uhh yea..... what do they do other than make the cool sound?

 

They release excess boost pressure when you close the throttle. Lets say your shifting gears, you take your foot off the throttle. THe turbo is still spooling since there is still exhaust flow. SInce the throttle is closed the air cannot go through the throttle body. THe BOV opens and releases the air into the atmosphere. If you didn't have a BOV the boost pressure would go back to the turbo and slow it down.

 

slow it down or stop it then you will break the shaft between the wheels and shell your turbo meanwhile throwing chips or steel and lots of oil threw your motor. They are driven by vacume lines.

 

I suspected that a lack of blow off valve could do serious damage to the turbo, but i wasn't sure so i didn't write anything about that. Thanks for the clearfication.