Ever since I did my TT conversion I was having a problem with the car stalling out, mostly during throttle transitions. I found the cause of the problem and solved it this evening.

I have a greddy type-RS clone BOV, which has 1 "vacuum assist" nipple on it that was coming off a "T" fitting in the vacuum line for the FPR. I would hear a "whistle" when I would come off the throttle. It turns out the BOV was opening up and SUCKING IN air. This would cause my AFR to jump WAY lean (20-21) and the ECU would fire the injector to make up for it. Guess what, the car would die right after that. I would then restart the car and the AFR would be WAY rich (6-7) for a few seconds, then the AFR would even back out again to normal. I removed the vacuum line from the BOV but even on the lightest spring setting, it would not open, and I didn't want to kill my turbos with compressor surge. So, I pulled an Adam on my BOV and took it apart.

Inside the top housing is a "double spring" (one spring inside the other) and a few spring retainers. I removed the "outter" spring and put it all back together. Guess what, I no longer need to hook up the "vacuum assist" nipple, and the BOV works great now.

I am sure the BOV was designed for higher boost then what I am running right now, so that is why it has two springs, but it is cool to know that it has the ability to be used for my low boost setup with just a simple modification.

_________________
1993 3000GT VR-4 (build in progress)
1994 3000GT SL
Lead, Follow, or get out of my way!

Also know as:
"dead weight", "wrong wheel drive noob"

For crying out loud John, I'll GIVE you a stock BOV to install if that POS is all you're stuck with.

The vac nipple is supposed to be hooked up in order to pull the piston open when the throttle plate closes. Now, you're simply relying on boost pressure to push it open. This is not good and there's a number of reasons why.

The main one being the delay it takes for the BOV to open. While at 5psi, it may not create enough surge for you to hear, but I can guarrenty it's still there.

I have no idea what pressure that spring is rated at, but I'm guessing once you start running more boost, it'll force the piston open when you're accellerating = boost leak = overspinning the turbos.

_________________
06 Blue EVO 9

Yes, I might believe that taking out a spring helpped you out. BUT, like greg said, that nipple is important.

It helps to activate the BOV when you shift.

right now your depending on the "pressure surge" when the throttle body slaps shut. which also could mean that the same pressure could possibly get to the compressor of the turbo.

I just checked up by my fathers house this weekend.

I have the stock BOV that came off my car. Also, like Greg, no charge. you just have to come get it.

It does leak. (just like it was designed to.)

I also have a type-S (with the nipple capped) that you can try for a while, but I will want it back eventually.

I'm not sure what the deal is. definetly bring that thing to the GB gathering, I want to take it apart and see the difference. (I assumed there wasn't much between the type S and the RS...)

Adam

EDIT:
Also, where and how do you figure it was pulling air in from? 'splian it to me.

_________________
Bad decisions make good stories.
Look at it! LOOK AT MY @SS AND TELL ME IT'S PRETTY!

Ok, here is what I did. I moved my boost gauge over to the "T" fitting that I was using in the FPR, to see how that was working (vacuum, boost) and I found that the vacuum line to the FPR never sees boost, the highest I saw it go on the boost gauge was 0. When I would shift, or come off throttle it would jump down to vacuum again, and that would pull the BOV open and suck air IN through the BOV and into the vacuum line.

_________________
1993 3000GT VR-4 (build in progress)
1994 3000GT SL
Lead, Follow, or get out of my way!

Also know as:
"dead weight", "wrong wheel drive noob"

I'll bring my stock BOV Wed. so you don't have to deal with it.

_________________
'94 vr4- Now with extra slowness

um. ok.

first, not seeing boost in the FPR line seems wrong to me. which nipple is it hooked to? Are you seeing boost when you put the gauge to the back of the plenum? have we pressure tested your car yet?

second. It should go into vacuum when you let off the throttle, or shift gears. that's normal. That vacuum is what should be pulling open the BOV.

