The purpose of the valve is to bleed off air when the throttle body is closed. Trying to get the vale to be shut at idle is not a good idea

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I think you're spring is too stiff and don't think you should go stiffer because you're supercharged. There is a pink spring for supercharger applications. Are you measuring your vacuum at idle? As a comparison, my car idles at ~27kPA which is about 7.97inHg. The "-11 Psi (-22 in/Hg )" spring would be too stiff for my supercharger setup.

 

Is this a blower specific case? I'm not sure I like the idea of unfiltered air getting in

 

The air needs to go somewhere when the thottle plate is closed.

 

The throttle plate is never 100% closed at idle; otherwise the motor would die. Also, at idle the blower is barley generating any boost.

I'm pulling ~20 inHg at idle, which places me at the 11 psi spring.

 

The valve is supposed to be open at idle with a blower. What did you use to determine 20inHg?

 

Do you have any reading material where I could understand why a BOV should stay open (by design) for a supercharged application? I'm trying to understand pros vs cons. Based on my online research, people do it both ways.

20 inHg was reported by my boost gauge (and confirmed by the MAP sensor).

 

I do not have any material at the moment.The blower is ALWAYS spinning, that air needs somewhere to go other wise it will go past the "partially opened" throttle plate at idle and raise the idle.Oh, and if you ever feel like going back to the bypass valve flange and don't want to re-weld it, Ill trade you my aftercooler and we can work a deal

 

The throttle plate is closed, but the IACV will keep the engine running. Like rain h8r said, you need it open at idle. It will NOT suck in air, as the blower will be forcing air out of it. It's also the reason most kits use a diverter valve. It keeps you from having a constant hiss off-throttle.

 

What confuses me is that why does the BOV need to stay open for blowers but closed for turbo applications? Turbos also provide (very low) boost at low RPM.

I emailed Tial inquiring about which spring I should use. They stated for a supercharged application, run the 2 PSI spring as it needs to stay open at idle.

Can anyone explain why to use a 2 PSI spring vs the 10 PSI I'm running now. They're both open at idle.