Welcome to the North American Subaru Impreza Owners Club Sunday July 13, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC General > Newbies & FAQs

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 09-22-2008, 01:08 PM   #1
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default BOV FAQ: The REAL dirt on BOVs. Ups AND downs. Lets dispell some myths.

OK!

Based on the recent influx of BOV related posts, and the ensuing garbage that many people have posted in reply to these, I have decided to make up a small FAQ to try to squash some of the rumors and just straight up bad information out there.

Yes, Unabomber has an FAQ on this. The fact is that it doesnt "get to the point" fast enough for most people to get the point. This is written more bluntly, addressing some issues head on.
We dont need 329872389472387 bits of data and links to valves. We need misconceptions fixed, and we need people to stop repeating the same bad info over and over. Or at least hopefully slow it down a little bit

First, some vocab, since some dont know what it all means

VTA=Vent to atmosphere
-this is the noisey style that is the most popular. 90% of BOVs out there are fully VTA (meaning they vent 100% into the air)
Recirc
A BOV that dumps the vent back into the intake stream. Before the turbo, after the MAF sensor.
50/50
Vents half into the intake, half to atmosphere. Makes some noise, doesnt swing as rich. Typically these are set up sequentially, so that on light vents, it dumps 100% back into the intake, this is so that at light boost/part throttle you get no rich condition, and no/less noise. At higher boost, the valve opens all the way, and dumps into the intake and atmosphere.

Now lets clear a couple things up. If it seems like I am pro-bov, just read everything. I get to the down sides further down.

1. BOVS make you run rich.
--No they do NOT! Here is why. When you are idling, driving around, and under boost, the BOV is CLOSED just like stock. The only way to be running rich is if the BOV was somehow letting air out post maf, WHILE RUNNING, constantly. The exception to this would be a valve that is leaking REALLY badly, and in a case like this, you will know there is a problem right away anyway, as the car will probably barely run. For it to leak this badly, it would have to be physically damaged or just REALLY f'd up


2. But what about when you shift? Arent you rich then?
--Yes. BUT, you need to understand a couple things.
First-The rich condition is not THAT rich. On most tunes the target A/F under boost is @11.1-1 or so. Say you are at 11.1-1, then you shift and it vents. It will swing rich, typically to around 9.5-1. That is NOT that rich.

Second- The rich condition does not last very long. On a typical datalogger, the rich condition takes up no more than 2 rows. You are rich for well under a second.

3. I heard its bad for my cats!
--Its not great for them, but its not really enough to shorten their lifespan in any meaningful way. Exactly how long are you planning to keep the stock cats or even keep the car anyway? Seriously, there are guys running around with 100k+ on their car, totally stock exh, with a bov. No cat problems. If you have a VTA blow off valve, and you lose a cat, you would have lost it anyway, because either the cat was bad to begin with, or your vehicle has some other issue

4. But people will think I am a ricer!
--Did they pay for your car? Are they making your loan payments? Will them thinking this stop you from getting laid? Exactly, then tell them to die in a fire and enjoy your BOV if that is what you want.
It should be noted however, that if you are the type of person that doesnt like people trying to race them, you may want to stay away from a BOV simply because so many ricers think that everyone with a BOV wants to race.

5. I heard that if I want one, I should do a 50/50 venting BOV.
--These are somewhat pointless. You still get the rich condition, just not quite as badly. However, it isnt that bad anyway to begin with. These are however good for people that want a little noise when they are on it, and little to no noise when they arent on it hard. Dont fool yourself into thinking that you wont run rich (because you wont "run rich" with a fully VTA valve either), you still dump post MAF air when it vents, so you still get a rich spot when it vents.

6. But I need one because I run more boost than stock.
--In most cases this is not true. GENERALLY the stock valve can be trusted till @20PSI. Some leak a little bit after about 18PSI, but 90% hold rock solid till about 22PSI, and 99.99999% hold solid at 20PSI. If you are planning to run more than 24PSI, you may want to consider going aftermarket. Over 26PSI, you need to either mod your BOV, or go aftermarket.

7. So BOVs are fine? I can run one with no real downsides?
--Not always. MOST aftermarket valves leak. A leaking BOV, DOES slow you down, and can over time, damage things. To make matters even worse, 99% of people who buy BOVs, dont know how to, or bother to, take the time to set it up properly. So even if they bought a quality valve, it may be leaking.