What is not "normal" is that it "leaks by the BOV." I mean, air should go from the Y-pipe to the splitter. that's the BOV's function. (only in your case it goes to atmosphere.) It should not leak into that nipple, which is what I think your saying. but I have no idea what is inside that BOV. Is there a "rubber membrane" that can crack, or what?

Adam

_________________
Bad decisions make good stories.
Look at it! LOOK AT MY @SS AND TELL ME IT'S PRETTY!

Adam, I think the pre-OBD2 DOHC NA "P ports" on the throttle body are different from the turbos in that they are a sourced before the butterfly valve unlike the turbos which are after which is why he wouldn't see vac on the gauge when tapped there.

He has the FPR vac sourced in the correct spot (nipple just after the TB)

edit: I examined an NA TB and don't see any reason why boost should not be comming out the P port as it's sourced after the butterfly valve.

Yes, I realize that, but I need to find a way to not have the car stall out. If I remember right, if I tighted the spring more and left it hooked up to vacuum, the BOV wouldn't open at all.


The only "rubber membrane" I found was on the valve body it's self, but that just sealed the top chamber from the bottom chamber. Once the valve is open, there is nothing between the lower chamber and the "vacuum nipple" that I can see.

_________________
1993 3000GT VR-4 (build in progress)
1994 3000GT SL
Lead, Follow, or get out of my way!

Also know as:
"dead weight", "wrong wheel drive noob"

But Greg, what I'm reading (unless I'm miss reading.) is that he can't see PRESSURE there. His FPR is not seeing any boost, which should close the regulator to raise fuel pressure. (at least on the turbos, on the NAs, meh, I don't really know,) but, regaurdless what it "should" do, he definately should see pressure there, it's just a dumb nipple.

Unless he's not making enough exhuast heat to spool the turbos, or no load, (like from a slipping clutch), or a massive f***ing boost leak.

I dunno, seems like something is missing here. which is why I asked if he saw boost when the gauge was hooked up before...

Adam

_________________
Bad decisions make good stories.
Look at it! LOOK AT MY @SS AND TELL ME IT'S PRETTY!

Yes, I see boost on the y-pipe, and yes, I have presurre tested my car. 18.5 lbs at unclebenny's place.

_________________
1993 3000GT VR-4 (build in progress)
1994 3000GT SL
Lead, Follow, or get out of my way!

Also know as:
"dead weight", "wrong wheel drive noob"

Ah, now that I reread that, I see.

Well, when I was out there, he had it hooked up to the stock spot (which should be correct). If there's no boost comming thru that nipple, there's something else going on as there's no interferience with that nipple.

but no vacuum...?

And, if you move the gauge to the back of the plenum, then do you still see boost? that should be reading from the same place as the "FPR." Should be...

_________________
Bad decisions make good stories.
Look at it! LOOK AT MY @SS AND TELL ME IT'S PRETTY!

I see just a little vacuum on the y-pipe, maybe 1-2 cm/hg, but that is about it.


The only places I have moved the gauge to on the plenum is the "p port" and the "t" fitting on the vacuum line to the FPR. both of those only show me vacuum. Those are the only places I can find the hook up too.

_________________
1993 3000GT VR-4 (build in progress)
1994 3000GT SL
Lead, Follow, or get out of my way!

Also know as:
"dead weight", "wrong wheel drive noob"

how much boost do you see at the back of the y-pipe, and when...?

_________________
Bad decisions make good stories.
Look at it! LOOK AT MY @SS AND TELL ME IT'S PRETTY!

Think about it Adam, there wouldn't be vac at the y-pipe. The reason motors create vac is because the pistons suck the air in and the throttle body makes a restriction. There's no vac at the y-pipe because it's before the throttle body.

On an NA plenum, there's only 1 small nipple to source. It's in the same spot where the BOV is sourced at in a turbo plenum. The only other vac/boost source is the P port on the TB.

John, your either your car isn't making boost, there's an issue with your gauge, or you're just not seeing it (it's in a bad spot to see while driving). When I looked over your vac routing, it was all correct.