Determining BOV Spring and other Vacuum Questions
 

Context:
JDL Kit-BOV sits on driver's side of intercooler
Tial Q BOV/I have a 12 PSI spring in currently, 8 PSI came with kit.
To my understanding, what I want is the lightest spring that will keep the valve shut at idle.


I do not have a boost gauge yet, so is my current line of thinking correct?::::


Take MAP at idle and subtract atmospheric pressure. My MAP usually stays within .29 to .31 and atmostpheric pressure at idle is always 101 from what I have logged.


0.3 BAR minus 1.01 BAR = -0.71 BAR which equals -10.3 PSI.


But, -0.71 BAR equates to -21 inHg


Which spring should be used, and are these normal/healthy vacuum levels? Also, I was using an STI PCV Valve but have since disconnected the hose between from PCV to intake plenum. The intake manifold plenum is now capped off. I plan on deleting the PCV valve and running a VTA catch can...and using the top of the plenum as vac for the BOV rather than the brake booster line. Will this affect vac levels dramatically?




http://www.tialsport.com/documents/w3_tial_qqr_sp.pdf

I had a heck of a time getting a tial to work on my turbo setup.

I tried the unpainted spring and it was too tight; the BOV would not function properly.

The white spring allowed the BOV to function, but then it was open at idle.

Basically what I had to do:
1) Run a dedicated line from the IM for the BOV (I used the same PCV line you mentioned)
2) Use the largest ID tubing that you can make work
3) Use the white tial spring
4) Shim the white spring with washers until its closed at idle

Basically what I had to do:
1) Run a dedicated line from the IM for the BOV (I used the same PCV line you mentioned)
2) Use the largest ID tubing that you can make work
3) Use the white tial spring
4) Shim the white spring with washers until its closed at idle[/QUOTE]




I feel dumb asking this, but what do you mean by "Shim the spring"...place washers underneath it inside of the valve?


Currently I am t'd off of the brake booster line...and the T that I have is certainly not 1/4 inch in diameter which I'm sure is contributing to lack of response time. Some are saying to get vac off of the purge valve under the intake mani....others are saying using the top of the intake mani that I already have blocked off.

10 PSI/Unpainted spring did the trick.

Proper Tial operation requires a Vacuum line at least 1/4 in size and less than 4 feet long coming from a dedicated vacuum source off the manifold. If you follow those rules, running the proper spring for your in/HG pressure will work.

I'm not a fan of shimming things personally. However some slight flutter in low RPM's is not going to kill your turbo, whats most important is that its functioning properly at WOT in higher RPM's with increased boost levels.

My setup flutters under 5k with anything less than half throttle. Running a -22 in/HG spring, anything less and its open at idle.

Other option is to get a different BOV.

do you have a reference as to what washers you used? I currently have the jdl kit with blow off on the passenger side and a plain spring that's 10psi. Stays closed, but not opening properly. Using 6mm ID hose. I'm thinking I go back to my white spring, but i remember before that it would be open during idle, so the shims would most likely do the trick.