What does a BOV do?
 

I know some of you guys are probably rolling your eyes on this one, but I am trying to learn, so please be patient with me as this is only my 2ND turbo engine.

How does a BOV (Blow Off Valve) work, and what does it gain?

I love my retro rocket and would like to get the most "bolt-on" power I can get. I am considering an Exhaust, possibly a CAI (Cold Air Intake)/Air filter, inter cooler plumbing and a future tune to get the most out of my aftermarket parts. I want to add all of the bolt-on parts before I consider a tune, thus my question on the BOV.

I spelled out some of the acronyms as I know that others like myself are not totally aware of all of them.

Thanks in advance,

As far as power goes, a BOV won't give you any extra power itself. It releases extra pressure from the system to help prevent boost spikes and overboosting.

Thats correct.

To my knowledge no one has one out yet. You could probably fit a universal one one if you didn't want to wait.

Based on the link from XXL. it doesn't sound like it will gain any power.
But, just telling people you have a "hooter valve" could be fun :o)

Thanks for the responses.

The purpose of a BOV is to give woodies to ricers revving at red lights.

And keeps you from grenading your turbo when you let off the gas and it wants to keep building boost. To that end, it should make you as happy.

The BOV you hear like that is vented to atmosphere. You can install an aftermarket BOV without all of the noise. Still, I guess I'm a ricer, because I think turbo noise is sexy. Also, ricers revving at redlights cannot build boost to cause a blow off unless they're driving automatics. The turbo has to be loaded to build boost.

Here's my brief explanation of a BOV. When you build alot of boost and close the throttle abruptly, such as when you shift (without using NLS) the turbo is spinning very fast and pushing alot of air through the engine. Then the throttle closes, and the still spinning turbo can build an enormous amount of boost in the piping due to the inertia of the turbine wheels. It can build so much pressure, in fact, that it can stop the turbine wheels almost instantaneously and damage the turbo. Thus, the blowoff valve is there to release that excess pressure and, as stated previously, keep you from grenading the turbo. A BOV is a supporting mod that allows you to run more boost, and just like many other mods in a turbo system, will not add power in and of itself.

Also, in a vent to atmosphere setup, a BOV requires tuning because it will cause the air fuel ratio to momentarily change drastically when the blow off occurs.

So, it sounds like it may be something that helps the life of the turbo, especially if boost is increased more than stock.
After reading the link XXL sent (thanks XXL), it sounds like a better solution is a compressor bypass valve (CBV) which vents back into the intake after the MAF sensor. This helps the ECU do a better job of adjusting mixture.
Why don't I ever hear about CBVs? Too expensive due to the extra piping required? Not as "cool" due to lack of the extra sound?