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.
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.
The closest I've done to a performance mod is removing the intake silencer. Soon I'll be ordering a downpipe. The kit fits perfectly and required no adjustments for me. Maybe others tried to adjust it or something.
The BOV itself would be the same. And since either one fits, I'm assuming the base pieces used to bolt it on are the same but just listed differently so the STi guys don't have to ask if the WRX kit fits.
I also said it vary's from car to car. Do this on an MR2 and they run so rich they have shut off mid-shift. Its an explination of what is going on, I never said to get rid of you bov
Its simply information for people that wonder why this happens when they switch to an aftermarket bov not a "Sell your BOV's now" Statement
The BOV itself would be the same. And since either one fits, I'm assuming the base pieces used to bolt it on are the same but just listed differently so the STi guys don't have to ask if the WRX kit fits.
The HKS BOV, IMO is a better bov compared to spring loaded (Push vs PULL) BOV's. It reacts very quickly to pressure changes, a very good quality BOV IMO. The running rich/lag issues depend soley on how much fuel your computer dumps compared to how much escapes when you shift.
I also said it vary's from car to car. Do this on an MR2 and they run so rich they have shut off mid-shift. Its an explination of what is going on, I never said to get rid of you bov
Its simply information for people that wonder why this happens when they switch to an aftermarket bov not a "Sell your BOV's now" Statement
The thing with the MR2 shutting off sucks dude, sorry to hear about that. In my observation, the STi isn't much affected by it. My mileage has remained the same, lag (what little there is) has not been increased at all, etc.
I know you didn't mean to sound like you wanted us to get rid of the BOV if we had one already...sorry if I came across that way. It's also easier to switch between stock and aftermarket or vice-versa if you can install it yourself...so if it doesn't work you don't have to pay someone else to swap again. Excepting for one clamp, mine was a 20 minute install. Rant over.
To install a BOV, you need: hands, tools to loosen and tighten the bolts (good ol' socket stuff), patience and the BOV kit. One person can easily do it, but two make it easier with some of the @#$% stock clamps on the hoses. The HKS kit comes with good instructions and even includes the plug for the recirculating hose.
Does anyone have the Blitz BOV installed on their STI? Did the installation cause any problems? and how is the BOV performing now that it's installed? I have searched for this but it seems that there are no Blitz BOV for the STI right now and i like that sound the best, any info would be greatly appreciated.
I ran the Blitz DD on my STI for about 1 month. At low RPM's, I did experience some strange idle characteristics no matter how much I tried to adjust it.
Most of the BOV's should work on the STI with the addition of shims if necessary depending on manufacturer. However, you will probably be more satisfied with a BOV that does have some recirculation such as the WorxTuning or TurboSmart.