[wgknestrick]

Auto or not, it doesn't really matter.

Any car that has a throttle body, needs a BOV. When you close the throttle body, you are effectively sealing the charge pipe system. Problem is the turbo is still spinning around 80-100K (depending on size) RPM. This turbo rapidly, and I mean rapidly slows down to around 1K RPM (idle speed) in about .5 sec because the volume is fixed now and there is a pressure spike. This pressure spike in return acts on your compressor blades and wheel (newton's law is a biach) to slow it down.

Anytime you start putting big force spikes on any type of bearing, you are going to see failure.

This rapid decelleration is what causes the "compressor surge" or "wooble" noise on some cars. I had it bad enough to actually shake my entire car until I adjusted my BOV properly. That is the maginitude of force we are talking here.

No BOV cars may be running in strict drag apps, or by people "not really" knowing what they are doing. They may be fine now, but will be smoking their turbos soon enough.

One analogy I can think off is like trying to stop your turbo wheel at full spin by sticking something into the blades. Surge isn't quite this extreme because it is acting evenly over all the blades, but fundamentally the same.