# BOV only opens up at high rpm/ high psi...

**URL:** <https://forums.speedlife.net/t/bov-only-opens-up-at-high-rpm-high-psi/146069>\
**Category:** Canada Nissan Automotive\
**Created:** [March 7, 2007, 11:17pm UTC](https://forums.speedlife.net/t/bov-only-opens-up-at-high-rpm-high-psi/146069 "2007-03-07T23:17:54Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![AdamP](https://avatars.discourse-cdn.com/v4/letter/a/b19c9b/32.png) [@AdamP](https://forums.speedlife.net/u/AdamP)\
**Post date:** [March 7, 2007, 11:17pm UTC](https://forums.speedlife.net/t/bov-only-opens-up-at-high-rpm-high-psi/146069/1 "2007-03-07T23:17:54Z")

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I just installed a Blitz SS BOV on my S13.

I have a few questions regarding the tuning.

I rev the car just standing under the hood and looking down into the BOV.

Loose setting:  
Mild revving, the is a deep rattlesnake-like whoosing in the pipe. The blow off valve piston is not moving at all.  
Medium revving results in some more whooshing (surge I believe) and the BOV is still not not moving.  
Some harder revving releases the blow off valve but only a little bit.

Medium setting:  
Mild reving - the whooshing in the pipe is more of a continuous sound, the BOV piston isn’t moving here.  
Medium revving results in a louder whooshing sound with a bit of resonance inside. BOV piston isn’t moving.  
Hard revving opens up the valve. Loud.

I’ve adjusted the screw from very long (loose) to very short (tight) and I have no idea what the correct setting is.

Shouldn’t be BOV piston open up a little bit even if it’s making like 2-3psi boost at the time?

Could there not be enough vacuum? On this particular vac line I have the fuel pressure regulator and the BOV. On the SR20DET how many vacuum lines do I have and which ones can I use?

_When driving (under load):_  
When I rev the car up hard under load in 1st gear up to 6000RPM+ the BOV opens up and is loud.  
Continuing onwards, there is about 1s lag (foot to the floor) and in 2nd gear. At 6000RPM+ the BOV is barely releasing any air. I am running full boost (7psi) because I am WOT and I can definately hear it spooled.  
From third gear, WOT and letting off there is no BOV sound. I just hear a deep whoosh. Any ideas?

My ARC Super BOV also behaved in the same way so I think it may be a weak vacuum.

I am going to get the recirculation kit as soon as I can find one for this BOV but for now I want to know why it isn’t opening at very small psi? Maybe if anybody has any vacuum hoses kicking around I might pick those up to replace a few of my lines.

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**Author:** ![onefast87](https://avatars.discourse-cdn.com/v4/letter/o/4af34b/32.png) [@onefast87](https://forums.speedlife.net/u/onefast87)\
**Post date:** [March 10, 2007, 1:16pm UTC](https://forums.speedlife.net/t/bov-only-opens-up-at-high-rpm-high-psi/146069/2 "2007-03-10T13:16:11Z")

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first of all make sure you not T’ing your BOV, try to get its own line to the intake manifold.  
second,if your only running 7 psi,then the screw should be farely loose  
third im almost sure that the piston shouldnt open unless boost is happening

good luck with this