Question About My Skyline..

[08yannch]

An atmo BOV could be muffled. That isn't a great analogy.

atmo BOV is illegal because of sound and emission controls and because there gay

[Ehgriez]

on the note of flutter and damage.

Ive been running my stock turbo with flutter, on over 14psi for a couple months with no issues, taken to drifts and all.

[johnnnnnyboi]

kay well been talkin to a few mates and ive come to the conclusion that ill probs have to get a stock r33 bov as the guy that sold it to me didnt give me any original parts. the turbo already makes heaps of seperate flutter so i dont see why i shud keep my atmo bov that just makes a second noise to it.. anyone that could hook me up with a stock one? cheers.

[Hanaldo]

I assume the stock BoV is just a basic plumb back system? Never seen a stock BoV in a Skyline, don't own a turbo But if the stock BoV has been replaced with an atmo one, wouldn't you need to get another crossover pipe and all that?

[Nic_A31]

How can it flutter AND be atmospheric?

Only way I can think of is its a very small blow off valve, or blocked up a bit.

Stock is pretty basic, yeah.

Blow off valve sits on the crossover pipe, a few inches before the throttle body, takes air from behind the throttle body, and recirculates back to the induction pipe, a few inches before the turbo.

Depends how the current BoV is setup, could be an adapter plate sitting in place of the stockie, or they could have sealed/blocked the stock one, and placed the new one elsewhere on intercooler pipes.

[Tony de Wonderful]

How can it flutter AND be atmospheric?

Only way I can think of is its a very small blow off valve, or blocked up a bit.

Stock is pretty basic, yeah.

Blow off valve sits on the crossover pipe, a few inches before the throttle body, takes air from behind the throttle body, and recirculates back to the induction pipe, a few inches before the turbo.

Depends how the current BoV is setup, could be an adapter plate sitting in place of the stockie, or they could have sealed/blocked the stock one, and placed the new one elsewhere on intercooler pipes.

You could put the BOV before the intercooler that way you are not venting your cool air way.

The stock plumb back BOV...I mean the air that is circulated back to just before the turbo, where does it go exactly? Some of the charge must go back through the AFM and out of the air filter?

[Nic_A31]

No, it recirculates after the air flow metre but before the turbo. Between the turbo and the vacuum the air will just repass through the turbo, and keep going until it reaches the blow off valve and recirculates again.

It needs to be after the AFM for the same reasons as atmospheric BoVs. If the AFM counts the same air twice (or not at all), after each actuation, you will have a split second of running rich / lean (this is why you get rough idle / engine stalling with atmospheric blow off valves). This is why they're illegal - emissions.

EDIT: Above effect applies to upstream air flow meters only. ECUs that use MAP sensors and monitor air in the intake manifold won't suffer this effect.

Edited January 17, 2010 by Nic_A31

[Tony de Wonderful]

No, it recirculates after the air flow metre but before the turbo. Between the turbo and the vacuum the air will just repass through the turbo, and keep going until it reaches the blow off valve and recirculates again.

It needs to be after the AFM for the same reasons as atmospheric BoVs. If the AFM counts the same air twice (or not at all), after each actuation, you will have a split second of running rich / lean (this is why you get rough idle / engine stalling with atmospheric blow off valves). This is why they're illegal - emissions.

Ok I see so it (the bypass valve) is equalising pressure either side of the turbo then, still I find it hard to believe the system is totally closed. I mean at WOT there is a decent volume of charged air between the turbo and throttle body especially w/ an FMIC. I can't see how if you then equalise the pressure between either side of the turbo you don't end up with more than atmosperic pressure either side and thus some air must flow back out through the AFM (where else can it go?). I know on my car I can get a rich 'pop' from the 'zaust at gear changes at full boost.

[Nic_A31]

No, the idea of a blow off valve is to keep the vacuum in one direction. Surge occurs when the throttle body closes and high pressure air has nowhere to go.

