boost+spring > boost. so it always stays closed even without a very stiff spring.
***Exactly. It is just like a simple arithmetic equation.
boost pressure (IC) + spring pressure > boost pressure (manifold)
The boost pressures cancel each other out. The only thing left over holding the valve closed is the force of the spring. We are in agreement on this point. Even a very light spring is enough to keep the valve closed under high boost pressures.
o vaccum + spring < boost
***The above equation makes no sense at all. You are saying that on your very special BOV you can have none of the nipples attached and the BOV will operate correctly. You must have a magic BOV then.
Lets assume you are running the BOV with *neither* of the nipples attached. Then under boost you will have the following:
boost pressure (IC) > spring pressure
If you have a street spring adjusted softly the valve will be open under boost during acceleration. This is not desirable.
If you have a race spring adjusted stiff then the valve will be closed under certain boost levels. Then when you shift gears the valve will still not open. What force will act to open the valve if you do not supply vacuum to the upper nipple?
Why is there such a big debate on how to hook up a BOV or how to adjust it? This thread has been around forever on several message boards and there are so many opinions. The correct answer is never revealed.
Well here it is:
For a bypass valve rerouted to the intake on a MAF equipped car set the valve to open easily at around 10-15 inHg of vacuum.
For a bypass valve (or BOV) open to atmosphere on a MAF equipped car set it to open at greater than 22 inHg so that it is closed at idle.
For a BOV on a MAP based car open to atmosphere set it to open at greater than 22 inHg or set it soft to open at 10-15 inHg and use a small air filter on the BOV so as to not allow unclean air into the BOV under vacuum conditions like during part throttle cruise.
Of course there one last way I do it on MAF cars. I set the spring to open soft at 10 inHg with a street spring. With a Type S I use only the inner spring and discard the outer one. Attach the upper nipple to vacuum. Attach the lower nipple to a boost signal that is regulated by an on/off solenoid which allows boost to reach the lower nipple only when the throttle is closed. Use a microswitch attached to the throttle body linkage or a circuit that monitors TPS voltage to open/close the solenoid. This way will cause the valve to open even faster and the blow off sound will be louder as well.
Next.