in running my greddy R i have gotten mine to open at 0 vaccum and 15psi of boost on the other side. you can over ride the standard spring.

***I would *not* recommend supplying boost to the lower nipple of the BOV. It sounds like that is what you are doing. The only reliable way to do this would be to supply vacuum to the upper nipple and then supply boost to the lower nipple that is regulated by a solenoid. Have the solenoid supply boost to the lower nipple only under closed throttle conditions. That way vacuum will suck the valve open and boost will help push it open as well. This way you will not open the valve prematurely and cause the turbo to overspin.

If you have teh Racing spring in then yes i would reccomend setting it softer.

***On MAF equipped cars the street spring is the wiser choice. You want it to be easy to open the BOV.

Remember if you have only the upper nipple attached to vacuum the valve will stay closed even under very high boost levels. Under boost boost pressure will be trying to open the valve from the intercooler piping. Boost pressure will also be trying to close the valve from above via the vacuum line. Therefore these two forces cancel each other out. Lastly you have the force of the spring keeping the valve closed. So when you have only the upper nipple attached any spring stiff or soft will be enough to keep the valve from popping open.

With your Type R do you have one or two ports connected?


anybody that is blowing huge cfm from a good sized turbo will immediatly open the bov regardless of the spring.

***Not if only the upper port is attached to vacuum!