The new HKS SSQV style BOV uses a unique sequential valve structure and a differential pressure control system, which allows for a broad operation range from low boost to high boost.This Blow-Off Valve is a dual stage pull-type relief valve. Unlike typical push type blow-off valves, it will not leak under any level of boost because the boost pressure in chamber keeps the valve closed against its seat. It releases excess boost when there is a pressure alteration in chambers, not by the rate of boost pressure or vacuum in the line.