General BOV question

[Technohedge]

Hey guys, so I got a greddy RS type BOV (its a copy) to chuck on the caldina just to see what it did. (Ive heard a few peeps have issues with aftermarket BOV, so didnt want to fork out for a 'proper' one till i know its gonna work).

Anyhoo, when installing it i noticed that the stock BOV was set up differently to how i have seen most installs on BOV of this type:

Usually the pressure side is connected to the underside of the piston valve, and the pressure pushes open the valve against the spring pressure (vacuum assisted). This seems to be how most are set up?

The stock one has it the other way around, with the pressure side keeping the valve closed and the vacuum sucks open the valve. So i installed mine this way to see what it did.

Seems to work fine? no surge and opens nice same as the stock unit. I hear people have trouble setting them up when installed the traditional way due to boost leaks from light spring pressure? Seems like boost leak wouldnt be an issue with it this way around?

Its slightly open at idle (presuming cos of the vac in the lines) and air is coming OUT of the partially open valve. When throttle is depressed it sucks for a brief second before closing solid. (having thoughts of putting a small filter on the outlet to stop crud gettin in there on the brief vacuum before it shuts).

Should I turn it around or will it be ok like this?

[GDII]

I think the spring preload should be set stiffer to hold it shut at idle.
The valve should not open under boost due to the equal pressure on both sides. Boost from the intercooler and boost from the vacuum line cancelling out the pressures making it remain closed.

This might help for the idle part.
https://www.youtube.com/watch?v=KgGRfR6jt-c

This might help figure out what way to have the valve installed.
https://www.youtube.com/watch?v=cTMwtvZtpGA

The stock BOV has vacuum to the top AND bottom of the diaphragm holding the valve closed while under boost. When the vacuum lines see vacuum the boost pressure from the intercooler forces the valve open releasing pressure. For the RS valve it would be best to have the boost from the intercooler going into the bottom rather than the side as it is meant to force the valve open from the bottom when the top of the diaphragm sees vacuum.

[Technohedge]

I agree ill have to mess with the spring pressure to get it closed at idle.

However if you think about the situation at idle:

Top of the valve diaphragm sees vacuum from the manifold, the valve itself sees slight pressure from the intercooler piping. The valve wants to open, but spring pressure (if set correctly) should be keeping it closed.

If you have it the (wrong?) way round like i have, then the slight pressure from intercooler piping would actually be helping to close the valve as it is acting the same way as the spring.

The way i have it at the moment is (as far as I can see) the same way the factory unit does it.

[Al]

Just remove it and run no BOV.