Is your stock BPV (bypass valve) costing you power?
While the STI factory Bypass valve works great and we usually don’t recommend replacing it, it does have its limitations. We find the 20-22psi the factory Bypass valve can start leaking boost internally. Since it recirculating the air back pre turbo it’s hard to tell if it’s actually leaking or not. Sometimes a simple test can really show you what’s going on.
This dyno graph shows how much power was being lost due to the factory Bypass valve leaking boost. While tuning the car we felt it wasn’t making the power it should be. We took the factory Bypass valve off and installed a COBB Tuning Bypass Valve. With no other changes you can see we picked up 2.25psi of boost and a 24HP increase. These pulls had the same Ignition Timing, AFR, and Wastegate Duty Cycle.
Definitely a worthwhile investment if you are running more then 22psi or an upgraded turbo.