You should see the most normal vacuum at idle, when you want it stay closed. Vacuum will be slightly higher at high decel, which is when you want the valve to open, and boost pressure helps force it open as well. The only time the valve is open the engine should not want much air at all.

 

From my experience the decel vacuum can be almost double idle vacuum. With my current setup, idle is 15 inHg and decel can go up to 26 inHg, if not more. At idle or decel is the turbo moving enough air to blow air out of the BOV so unfiltered air can't get sucked in?

 

At idle no but the spring should keep it closed. During decel yes and you want it open. When you are out of decel it will close again.

 

Just to clarify, the Tial "white" spring that I bought is stiffer and thicker than the spring I am using that came with the BOV. So I do not think shimming the white spring will fix it. It is already too stiff which is causing the flutter. The heavy spring that came with the BOV is thinner and much easier to compress, this the reason the valve is hanging open.

 

http://www.tialmedia.com/documents/BOVspc.png

If your vac is 18-19 u need a Plain.

 

According to that chart, is the plain spring stiffer than the white spring? Looks like it...

 

That is correct. Just pointing out that is the one for your -18 to -19 vac. Is this flutter your experiencing at part throttle to half throttle bursts or at wot? Mine does it at part throttle bursts with an rps 50mm

 

The flutter is at half to full throttle as soon as I let off the gas. I think a stiffer spring would make it much worse.

 

Are you making boost half throttle? Depending on the amount of boost to vacuum the bov might be bouncing might not. Aslo the valve could be sticking a little; take a part and oil the guide, as weill as check the piston sealng area, and make sure there is no sticky stuff there.

It is a balancing act between to much and not enough spring. Also the amount of boost to pop the piston off its seat. While 10psi might blast the piston off the seat, 4 might not cut it. This is why the spring is usually set to max vaccum or slight below max vacuum.

 

According to the Tial chart you should be using the Plain spring based on your 18-19 vacuum but that one is stiffer than the White one you are currently using so it would give you more flutter. The one you have now should be opening with your 18-19 vacuum and like Ferocity02 posted at decel you should have even more vacuum than at idle.


The turbo kit I installed came with a Dark Pink(stiffest) spring which is good for -20-21 vacuum but the cam in the car only gives it -9 at idle so I was going to buy the Black(weaker) spring.

What are the color of the 3 springs you have now?