WRX Info

$0.16 Blow Off Valve Modification

Very cheap and stealth this fit the bill perfect. Still 100% recirculate so no idle problems or rich between shift problems. This will allow you to run as much boost as you can throw at it and not open. The one drawback to this that I have found is that around 5-10psi when you shift you will get a real quick real short surge. This will not happen at higher boost levels.

The Mod:
Take off the BOV and look at the face that mounts to the IC. You will see two holes a big one and a small one. The big hole is the valve that releases the pressure the small hole is a boost signal line.
What I did was to take a 1/4-20 tap and drilled out the small hole and tapped it. Be careful to not let any shavings go into the hole. I held the BOV upside down while drilling and tapping. Then I took a 1/4-20 set screw put Teflon tape on it and sealed off that hole.

Block This Hole

Then on the body of the BOV you can see where that signal hole goes through the casting. You want to drill in to that signal line and vent it to atmosphere. There is a bung cast into the BOV body to do this.

Drill This Hole