Ahhhh...I understand your question now
I remember reading about this a while ago. In the old day with the old carbie throttle body, all BOV were recirc...I can remember a reason for it. May be someone can help.

However, with the fuel injection and map sensor, it doesn't matter if it's vented to atmos or recirc. You will find that most aftermarket BOV are atmos vented because easier and it's more efficient since it does have to vent off into a small hose connecting to the intake.

 

I like the atmo vent BOV. It's noticable, scares pedestrians and make the car sounds mean. I guess it's the same reason as a sport exhaust system in the S2k.

One thing for sure is an atmo BOV is illegal in Australia. The anal politicians just make rules on what they dont like as they go along. They claim that the vent has got some oil vapor from the cam covers. However, even with aftermarket recirc BOV are deem illegal in some state as well. I think they just hate the noise as this give them more "complain" paper work from the public

If you are concerned about the legality of atmo vented BOV in the Vortech kit. It's easy to convert the Vortech BOV into a recir BOV anyway. The airbox (airfilter cover) has got an extra hole for this or alternatively you can drill another hole into the intake pipe. Get a 2.25" rubber hose to connect the BOV outlet and use a step down connector (I custom made this) for a smaller hose to route that back to the airbox.

Hey while typing this I have another idea Thx guys
I will get my mate to copy the Vortech intake pipe (between the SC and airfilter) with a metal pipe with 2 extra inlets. One for the exhisting cam cover vents. The other one, of 21/4" in size, for the BOV. That should keep the cops happy.

 

3ngin33r, your questions are not hard to understand. It's your primary assumptions (and others) that are hard to guess.

I might be wrong, but there seems to be an assumption that one of the reason you bypass boost to the intake is to drive the compressor. Hence this wouldn't make any sense on the SC as it is driven by the crank. This assumption is incorrect. Firstly, if you look at a centrifugal compressor design you will see that it can't be driven by pressure at it's inlet (at least not efficiently). Second, the bypassed gas is not directed into the compressor, but into the intake tract which has a free breathing filter at one end. The absolute majority of air goes out via the filter.

The sole reason you release pressure is to allow the compressor to keep spinning and not damage the fins or the butterfly. This goes for BPV's and BOV's.

The difference is simply a matter of taste. If you want a fart sound go for a trumpeted BOV. If you don't go, for a BPV. And of course there is also the artificial requirements of CARB and other bodies.

 

OK first, returning the excess pressure back into the intake track does not help keep the turbo spooled. The whole reason to return the air is for keeping the air/fuel mixture correct. As someone stated on a map senor car there is no need to do this.

3ngin33r1, the greddy type-s is a BOV, says it right on the box. I used my stock dump tube in my DSM to make it dump into the intake track, does this now mean it's not a BOV?

 

Thank you for the correction of my assumption.