6) because (A) I didn't know if the screws had loc-tite on them (which they did, thank god), and (B) I wanted to see what the difference was. I honestly didn't noticed much of a difference (low, mid, or top-end) but I did notice that when I went under medium to heavy acceleration that my short-ram intake/engine was a little louder, which I like. Something to look into as well (which I found after I removed my butterfly valve) is the NWP Engineering VIAS/SSIM Block Plate shown in the link below:http://forums.maxima.org/group....html

The link above also has a good explanation on what some terms are like "VIAS" (Variable Induction Air-control System), which is what Nissan refers to their intake and intake manifold system as.

Here is just one story of what can happen if your butterfly valve screws become loose: http://www.nissanclub.com/foru....html

And here is a link to how many 2.5L QR25DE engines had loose screws, missing screws, etc.: http://www.b15sentra.net/forum...erfly

I know that I am providing links and examples of issues with the 2.5L QR25DE engine and not the 3.5L VQ35DE engine, but the 3.5L uses the same 2 screws and butterfly plate that the 2.5L does.

Instructions on Removing the Butterfly Valve**IF YOU HAVE THE 2.5L QR25DE MOTOR, GO TO THIS LINK: http://www.nissanclub.com/foru...=1448 FOR INSTRUCTIONS ON REMOVING YOUR BUTTERFLY VALVES**

**I'm not doing this write up while I'm doing the butterfly removal process, I already removed it and am going off of memory so please let me know if I messed up on anything**

Tools Needed-Socket set (will provide exact sizes soon)-Needle nose pliers-Phillips screwdriver (drill might be needed)-Allen wrench (will provide exact size soon) if you have your plastic engine cover still on

Optional-Throttle body cleaner-Rag(s)

Procedure1. Let your engine cool... This might be obvious to most people but make sure your engine isn't hot.

2. Disconnect the negative terminal on your battery. I did this mainly for safety purposes but also to reset my car's computer (if that's possible...), I read somewhere that this was good to do if you're installing an intake so that when you do start your car back up it can recalculate intake readings, flow, etc. but I don't know how valid that is... but I did it anyways.

3. Remove your plastic engine cover by loosening the 4 allen bolts in the top of the cover, if you have it installed.

4. (A)Remove the bolt holding the wire bundle to the engine, (B)loosen the wire bundle "zip tie pins", and (C) remove the VIAS (Variable Induction Air Control System) bolts:

(A and C)

(B) There are about 3 or 4 of these "zip tie pins" (as I call them) that secure the wire bundle to the engine. Use a pair of needle nose pliers to compress the pins and then use your other hand to pull the zip tie assembly out of the bracket. You need to do this in order to get to the bottom rear VIAS bolt in step "C".

5. Once you have the VIAS bolts undone, you should be able to pull out the whole butterfly valve assembly. It's a tight squeeze trying to get it out and over that black wire bundle but you should be able to get it out.

6. Once the butterfly valve assembly is out, remove the two screws on the butterfly plate. You will need to hold the valve in the "closed" position (straight up and down) to be able to unscrew the screws. I was surprised, but mine actually had lock-tite on the screws, my Sentra SER Spec-V did not... Be careful not to strip the screws too. I had to use my Dewalt drill with a wide and fat phillips head on the end of it to get one of them out because I almost stripped it...

7. Once the plate is removed I suggest that you wipe down the butterfly valve assembly to remove any dirt, lock-tite, or oil that might be on it. Also, I sprayed a little bit of the cleaner on the inside of the intake manifold and wiped down the inside of it the best I could since I had access to it. Shown below is where I found oil and dirt on/in the intake manifold:

8. Now that you have removed the butterfly valve and cleaned everything, put the butterfly valve assembly back into the intake manifold, insert the 3 bolts and tighten (don't forget the gasket!!(thin, black metal piece that is in between the manifold and the butterfly valve assembly)).

9. Pop the zip tie pins back into their holes and screw in the bolt from step 4 (A).

10. Re-install your engine cover and screw in the 4 allen bolts, and re-connect your neg. terminal on your battery.
Modified by SlateSER1788 at 9:05 PM 11/22/2009

[dldjros69]

i could use google but would rather have it explained to me.

What the heck is the butterfly valve and what does it do?

What is the point of this write up? What are you trying to achieve?

[SlateSER1788]

i could use google but would rather have it explained to me.

What the heck is the butterfly valve and what does it do?

What is the point of this write up? What are you trying to achieve?

I will explain this in my post when I finish the write up, I'm actually still working on it now

UPDATE: write-up is finished, comments/questions are more than welcome.
Modified by SlateSER1788 at 4:42 PM 6/7/2009

[Nlghtmare]

This is all very interesting but why are they there in the first place?Is there something I don't understand.

Also, are there any cons to removing the valves besides the loss of low end torque?Is the horsepower gain worth the loss of torque?

