Ok i refuse to read all the other posts in this thread...skip it and get to my opinion.


BOV has 3 functions:

1. release excess pressure in the turbo piping when the throttle plate closes abruptly protecting the life the turbo by reducing the extra pressure created by this.

2. during a shift allowing the excess pressure to be released. when this is done there is no longer pressure working against the turbo allowing it to continue spinning without the extra pressure slowing the wheel down.

3. make cool sounds during shifting


Now a BOV and recirc are essentially one in the same. They open to relieve pressure from the turbo piping. A stock recirc or a BOV with a recirc line routes the excess pressure created back into the intake piping...after the MAF/MAS before the turbo. Since the air has been metered it needs to be kept in the system.

With an aftermarket BOV or a disconnected recirc the excess pressure is released into the atmosphere.

A stock recirc remains open when it sees vacuum from the manifold. This occurs when the throttle plate is closed enough (during a shift idle etc). An aftermarket BOV does the same thing but can be adjusted to how much it is open at vacuum and can be adjusted so it stays shut at idle. With the BOV setup like that the only time it will open and relieve any pressure is when there is boost in the piping and vacuum from the manifold (bascially only from shifting gears or abruptly lifting throttle).


Nissans eclipsestoyotas etc use maf/mas devices. They are not happy when they vent atmosphere during idle or low throttle activities.

Like said before the air is calculated by the maf the air escapes to atmosphere causing the vehicle to go rich dumping extra fuel. It is completely noticeable at idle low throttle driving and sometimes between a shift (depending on how much air is escaping.

Do yourself a favor hook it up in recirc and it will still be loud as hell. The greedy type-s on my Z must remain closed at idle and it only opens a little during shifts to release some of the pressure. Recirc would be the preferred setup.