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"The BIG BOV thread" (Where all bov question threads get merged)

2M views 12K replies 2K participants last post by  WRX-maniac 
#1 · (Edited by Moderator)
This is the big BOV thread. If you didn't find this thread, you didn't search.

This thread is where all BOV question threads get merged into.

The quote below in this first post is from our BOV info sticky and contains links to some very explanatory BOV information. Please take the time to explore the links before you ask repeated questions.

Thanks!


A stock WRX/STi comes with a BPV (Bypass valve) which is a vacuum-actuated valve designed to release pressure in the intake system when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake before the turbo.

An after market blowoff valve (VTA) does basically the same thing BUT unlike the stock unit it releases air to the atmosphere (giving you the loud sound). Some people see an after market BOV on a stock WRX as being in poor taste (probably due to the fact that it is basically a noise maker that really as no other benefit), while others simply find the sound very attractive.

Proponent opinions notwithstanding, there is a small mechanical downside to having an after market BOV (VTA) on a stock WRX. The problem comes when releasing air to the atmosphere that has already been metered by the mass airflow sensor. When the BOV releases (blows off), the ECU will be injecting the wrong amount of fuel into the cylinders. The engine temporarily runs too rich (meaning too much fuel is injected into the cylinders). This temporary rich condition isn’t typically THAT harmful, but it may cause bucking or hesitation on lift-throttle as well as some other concerns outlined in the links below.


Links for BOV info:

Sinister's BOV FAQ

Wikipedia

Unabomber on Nasioc

Davenow on Nasioc





 
#11,447 ·
NB question, just got a WRX 2012 and worried that if I do anything to it I may void the warranty, so want to be somewhat conservative here. For starters I would like to make the turbo spool louder, would you recommend using a BOV or installing an intake kit + mess around with ECU? I just would like to know what'd the safest way to go, in case the car needs to go back in Subaru and I put back all the original parts, I don't want them voiding my warranty!!

Thanks in advance!!
 
#11,448 ·
Snorkus delete.
 
#11,451 ·
Some says it does. some says it doesn't. I hear there is a counter and a way for them to check, but they aren't going to go digging into your ecu unless there is a serious issue. But if all your putting on is an intake and accessport you will be fine. You can literaly change the intake out in ten minutes.
 
#11,452 ·
For now, that's all I'm doing, I'm fine with the cobb intake and accessport, my friends tell me it's a good tuning parts company, if you think it's safe enough then that's good news and makes me feel better (even tho I do not know you haha, you seem to know what you are talking about). I'll try and do more double checking to make sure the dealer won't try to just void my warranty, I know sometimes they are just dying to do so. Thanks bro!
 
#11,453 ·
There is nothing wrong with the COBB "SF" short ram intake for any year or model of Impreza. It is well manufactured, has it's own R&D (it's not just a stolen/copied design), a decent sound, and from what I understand, decent filter element lifespan. I don't know if it is CARB exempt (California Emissions Standard), but it definitely shouldn't void any warranty... I've got a short ram intake as well, on a 2002 WRX sedan, and my extended warranty is still fine. It does depend on the dealership/salesperson. I will warn you, eBay knockoffs do not make friends in the service departments of Subaru dealerships. Stick with reputed brands with quality products, and things will go well. It IS wise to check here and NASIOC, etc., for advice on large purchases. A pound of wisdom and an ounce of gold goes a lot further than a pound of gold and an ounce of wisdom.

The AccessPort has advantages over "Laptop Tuning", failsafe programming in the AccessPort will prevent engine damage in many cases, some reflash programs do not offer any more than a disclaimer "we are not responsible if you torch your car with our device" type of stuff. Cobb also has a customer service department... RomRaider has a forum and a discussion group, etc... but I'd trust the AccessPort a lot further on a new car.

Some Subaru dealers have accounts with Cobb, and offer AccessPorts as aftermarket accessories right on the sales floor, along with tuning software services and some parts upgrades like exhaust and intake, shifter assemblies... ask your dealership's sales crew when a few salespeople are gathered. The group enthusiasm will help. Individually, salespeople may be shy about it because they know they are setting you up for more power, and older more conservative sellers don't like being responsible for that kind of after-market service since inevitably the increase in power will increase wear on the vehicle. Some dealers will also refuse to install anything that isn't Subaru of America branded with a part number... at which point it is possible to ask for a ProDrive ECU upgrade for about $10K... which will give you everything available with an AccessPort for 20x the cost... though I'm not sure if those upgrades are available on newer models... I know a bugeye can take the PD race ECU as a direct swap... wouldn't mind knowing if that is available for 2011+ STi?

Meanwhile... I am still stoked on the results of the 2010 STi intercooler with Greddy RZ bpv w/ RS hotpipe... silent. Quieter discharge than the stock BPV, even with the short-ram.
Also still using a Hallman remote ceramic MBC. 19psi on a PnP'd stock td04. lol

I am looking into new turbos... Since that's probably going to involve a V mount IC/Rad, I'll be re-installing the Greddy BPV, and will have more pics.
seems pics say a lot.

let's just consider this:

I get full warranty service, and any recall notice is served by our local Subaru dealer without question. The mechanics are all pleased with the upgrades, and no one feels the safety of the car is compromised, if anything, it is safer and more solid than it was from the factory... there ARE bad mods, just read before you wrench, and you will be in great shape.

as for a blow off valve on a Subaru... lol... until you are using a FMIC and are running 24psi, why bother....

WAH


psh.
 