8. I have had XXXX brand valve for years, it has never leaked.
--How do you know? By looking at your boost gauge? Looking at the boost levels in your datalog? Niether of those prove that the valve isnt leaking.

9. Ok so how do I set my BOV up, so that it doesnt leak/stands less chance of leaking?
--Read the manual first off. Learn how to adjust it. If it doesnt have a manual, just look at the valve. You can almost aways figure out how to adjust it. Some have screws and such, some use washers under the spring. Others use replacement springs.
Now that you know how to adjust it, here is what you do.
First off, start the car, get out and open the hood. If you can see the piston of the valve (look in the hole it vents out of if its a VTA valve), check to see if it is moving at all at idle, or worse, partially open. You want that piston rock solid not moving at idle.
Now give it a little gas. It shouldnt move when you step on it, and when you lift, it should pull up a bit. Depending how hard you hit the gas, it will either JUST move, or fully open.
If its doing anything but what it should be, adjust it a little tighter.

Now go drive the car

When you shift at light throttle, is it venting? If so, is it a pure straight vent, or do you get a little bit of a "chufchchchc" noise right before it vents? That noise is compressor surge. Which isnt as bad as some people like to think and say. Ideally, you are looking to hear a little surge then a vent. Or no sound at all. Either is ok. Now drive it hard, does it surge a little or just straight vent?
Get out of the car and tighten the valve and drive it again. Repeat this until you get a LOT of surge when you lift under boost. Now start loosening it until you JUST start to hear no almost surge.
What the surge means is that it fought opening just a little bit. If you hear a LITTLE surge just as it begins to vent, that means that the valve is holding itself shut as tightly as it is capable of, without being so tight that it doesnt vent properly.

10. But OMG, compressor surge is horrible for your turbo!!
--Unless its really bad, it really isnt going to kill it. I had a conversation with Corky Bell (Author of MAXIMUM BOOST) during a BBQ at his shop about this exact subject and he assured me that compressor surge was nothing more than a bad sound, and that his early miata turbo kits didnt even use one, and never had problems with losing the turbo. This goes against everything I had previously heard, but as one of the godfathers of turbocharging I am going to take his word for it. This guy knows more about the subject than 90% of nasioc all added together.




Bottom line is this.
If you are wanting to be 100% sure you arent losing any power from it, and you are running under about 22PSI, you are best off sticking with stock. If you REALLY want the sound, then stock with a GOOD valve. You would be suprised at how many big name and very popular valves are junk.

Generally you can trust
TurboXS, APS, Perrin, TIAL (best one out there), the HKS RACE valve (not the SSQV) and a couple others. There is one very popular brand that makes a lot of 50/50 style valves, I am not going to name names, but searching my name and BOVs should bring it up. Its 3 letters and they are known for 50/50 valves.

How do I know this? Like what am I using to base my opinions?
I spent a good long time several years back testing valves. As many as I could get my hands on. Buying, borrowing, trading, you name it. All in all I had easily 30+ valves on my car. Multiple examples of the same valve whenever I could, to help eliminate the chances of getting just an extra bad (or extra good!) valve.
I was shocked at what I found. Almost all leaked.
* Registered users of the site do not see these ads.

Last edited by Davenow; 01-01-2010 at 11:45 PM.
Davenow is offline   Reply With Quote
Old 09-22-2008, 01:08 PM   #2
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default

11. So if I am making the same boost pressure, why does it matter if its leaking a little?
--Because even if you are hitting target boost, your turbo is having to work harder to get there. A harder working turbo produces a hotter air charge, as its higher in its efficiency range (or worse, completely out of it). This means less dense, which will produce less energy when ignited. This also means higher chance of detonation, which even if its very light, will result in your ECU pulling timing. Also bad. Lastly, hotter air in=hotter air out. Higher EGTs. Even if only slightly.