[FGFCacoupe]

Thanks for the write up

[mcheddadi]

Oh, and btw, CUSTOM TITLE GET! ask a mod for one

[blackteam02]

S000oooOOoo0. . . what about the 3.5?

hey mcheddadi, is this a go for us 3.5ers? im kinda skuRRed to try this with the injen intake on.

[SlateSER1788]

S000oooOOoo0. . . what about the 3.5?

hey mcheddadi, is this a go for us 3.5ers? im kinda skuRRed to try this with the injen intake on.

This is a write-up specifically for the 3.5, I just mentioned the 2.5 in the beginning to give you guys a little background on the issue (for those that haven't heard of the butterfly screw "ingestion" issue).

And I have an Injen intake on my car and everything has been fine, I'm actually very satified with the results.

[SlateSER1788]

This is all very interesting but why are they there in the first place?Is there something I don't understand.

Also, are there any cons to removing the valves besides the loss of low end torque?Is the horsepower gain worth the loss of torque?

From what I've read, they're there to:

A) Help with exhaust emissionsB) Help maintain l0w-end torque and open up at higher RPMs to allow more airflow resulting in increased power

Granted, I am not quoting any particular site or anything by Nissan with the information above, I am merely summarizing numerous posts/articles that I have read online.

[SlateSER1788]

Oh, and btw, CUSTOM TITLE GET! ask a mod for one

Custom title? I'm assuming you're talking about something like the phrase "Photoshop God" that shows up under your name?

[blackteam02]

so what exactly did YOU "gain/lose" give us a day in the life of having no butterfly valves. . im wondering because i do alot of driving, i lose gas mileage right?

[rich2342]

Is this like the VIAS /nwp block plate mod for the 3rd gen or is the butterfly valve different.

Aren't the setups on the 4th gen different?

[Dexion]

Yes the 4th gen's are different we actually have two of those suckers! So far I do not see a reason for removal on the 4th gen VQ's

[mcheddadi]

yep! email brian about it, he'll give you one http://forums.altimas.org/zero...74179

[SlateSER1788]

Yes the 4th gen's are different we actually have two of those suckers! So far I do not see a reason for removal on the 4th gen VQ's

Haven't checked this thread in a while...

I'm not sure what the effects would be on the 4th gen, I've only done this on my SER. I did it because I was curious as to what would happen and now that it's 5 months later I can honestly say I haven't experienced anything bad as a result of doing the mod.

My intake got louder, gas mileage went down maybe 1-2mpg when I really get on it (but can still achieve 26-28mpg on the highway with current setup in my signature, roof rack consumes about 2-3mpg) and I loss a *little* low-end torque but it seems to have better flow in the higher RPMs.

Once I get my OBX headers I want to do a few more tweaks (BullyDog ECU flash) I'm going for a Dyno run and will post results, but this might not be until Spring time or so.

[Dexion]

With the 4th gen's everything past the throttlebody until the heads is made of plastic. And just by looking I can tell we have two VIAS points in the intake manifold.

I just took a quick look, we have one side which looks identical to the VIAS point of the 3rd gen. Its on the right side of our manifold right next to the TB. The other one is HUGE and is on the left side of the manifold (where the 3rd gen VQ one is) I didn't open them up because they are both connected to wires which lead into the engine.

[Stumpjumper]

I don't know if the same applies to the Nissan, but removing the butterflies in my old duratec that was in my 2000 cougar was dyno proven to lose some low end torque for no real higher rpm gain. Again, not sure if the same would apply to the Nissan VQ or not.

[rich2342]

With the 4th gen's everything past the throttlebody until the heads is made of plastic. And just by looking I can tell we have two VIAS points in the intake manifold.

I just took a quick look, we have one side which looks identical to the VIAS point of the 3rd gen. Its on the right side of our manifold right next to the TB. The other one is HUGE and is on the left side of the manifold (where the 3rd gen VQ one is) I didn't open them up because they are both connected to wires which lead into the engine.

Granted we have the new Plastic which eliminates turbulance can a spacer be added? Would it be of benefit?

[SlateSER1788]

The other one is HUGE and is on the left side of the manifold (where the 3rd gen VQ one is) I didn't open them up because they are both connected to wires which lead into the engine.

If there's wires connected to it then that makes me think that some type of sensor is in there and I personally would just leave it the way it is. With my SER there is just a vacuum line that runs there to operate the valve.

[Dexion]

Nah I think spacers won't do much of anything, not worth the cost.

[SlateSER1788]

Nah I think spacers won't do much of anything, not worth the cost.

I agree. If you're going to get something "minimal" like this, I would get a used one off of someone on the forums here if you can find a seller.

I did a quick search and found one by "HorsePowerFreaks" (manufacturer) for $100... I'm sure you could get one for less but if you're going to spend that much money on something like a "spacer" I would much rather spend it on a light-weight pulley (like Unorthodox Racing) for around $190, a short-ram intake (price varies), etc. to get more "bang" for your $$$.