Perrin Recirculating Plumb Back BOV Red Bank Vs. Credit Union: Which Is Best For You?. This is the PERRIN Recirculating Blow Off Valve. If you have performed modifications that have increased boost, horsepower, and overall performance then the PERRIN Blow Off Valve will respond faster than the OEM unit relieve excess pressure. This PERRIN Blow Off Valve cap, piston, and flange feature a CNC machined, 6061 Billet Aluminum construction. The body is CNC machined from a single block of aluminum, and no additional bolt on pieces hinders any potential leaks. The spring of the blow off valve features an adjustable cap which allows you to adjust release pressure settings. If you set it up loose, you will have a smoother release of boost at light loads and RPM. And you can tighten down on the cap if you plan on running higher boost pressures. This feature is independent of relief volume. This means that you can adjust the volume of air released when blowing off. This adjustment is independent of the resistance to blowing off. Venting too little can damage the turbo, while venting too much air can cause less throttle response. In conclusion, the PERRIN Blow Off Valve can be tailored to respond accordingly to your modifications. This blow off valve requires very little maintenance. However when needed, it is simple to disassemble the blow off valve with no special tools required. SHARE THIS