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Bov Recently Installed

PIOTREK

By PIOTREK,
in Engines & Forced Induction

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**RB2530** Proficient

**RB2530**

Posted
Posted

Ok here is a theory I have has for years now but never done the work to prove it...It is just my educated opinion and maybe the other mechanical engineers on the forums may like to comment as well...Anyone else feel free but if you are a non-believer tell me WHY?

My theory is that a plumb back BOV will be slightly better at maintaining turbine spool then an atmo BOV. ie on a gear change the reduction in turbine rpm will be lower with PB BOV than if it was a vent to atmosphere...

The reason is that with a the PB BOV, air is fed back into the intake pipework or inlet of the compressor.

If you look at just the compressor. It is a pump that draws air in and pumps it out. That amount of work the comp does is proportional to the pressure increase across it minus losses. On a gear change the energy input to the comp is close to zero (turbine suddenly is not getting exhuast flow to turn it). So it obviously it slows down. Inertia of the shaft and wheels is what keeps it moving. Without a BOV it slows very quickly because the pressure increase becomes very high. Ok but with any BOV this pressure spike doesn't happen so it won't slow as quickly.

BUT

Another factor that comes into play is the work the compressor does to draw air in through the air filter and the intake pipe work between the afm and the comp inlet. Normally this region is at a slightly negative pressure depending on how restrictive the air cleaner and intake pipework is...

So some of the work of the compressor is expended in just pulling the air through the intake. With a PB BOV though, extra air is introduced into the intake side of the compressor, which on a gear change will overcome this loss. ie for a short period of time, a positive pressure will result in the intake because you are dumping air into this (semi confined due to air cleaner) region. In other words the air exiting the BOV will expand in the intake pipe work will act to keep the compresser sopinning at a higher rpm simply because you are eliminating the losses in the intake.

With an atmo BOV, the energy put into the air post-compressor is just expelled into the atmosphere, never to be seen again...Not to mention the poor ECU that desperately adds fuel for air that it doesn't realise, no longer exists...

If you understand this so far you may be thinking, well the PB BOV will not be as efficient at reducing the compressor outlet pressure because it is dumping into a semi closed region (depending air cleaner etc) instead the atmosphere. I am not sure either, but when you look at the typical atmo BOV, they don't exactly have free flowing discharge...especially the rice ones I've seen..otherwise you wouldn't get pphhhttsshhhh!

PIOTREK Proficient

PIOTREK

Posted
  • Author
Posted
It is fine for your turbo!! It is not going to blow up!! Don't worry about it.

Mate, its fun when you are 16 stututututu, but as we grow up i don't its the best noise for a car to make. I should've bought a VL for that :)

Thanks RB for the detailed explanation, i shows u no your sh&t

PIOTREK Proficient

PIOTREK

Posted
  • Author
Posted

ok conclusion is reached, the flodder has nothing to do with the bov accept that the plump back pipe is causing it. I have adjusted the tention in the spring and all the flodder is coming through the pod. So really the only way to stop the flodder is putting the stock bov back on??

(most poeple would like i'm crazy trying to make a skyline to stop the flodder haha)

Bliksem Veteran

Bliksem

Posted
Posted (edited)

Just put the stock one back on, you dont want an atmo bov when running an AFM.... your venting metered air that the ECU has already adjusted the mixture for, it will run rich and only cause you problems. And its Flutter not "flodder" or "flooder"

Edited by MintR33
PM-R33 Grand Master

PM-R33

Posted
Posted (edited)
Mate, its fun when you are 16 stututututu, but as we grow up i don't its the best noise for a car to make. I should've bought a VL for that :thumbsup:

Thanks RB for the detailed explanation, i shows u no your sh&t

a) I aint 16.

b) I was trying to help you.

c) It's "flutter", not flodder.

d) I didnt say anything about the noise being cool, uncool, i said get over it, it aint doing any damage to your $200 turbo.

e) Im doing mechanical engineering at uni, so pretty sure i understand fluid dynamics a bit better than you.

So thanks for your stupid comment to me, please continue debating your grand modification of installing a BOV.

Edited by PM-R33
PIOTREK Proficient

PIOTREK

Posted
  • Author
Posted
a) I aint 16.

b) I was trying to help you.

c) It's "flutter", not flodder.

d) I didnt say anything about the noise being cool, uncool, i said get over it, it aint doing any damage to your $200 turbo.

e) Im doing mechanical engineering at uni, so pretty sure i understand fluid dynamics a bit better than you.

So thanks for your stupid comment to me, please continue debating your grand modification of installing a BOV.

I think that you need to lighten up, and laugh. No one is attacking personally

89CAL Grand Master

89CAL

Posted
Posted

I know a couple of people that were running atmo bov's and getting flutter at lower boost levels. ie half throttle when boost was only half built. on full boost they usually just vented normally.

A bit of flutter at low rpm ive always seen as ok, when u start running 10+psi with no bov on stock turbo or something like that then yeh its probably not good.

personally... im not all that into atmo bov's. last time i had one on my car my fuel economy halved and it idled like a bitch. I think it comes more down to the bov u put on it though, i had a turbosmart one on there that my car ran fine with and then i had a blitz on there that made my idle hunt really bad.

use the stock BOV or a good blumback. Personally im looking at getting the turbosmart skyline dual port one day. thought it is a bit expensive

  • 4 weeks later...
C.Hawk Contributor

C.Hawk

Posted
Posted

Hi guys need some stuff cleared up.....

1. just bort a r34 gt-t everything is stock ie. ECU AFM ect... so im not sure if the the ATMO BOV that i am running is ok for this car it get a surge sound when below 3000rpm but a very nice WOOSHH when above that....??? is this bad for my turbo or engine?? i herd alot about the stock ecu not copeing well with ATMO BOV's.. btw its a drift vee port bov with hard or soft settings. also i have a pod filter not sure if that matters.

any info would be a great help..

thanks

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