i know different kind of BOVs has different higher boost limit (i.e. TurboXS H RFL holds @ 25psi), but what about lowest boost limit? or all BOV will blow off even psi is low like 4-7psi? did some research and couldn't find anything about it... thx and have a nice day.

 

the good blowoff valves will be able to hold pretty much as much boost as you can throw at it (boost holds the valve closed in the HKS SSQV and i think Greddy Type-S but im not sure which other ones have this design), and a sudden change of manifold pressure will cause it to open. so basically you don't set your BOV to pop off at, say, 20psi - you set it to open up when the throttle butterfly closes fast enough to send a shockwave back to the turbo which will stall the turbine.

(btw if you are thinking of something that limits your max boost level, that's a wastegate, not a BOV)

 

yes all BOV's will bleed off boost at any boost level no matter how low

 

thanks for the info, it helps. so i guess it's ok for me to get a Greddy Type-RS BOV for my car then, MSM max boost (limited by wastegate) is around 8.5psi. have a nice day.

p.s. i'm getting greddy profec b spec 2 soon too to dial the boost up to 10.5psi (any higher gets fuel cut by ecu).