#11,454 · (Edited)
Impreza2.0 said:
The AccessPort has advantages over "Laptop Tuning", failsafe programming in the AccessPort will prevent engine damage in many cases, some reflash programs do not offer any more than a disclaimer "we are not responsible if you torch your car with our device" type of stuff. Cobb also has a customer service department... RomRaider has a forum and a discussion group, etc... but I'd trust the AccessPort a lot further on a new car.
What are these "failsafe programming" features you speak of, which "will prevent engine damage"? The Cobb AP modifies the ECU the same way you do with a laptop/Tactrix: manipulating tables. As long as you're familiar with what you're doing, the Cobb AP is no safer than OpenECU.

Of course OpenECU isn't going to warranty anything. It's free software and doesn't offer base maps (it's up to the end-user to source a map). A tuner who creates OpenECU maps should offer some type of warranty / customer support, just like Cobb does. Cobb won't fix your bricked ECU free of charge, neither will Tactrix; I'm pretty sure Cobb charges more than the $75 that Tactrix does, as well.
 
#11,455 ·
AP vs Tractix...

the hardware are just interfaces people.. nothing more nothing less. for Pete's sake why does no one understand that??

Cobb will accept no liability beyond their own warranty. That said, along with the price you pay you do have the option of their forums, customer support (which is very good btw) and some really decent tuners that also utilize the cobb products.

Both are good interfaces, decide which one fits your skill level and needs.. and buy what YOU need.


SILLY RICER.. BOV'S ARE FOR KIDS
 
#11,456 ·
Holy **** man, thank you for taking time to write all this up for me, it is very helpful to a NB like me, and for that, you rock bro! BTW, whats under that hood simply looks SICK! How much did you pay for that intercooler? This setup seems very clean and neat. Since it does come down to the dealership and the salesman, how do you suggest I approach them to double check about my warranty??

Thanks!!!!! :D
Alex C
 
#11,458 ·
An intake that decreases filtration will not be fitted to my car. They need to prove via reproducible UOA data that particulates in the oil are the same or lower than when the authentic intake is used before I'll consider an imitation ("aftermarket").
 
#11,459 ·
Which means you'll never run an aftermarket intake right? ;) I don't think 99.999% of people that use them understand they all significantly reduce filtration of particles that increase wear on your engine. Then there's the fact those same 99.999% don't understand a dirty oiled filter is a better oiled filter and it works WAY better than a new or newly cleaned oiled filter, and you're not supposed to clean them very often. But I'd be preaching to the choir with you right? ;)
 
#11,461 ·
If somebody somehow invents a miraculous, impossible intake like that it would be very interesting! :)

It's not really impossible but you'd basically have to use a regular paper filter but a larger one than stock in order to increase airflow, along with a (effectively) larger, smooth hose like the aftermarket ones use. I've honestly never even thought about doing that but you raise an interesting question. There's a ton of paper filters on the market that are a lot bigger than a stock Subaru filter so it comes down to being able to build an airbox to accommodate one. This gives me an idea I want to try out now..... :)
 
#11,465 ·
need new BOV.

So i have been having this problem, boost usually reads 16psi now only read around 5 to 7psi, ppl been saying boost leak, but i took to subaru dealer and they said my awesome EBAY BOV the previous owner bought, is faulty. so now im in the market for a new one. im looking at either PERRIN or a turboXS rfl BOV. which of the 2 would be better?
 
#11,466 ·
So i have been having this problem, boost usually reads 16psi now only read around 5 to 7psi, ppl been saying boost leak, but i took to subaru dealer and they said my awesome EBAY BOV the previous owner bought, is faulty. so now im in the market for a new one. im looking at either PERRIN or a turboXS rfl BOV. which of the 2 would be better?
If your choice is Perrin or TurboXS...now doubt Perrin. Much better quality. We sell them as well.

Perrin Performance : Kronos Performance, Fueling the Car Lover Within
 
#11,471 ·
I can tell you with almost certainty what happened. You bought this car used. The previous person modified it. They tuned for it. They wanted to sell it. They sold their manual boost controller and hooked up the old vacuum hose. But they had taken the restrictor pill out of it because they didn't use it with the boost controller. Now your car is tuned for a manual boost controller, but you don't have one in.

It's not 100%, but I've had about 10 guys that have had this problem over the past couple years that I've helped fix it.

The only way to be sure if I'm not lying to you is... Get someone with a tactrix cable (or if you have an accessport) download logs, and see if your WGDC (wastegate duty cycle) is 0. If it is... then what I said is correct, and you can either put a MBC on the car, or have the car's tuning adjusted after you install a restrictor pill. ALSO... make sure your vacuum hose DOES have the restrictor pill in it. Some idiots don't tune for the MBC, and just pull out the restrictor pill, and throw a MBC on it.

DONT install a manual boost controller without checking on this first. You might make problems worse if I'm not correct.
 
#11,480 ·
search some more.. you dont want air exiting to atmosphere in a metered air car (where ecu meters incoming air to determine air/fuel mixture) .. it plays hell with the ecu.

We also have a factory B P V .. bypass valve.. If you want to upgrade that there are a few but my question again would be why? The factory valve hasn't cost you anything and will hold up to ~25psi .... Or, as Adam asked, do you just want noise?
 
#11,483 ·
mangostick said:
The factory valve hasn't cost you anything and will hold up to ~25psi .... Or, as Adam asked, do you just want noise?
Good luck running 25 MRP through a plastic valve that comes on the '08+. Many of them leak @ StageII levels.
 
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