Last edited by Davenow; 09-22-2008 at 01:18 PM.
Davenow is offline   Reply With Quote
Old 09-22-2008, 01:12 PM   #3
AlxSti
Scooby Guru
 
Member#: 94615
Join Date: Aug 2005
Chapter/Region: MAIC
Location: Wilmington, DE
Vehicle:
|'06 STi 341/356|
www.AffinitiBrokerage.com

Default

why do i feel like i've read this exact thread before?
AlxSti is offline   Reply With Quote
Old 09-22-2008, 01:15 PM   #4
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default

Quote:
Originally Posted by AlxSti View Post
why do i feel like i've read this exact thread before?
Because you havent?
Davenow is offline   Reply With Quote
Old 09-22-2008, 01:15 PM   #5
Jubert69
Scooby Specialist
 
Member#: 167739
Join Date: Dec 2007
Chapter/Region: Tri-State
Location: CT
Vehicle:
04 WRX
ej207 spec C

Default

Quote:
Originally Posted by AlxSti View Post
why do i feel like i've read this exact thread before?
same here
*cough unabomber
Jubert69 is offline   Reply With Quote
Old 09-22-2008, 01:21 PM   #6
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default

Quote:
Originally Posted by Jubert69 View Post
same here
*cough unabomber
I made FAQs long before him.

And his FAQs are so out of date, its not even funny. Unfortunately he is just too busy to keep them updated, and as new things are discovered, and things change over the years, they become less and less useful. The other problem is that his FAQs are based on a compliation of posts on nasioc, AND his own knowledge. The unfortunate reality is that much of the stuff in his FAQs, is based on things that were never correct to begin with, because a lot of the threads the info came from, were wrong to begin with.


If his FAQs were working, there wouldnt be nearly the problems that there are. The problem is that his FAQs dont get straight to the point, and dump out a bunch of tech info that many people just dont understand or take the time to bother reading. This FAQ was made for ONE purpose. To get straight to the point, and try to squash some of the myths.


Not to mention that I know more about it the things I write FAQs on. 20 years automotive experience teaches you a few things

Last edited by Davenow; 09-22-2008 at 01:30 PM.
Davenow is offline   Reply With Quote
Old 09-22-2008, 01:59 PM   #7
caracer22
Scooby Specialist
 
Member#: 171076
Join Date: Feb 2008
Chapter/Region: SCIC
Location: Lancaster, CA.
Vehicle:
2011 Wrx DGM
STG 2

Default

Nice FAQ!!! non biased!
caracer22 is online now   Reply With Quote
Old 09-22-2008, 02:01 PM   #8
Super_HKS
Scooby Guru
 
Member#: 154434
Join Date: Jul 2007
Chapter/Region: NWIC
Location: USMC Land
Vehicle:
2009 WRX Hatch <@_@>
SWP

Default

Here are my 2 cents
I love my turboXS RFL.
my car is fully catless and stage 2.
My car holds boost fine
My car idles perfectly
My car's backfires are minimal
The sound is amazing

Thanks for a good post. Hopefully some of the noobs will be able to read it before posting stuff

Last edited by Super_HKS; 09-22-2008 at 02:07 PM.
Super_HKS is offline   Reply With Quote
Old 09-22-2008, 02:03 PM   #9
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default

but how do you KNOW its not leaking?

TurboXS valves in general work very well. Just gotta use the right amount of washers for your particular car.

Oddly enough, the normal type-H seems to work a little better than the RFL. I cant for the life of me see ANY reason whatsoever for this, they are identical other than the horn on the RFL. But the 3 RFLs I tested had to have an additional washer to hold the same as the normal type-H.
Davenow is offline   Reply With Quote
Old 09-22-2008, 02:15 PM   #10
Super_HKS
Scooby Guru
 
Member#: 154434
Join Date: Jul 2007
Chapter/Region: NWIC
Location: USMC Land
Vehicle:
2009 WRX Hatch <@_@>
SWP

Default

Quote:
Originally Posted by Davenow View Post
but how do you KNOW its not leaking?

TurboXS valves in general work very well. Just gotta use the right amount of washers for your particular car.

Oddly enough, the normal type-H seems to work a little better than the RFL. I cant for the life of me see ANY reason whatsoever for this, they are identical other than the horn on the RFL. But the 3 RFLs I tested had to have an additional washer to hold the same as the normal type-H.
When I dynoed my car with the stock BPV and later with the turboXS RFL, there was no change in WHP and or boost. With the turboXS you just gotta make sure the gasket is lined up properly and you have the correct amount of washers.
Super_HKS is offline   Reply With Quote
Old 09-22-2008, 02:26 PM   #11
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default

that'll do it
Davenow is offline   Reply With Quote
Old 09-22-2008, 02:40 PM   #12
godforbid67
Scooby Specialist
 
Member#: 137168
Join Date: Jan 2007
Chapter/Region: South East
Location: ummm..... Andrewtech ftmfw!
Vehicle:
06 Built SGM WRX
35r, PPG, 280's, PSS9.

