BOV spring issue

[spf_lexus]

Just picked up a TIAL BOV and have a question. I am supercharging and they rate their springs based on the LS400's vacuum strength, here's the breakdown on their site:

Blow Off Valve Spring Options
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Engine Vacuum Reading Range ​

Spring to Use ​

-22 through -23​

-12 PSI​

-18 through -21​

-11 PSI​

-14 through -17​

-9 PSI​

-10 through -13​

-7 PSI​

What im wondering is this... it came with an 11psi spring but I have no idea what the 1uzfe vacuum range is. Just in case I have a 9psi spring coming too. Dont know if it makes any difference but the system will be running a 6psi pulley. Does anyone know this range?


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[stevechumo]

If you run a low to mild boost, then a soft or low BOV spring will be good. The BOV needs to be as soft as possible, but enough to hold it closed under normal condition and boost. Many of the BOVs have adjustable screw that you can increase or decrease the tension so you adjust it to your desire. My opinion is to get the lowest spring, then you can adjust the screw to make it tighter.

 

[spf_lexus]

thanx steve but isnt the idle/cruising more important with a centrifugal setup than a turbo? I mean if the charge pressure ever gets too high at idle/crusing the 11lb spring will open... but if im driving it under WOT then it will eventually build on its own boost of 6psi w/ 6psi pulley until 11psi is reached right? I just want to know that test driving this thing tomorrow will be safe with an 11lb spring and a 6psi pulley. I ordered a softer spring for later this week but I will have my belt before then and would like test drive. any ideas?

 

[spf_lexus]

Oh i forgot to add... these TIAL bov's DONT have an adjustable screw type. So the only way is specific spring rates.... guess if i up my boost aler the 11lb will be handy. that chart above is what they offer.