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Old 03-02-2015, 01:30 PM   #726
StiFry83
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Default BOV FAQ: The REAL dirt on BOVs. Ups AND downs. Lets dispell some myths.

Ok, I'm very new to the whole turbo scene. That being said would anyone have advise on what's best for a stock 2015 sti?
I have planes to get catback and intake in a few months but that's about it.

I've read a lot of the info on this thread but im still confused.

What I have gotten out of the thread is, that bov's used properly have very little if any negative impact on the vehicle.
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Old 03-27-2015, 11:27 PM   #727
STIL3TTO
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Thank you!
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Old 03-27-2015, 11:29 PM   #728
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I have been considering a Tial for my 2007 (Perrin kit) STI. What is your feedback on why it's the best?
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Old 04-05-2015, 01:06 PM   #729
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Tial is pretty much the best on the market. Just make sure everything is installed properly. Make sure whoever installs it does a smoke test afterwords to make sure there is no vac or boost leaks.
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Old 04-07-2015, 09:44 AM   #730
mlopez209
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So I really love the sound of the HKS SSQV, but you guys don't recommend it, I like taking advice from people who know their stuff, so if I were to buy this BOV(the legit one) for my 05 sti, am I gonna regret it? My car is stock w/ cobb exhaust.
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Old 04-10-2015, 11:43 AM   #731
su_ba_roooo
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Good read. We really enjoy our Turbo XS BOV.
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Old 04-13-2015, 06:19 PM   #732
PatPHL
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Hi. First post from a first time suby owner. Is replacing the stock BOV going to hamper my WRX CVT in terms of performance? should I have it tuned after I replace the BOV?
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Old 04-13-2015, 06:27 PM   #733
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Quote:
Originally Posted by PatPHL View Post
Hi. First post from a first time suby owner. Is replacing the stock BOV going to hamper my WRX CVT in terms of performance? should I have it tuned after I replace the BOV?
if you replace your blowoff valve it must be recirculating due to the di engine/twin scroll. changing a diverter valve does not require a tune. because of the recirculating valve you will not get the WHOOSH! sound you're looking for. if this is your first mod on a 2015 get a muffler delete or something else. this is not a worth while mod on our cars. well its not worth while until you've got a vband turbo/tial setup...but you're not there yet.
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Old 05-05-2015, 03:05 PM   #734
GotMeUnderPressure
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I can't believe you guys are so down on ricers.

Do you also deny that "Humor is the best medicine"?

http://i.imgur.com/fgiQOT3.gif
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Old 05-05-2015, 05:03 PM   #735
sc00by4life
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Quote:
Originally Posted by powder8 View Post
if you replace your blowoff valve it must be recirculating due to the di engine/twin scroll.
this is not the reason, nor have anything to do with it.
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Old 06-02-2015, 01:02 PM   #736
Haakaflocka
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Quote:
Originally Posted by Xigent View Post
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.

opinions are opinions
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Old 06-02-2015, 01:09 PM   #737
Southern Boost
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My stock BOV on my 08 WRX is loud as **ck. Dont see why I would ever need to swap it unless i go beyond 20psi. Ill spend that money elsewhere.
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Old 06-04-2015, 07:17 PM   #738
mpesci10
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After further consideration a bov is no longer in my future
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Old 06-29-2015, 11:16 PM   #739
WeidMan
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Quote:
Originally Posted by Davenow View Post
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.
Good read
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Old 06-29-2015, 11:20 PM   #740
WeidMan
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Quote:
Originally Posted by GotMeUnderPressure View Post
I can't believe you guys are so down on ricers.

Do you also deny that "Humor is the best medicine"?

http://i.imgur.com/fgiQOT3.gif
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Old 07-13-2015, 04:19 PM   #741
Sisko33
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To the OP, Dave. Did you test any Turbosmart valves? The one specifically I'm asking about is their Kompact Recirc valve.
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Old 07-19-2015, 01:40 AM   #742
Jin.
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Thanks for the info. I'm new to the subie world.
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Old 07-19-2015, 02:50 PM   #743
SpeedyG620
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First mod on my 15 wrx is going to be cold air intake, should i replace the factory charge pipe at the same time or does it not make a big difference?
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Old 07-20-2015, 09:05 AM   #744
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A cold air honestly doesn't do much for you under 400ish hp. But you can hear the whooshy noises of the turbo better if that's what you're going for. Unfortunately I'm not able to answer your question though, but you may be able to find more info on a more applicable thread. This one concerns BOV/BPV.
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Old 07-30-2015, 07:10 PM   #745
hawkeyepoorguy
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Hey so when i bought my o6 sti it came with a bov. I don't know what kind but i really think it's awesome i never owned a car with boost before. it feels nice to hear. Thanks for the info dude
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Old 08-02-2015, 08:37 PM   #746
PNWsubie1
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So, pros and cons evenly considered, what would you recommend to be the best BOV? one that will keep your MPG's from dropping, that dont leak on stock boost and have a crisp sound to it? i know you gave brands but what model?
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Old 08-03-2015, 09:57 AM   #747
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Honestly its been so long since the test I couldn't tell you. I would feel confident in recommending any of the same ones I recommended before. There are probably some decent ones now.


Also, it feels awesome that this thread is still alive and putting info out there this long after.
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Old 08-18-2015, 02:15 PM   #748
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Great faq very informative!
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Old 08-26-2015, 07:13 PM   #749
zhonghuihe1225
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good stuff right here
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Old 09-09-2015, 01:56 PM   #750
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great read, lots of helpful information!

Thanks, Dave.
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