Default

good write up! the thing i never really understood though, was how a bov makes you a ricer. when i think of a ricer i NEVER think of them having a turbo (for the most part that is of course)
godforbid67 is offline   Reply With Quote
Old 09-22-2008, 05:15 PM   #13
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default

Ricer is a state of mind. You can have an F50 and still be a ricer if you do ricey crap to it and behave in a ricer kind of way.

BOVs make you a ricer just like owning an SRT-4 makes you a retard.

Its not that the valve or car are ACTUALLY linked to being a ricer or a retard. Its just that the majority of people WITH them, are ricers and retards. So it gets a whole bad stigma. Plus ricers, the first word out of their mouth when they think of a turbo car is "bov"
Davenow is offline   Reply With Quote
Old 09-22-2008, 05:59 PM   #14
KingOfSiam
Scooby Specialist
 
Member#: 84636
Join Date: Apr 2005
Chapter/Region: South East
Location: Atlanta
Vehicle:
2005 WRX (automatic)
Crystal Gray

Default

So.... BoV's are fine....?

I don't know what to believe anymore... everything I know could be a lie!

WHAT HATH YOU WROUGHT DAVENOW
KingOfSiam is offline   Reply With Quote
Old 09-22-2008, 06:09 PM   #15
Davenow
Scooby Guru
 
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar
Vehicle:
.

Default

See, I know its a confusing message.

They are and they arent. There are ups and downs. If you are worried about performance, and dont NEED the noise, its best to just stick with stock.

It all comes down to

What are you looking to do? Like how much boost, what kind of setup
What are you looking for? Noise?
DID YOU BUY A QUALITY VALVE?
If so
DID YOU ADJUST IT PROPERLY?

Its not that they are "fine" its that they are nowhere near as bad as people like to make them out to be. And that 99% of the time when someone is making them out to be bad, they are making statements that just arent true, and ignoring the larger problem of leaks.

rich wont hurt you. its a split second and its not that rich. LEAKS will hurt you. Less power, and can kill the turbo over time.
Davenow is offline   Reply With Quote
Old 09-22-2008, 06:18 PM   #16
Jubert69
Scooby Specialist
 
Member#: 167739
Join Date: Dec 2007
Chapter/Region: Tri-State
Location: CT
Vehicle:
04 WRX
ej207 spec C

Default

Quote:
Originally Posted by Davenow View Post
I made FAQs long before him.

And his FAQs are so out of date, its not even funny. Unfortunately he is just too busy to keep them updated, and as new things are discovered, and things change over the years, they become less and less useful. The other problem is that his FAQs are based on a compliation of posts on nasioc, AND his own knowledge. The unfortunate reality is that much of the stuff in his FAQs, is based on things that were never correct to begin with, because a lot of the threads the info came from, were wrong to begin with.


If his FAQs were working, there wouldnt be nearly the problems that there are. The problem is that his FAQs dont get straight to the point, and dump out a bunch of tech info that many people just dont understand or take the time to bother reading. This FAQ was made for ONE purpose. To get straight to the point, and try to squash some of the myths.


Not to mention that I know more about it the things I write FAQs on. 20 years automotive experience teaches you a few things
was just jerkin ur chain, good add to the FAQ though, i have learned a few things
Jubert69 is offline   Reply With Quote
Old 09-22-2008, 06:25 PM   #17
hustleshark206
Scooby Specialist
 
Member#: 182227
Join Date: Jun 2008
Chapter/Region: NWIC
Location: seattle, WA/ Jackson WY
Vehicle:
2000 MPS Built RS
1991 Leggy Turbo EJ22t

Default

good write up! Thanks Dave!
hustleshark206 is offline   Reply With Quote
Old 09-22-2008, 06:33 PM   #18
hustleshark206
Scooby Specialist
 
Member#: 182227
Join Date: Jun 2008
Chapter/Region: NWIC
Location: seattle, WA/ Jackson WY
Vehicle:
2000 MPS Built RS
1991 Leggy Turbo EJ22t

