1The BOV is a pressure relief device on the intake tract to prevent the turbo's compressor from going into surge. 2The valve can use a combination of manifold pressure signal and spring force to detect when the throttle is closed. 3When the throttle is closed rapidly, the BOV vents boost in the intake tract to atmosphere to relieve the pressure and eliminate surge. 4With 8 discharge ports that draw in surrounding air and release an aggressive JDM racing discharge sound. 5The turbo BOV has dual spring system to promote response and hold up to 30 PSI boost pressure. 6The blow off valve is with 2 bolt mounting design and 40mm hardanodized valve for increased airflow. Item Type: Blow Off Valve Material:Aluminium OEM:SDD-BOVGRSBL, FPG250 Size ofFlangePipe: Approx.2.5in/6.4cm Application: For TYPE-SDump Pipe Flange For TYPE-RS Dump Pipe Flange When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations.Surge can eventually lead to thrust bearing failure due to the high loads associated with it. Thevalvecanuseacombinationofmanifoldpressuresignalandspringforcetodetectwhenthethrottleisclosed. Whenthethrottleisclosedrapidly,theBOVventsboostintheintaketracttoatmospheretorelievethepressureandeliminatesurge. 1 x Turbine Valve 1 x Hose 1 x Flange Pipe 1 x Flange Pipe Interface 1 x Gasket 4 x Clamp 2 x Nut 2 x Screw 2 x Bracket 1. Please double check the part number of your item, matching information is for reference only.2. If you are unsure of the item, please contact us before buying to avoid unnecessary return, thanks