Even if the blow off valve is small, it still keeps vacuum in one direction, and then once the air passes through the blow off valve, it goes through the turbo (again) which is no longer compressing (or compressing as much), so the pressure is released very quickly on both sides of the turbo.

With FMIC, high boost and you've got a responsive intake system, if you drop from full boost/redlining down to idle quick enough, you will get some surge for a split second, depending on where the blow off valve is located (the further away from the throttle body, the more likely) and how long the blow off valve takes to open.

[FEARNOV8]

johnnnnnyboi u rather get advice from a performance shop with mechanics who have been in da game for a while then u will know for sure u getting the rite advice( but hey dats my oppinion)..yea and kaido is rite if u have a stock ecu u get alot of backfire with an atmo bov thats wat happens with mine but once i get a afc and get it tuned it will be all gud ..quick question guys, can a stock bov handle 200kw?

Edited January 17, 2010 by FEARNOV8

[Nic_A31]

Ask a performance shop mate - they'll know

[D_C]

you can get a stock bov from a wrecker like KYP www.kyp.com.au they got a shop in welshpool

[FEARNOV8]

lol but u sound like u know wat u talkin about nic_A31 but yea its probably best.. i was told at my job from one of the mechanics dat a stock bov on a rex can handle 300hp so yea just thought a rb25 one can handle da same

[Nic_A31]

Aftermarket BoVs are useless and serve simply as a decoration, they'd do not increase performance (even if they were featured in The Fast and The Furious), and you do not need to upgrade them if you're going over 300hp or adding stickers...you don't need to change them at all. The stock ones work perfectly fine, and they're about as quiet and emissions friendly as you'll get...removing them in favor of some loud A/M atmospheric one is retarded.

[FEARNOV8]

yea and i get so much backfire..but if i was going for high hp numbers then ill prob need a aftermarket plumb back bov but yea for now 200kw will be fast enough haha..are u a mechanic?

[Dani Boi]

you know the reason the car runs like shit has nothing to do with the bov itself, its due to poor install and the stock ecu.

Also you will only be able to run one gtr bov unless you want to spend $$$ mod the twin setup to work correctly.

just get yourself a stock one, i have laying around you can have

If your getting a tune with a pfc/safc then by all means have the atmo bov on, but your still going to be gay nonetheless, down $200+ for no performance improvement and a free yellow to go with it...

And gts't's work fine with one gtr bov...

Edited January 18, 2010 by Dani Boi

[bubba]

How can it flutter AND be atmospheric?

Only way I can think of is its a very small blow off valve, or blocked up a bit.

The ARC I had on my 30 fluttered and it was atmospheric venting.

I had to tighten it up so much because it was being forced open at idle that it would only vent fully with a full-boost quick lift off.

[Hanaldo]

yea and i get so much backfire..but if i was going for high hp numbers then ill prob need a aftermarket plumb back bov but yea for now 200kw will be fast enough haha..are u a mechanic?

It really doesn't matter how much power you are making. The point of a BOV is to compliment the turbo, they release the pressure so that the air doesn't get forced back through the turbo, slowing the rotational velocity of the compressor wheel which means the turbo will take longer to spool up (and also potentially causing damage to the turbo). A BOV is just a valve, with the only purpose being to release charged air. There is no performance gain from an aftermarket BOV compared to the factory one.

The only reason to change the BOV would be if you were running very high boost and the valve wasn't letting all of the charged air escape

[Curtis.Cow]

you tell them martin, haha... i should be gettting my bov in the mail soon woot going to see how it works

[johnnnnnyboi]

cheers for a little more advice i guess i will go to a performance place for some advice to answer some of your questions it dosent have a stock ECU unit its had a new monza fitted one... i duno how good that brand is... and yeh i do get a bit of backfire sometimes and the car has stalled occasionally when ive been driving it but not really often just rarely. the boost is run really really high... on my boost gauge it usually is at 15 sometimes.. 20... i duno this is all just figures to me.. i think the fuel lines have been pressured to release maximum? this is just a few things coming from my home mechanic. duno if its right?