Default

So you are saying that if you are running under 22psi than having a fancy aftermarket BOV is pretty much useless except for the noise? Thats good to know because I certainly don't want to shell out 200+ dollars just for some noise. My car will be loud enough as is! Besides I like the idea of having a sleeper
hustleshark206 is offline   Reply With Quote
Old 09-22-2008, 06:46 PM   #19
smurfwrx
Scooby Guru
 
Member#: 151928
Join Date: Jun 2007
Chapter/Region: South East
Location: Columbia, SC
Vehicle:
09 Triumph S3

Default

well done. membership pre-requisite read supersticky for sure imo.
smurfwrx is offline   Reply With Quote
Old 09-22-2008, 06:56 PM   #20
mbaker
Scooby Specialist
 
Member#: 188614
Join Date: Sep 2008
Chapter/Region: SCIC
Location: san diego CA
Vehicle:
2004 WRB WRX wagon
VF-37 twin scroll on E85!

Default

good stuff!!! this is what i have been told all along from a tuning shop back in maryland. now my question for you is what do you think about turbosmart BOV's? i had one on my old car for a good 20k and it never had any problems.

mike
mbaker is offline   Reply With Quote
Old 09-22-2008, 07:42 PM   #21
RexTexWagon
Scooby Specialist
 
Member#: 150987
Join Date: Jun 2007
Chapter/Region: TXIC
Location: Austin, Tx
Vehicle:
2013 Ford Focus ST3
White

Default

Good write up Dave. I agree, Unas are great write ups, but hard to keep track of. Its like he works on a naval ship or somethin! lol

Very clear and to the point, and got the 99% of the newbie section questions answered on BOV.

I say tack this on to Unas?
RexTexWagon is offline   Reply With Quote
Old 09-22-2008, 08:14 PM   #22
itskrees
Scooby Specialist
 
Member#: 122277
Join Date: Aug 2006
Chapter/Region: MWSOC
Location: Skokie, IL
Vehicle:
2007 WRX OBP VF43
I turn cars into mirrors

Default

Mods please sticky this! Finally some straightforward raw information on such a common and misunderstood subject. Thanks Davenow.
itskrees is offline   Reply With Quote
Old 09-22-2008, 09:05 PM   #23
stud100spray
Scooby Specialist
 
Member#: 137141
Join Date: Jan 2007
Chapter/Region: Tri-State
Location: Armpit of America, USA
Vehicle:
2004 GSX-R600
Yeah, it's a track slut..

Default

Good write up Dave... This needed to be cleared up more than almost anything on this forum...
stud100spray is offline   Reply With Quote
Old 09-22-2008, 09:46 PM   #24
Kanatii
Scooby Newbie
 
Member#: 143171
Join Date: Mar 2007
Location: Conway, AR
Vehicle:
2006 Impreza WRX STI
Steel Grey Metallic

Default

I know you say compressor surge happens before the vent, but what is the sound that sounds like getting wiped out in mario kart that happens after the vent? I think its the valve "bouncing" open and closed as it vents? Is the spring too tight? Too loose?
Kanatii is offline   Reply With Quote
Old 09-22-2008, 10:29 PM   #25
Xigent
*** Banned ***
 
Member#: 185701
Join Date: Jul 2008
Chapter/Region: TXIC
Vehicle:
PSM WRX
20G 2.5L

Default

There have been 2 reasons I've been speaking against BOVs for the past few years.

1. Many have issues with leaking boost.

2. Loud BOVs are gaudy. People who have them (IE TXS RFLs, Greddy RS) are just after attention. Unfortunately they don't real that it's NEGATIVE attention that they are getting. While they think they are cool, everyone is rolling their eyes at them knowing they are just another ricer.
Xigent is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
General Subbie Newbie FAQ. Lets answer a few common questions and dispell some myths. Defiant Autospeed Newbies & FAQs 56 06-26-2014 12:35 AM
2.0L or 2.5L what are the ups and downs thewannab2002 Newbies & FAQs 28 05-27-2010 12:18 AM
The ups and downs of life MGXsport Off-Topic 14 09-10-2007 10:03 PM
S-AFC ups and downs y2k02scoob Factory 2.0L Turbo Powertrain 11 05-16-2003 05:21 PM
What are the ups and downs of a dog box- any brand? GT2WRX Transmission (AT/MT) & Driveline 23 08-06-2002 08:30 PM


All times are GMT -4. The time now is 01:34 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.