It seems that a lot of Evo and other turbo owners in general own aftermarket BOV on their vehicles. With such a high percentage of owners I was wondering why the OEM Manufacturers dont include them with the vehicles? Unless the stock cars have some type of silent BOVs. Are BOVs necessarry or is it just a woosh thing?

 

On a turbo vehicle they are very necessary and OEM manufacturers do include them, they are commonly referred to as Air bypass valves and they are designed to let excess boost out when the throttle is closed so you don't blow stuff apart, that is why you hear them when you let off the gas, like during shifting. Most ppl change them cuz they are running much higher boost then stock and NEED an aftermarket one to hold the higher boost.

 

they are necessary and you have one. most people just like that whoosh sound. stock pieces are so underrated. youll have so much more fun using your car than adding rice boy parts, why cant people understand this?

 

necessary?? yes , necessary to upgrade??? not entirely, but to each their own

 

It's a cool sound if you aren't worried about attracting cops. I don't think anything over stock is necessary ... maybe if you are running higher numbers though?

 

Good info. Definitely learned something, since this is my first boosted car. Well since Im not planning on pushing the engine too much I guess the stock set up is more then enough for now.

 

If you want the whoosh sound then just change your intake and you will hear the stocker.

 

Agreed. All you need to do is add a drop-in filter or intake setup from AMS, Buschur, Injen, etc. and you'll hear the whoosh sound you're looking for. No need to spend all the money on an aftermarket BOV unless you're running a boost level much higher than stock.

 

I have to agree with this. Some BOV even have sort of sound amplifier just for sound effect!!!

Not unlike why most aftermarket exhuast tip(s) are acsending(tappered) out to make them larger.

 

alot of people also change their bov's because many stock types bleed air and cannot hold boost well at stock boost levels causing erratic dyno graphs, and the turbo to work harder to maintain boost. for example mazda's bov's leak and have been dyno proven hp robbers and when replaced have shown consistent graphs and slight gains of hp and torque. i questioned one of rep's and his response was " it's a calculated leak figured in by mazda", nice huh.

 

I don't think I ever heard this for Mitsu valves... however, you can replace it for sound, looks, or more adjust ability if you like. No HP or TQ gains in the X.

 

Back when my friend first got his mr2 and did the turbo swap, he was driving around and some people pulled up next to him at the stoplight and asked if he had the "air shifter." It was hilarious. A lot of people don't understand what a blow-off valve is.

You don't need an aftermarket BOV on your car. It comes with a stock recirculating BOV that is fine. I doubt you need one until ~400whp.

I have the HKS SSQV on my RSX, but prefer the recirculating BOV on the X since it makes no noise.

 

no, not saying hp or tq gain on the X but to answer op's Q, and give an example. mitsu's 2nd gen eclipse/talon stock plastic bov's leaked as well, which is why people switched to 1st gens.

 

Yes, I now recall this.

 

I not really looking for the woosh sound. I was just asking in general, since so many people purchase aftermarket BOVs. I did not know that a BOV that leaks can affect power delivery. Yet another thing I learned today.