[Greenguy]

There is the ECU, relief valve, Blow off valve and throttle body.
The ECU send a 12V signal to the relief valve, by doing that the relief valve open and send pressure to the BOV valve and that keep it shut so pressure is built in the intake chamber, When the ECU want to relief the pressure it cut the 12 V signal to the relief valve by doing that it bring vaccum to the BOV and that make it open so it relief the pressure. The BOV opening depand on the vaccum pressure from the throttle body so the more vaccum you have the more oppening you get from the BOV.
The BOV is not ajustable so it is really the ECU via a pressure sensor that control the pressure.

 

[GoFaster]

Yes, and as noted in the other thread, the vacuum that can be used to open the valve will only exist under part-throttle or shut-throttle conditions. At wide open throttle, there can be no source of vacuum to the switching valve (because there is boost pressure everywhere inside the throttle bodies), so the bypass valve can only be closed.

Of course, if the ECU is commanding part throttle as its means of restricting the power output, part-throttle conditions might exist in situations where you might not expect ...

 

[Greenguy]

Yes, and as noted in the other thread, the vacuum that can be used to open the valve will only exist under part-throttle or shut-throttle conditions. At wide open throttle, there can be no source of vacuum to the switching valve (because there is boost pressure everywhere inside the throttle bodies), so the bypass valve can only be closed.

Of course, if the ECU is commanding part throttle as its means of restricting the power output, part-throttle conditions might exist in situations where you might not expect ...

I didn't realise that all the info was already on Garth285 previous post. I am use to work alone and sometime I read with my mind shut. Sorry for that

 

[H2QIK]

Has anyone tried to modify the blow off valve to get a louder sound from it. Should would like to be able to hear it over the exhaust.

 

[Giggity]

Has anyone tried to modify the blow off valve to get a louder sound from it. Should would like to be able to hear it over the exhaust.

Duck call is the way to go.
https://www.youtube.com/watch?v=CIvJhjY03WY

 

[H2QIK]

Lol, there are some creative people out there...

 

[garth285]

Has anyone tried to modify the blow off valve to get a louder sound from it. Should would like to be able to hear it over the exhaust.

The vent tube from the BOV just runs back into the airbox and you could let it free breathe since it only open to expel air. just make sure you block off the hole on the airbox.

 

[BobC]

.......When the ECU want to relief the pressure it cut the 12 V signal to the relief valve .....

In other words it fails safe.