The HKS Super Sequential Blow-Off Valve (SSQV) for the 08-09 EVO X is a dual stage pull-type relief valve. Unlike typical push type blow-off valves, the SSQV will not leak under any level of boost because the boost pressure keeps the valve closed against its seat. The SSQV releases excess boost when there is a pressure alteration. This ensures a quick valve response and complete closure during idle. Many competitors use a push-type blow-off valve design with a large valve to accommodate high boost / high horsepower applications. These large valves react slowly and require high pressure to open, and are not able to activate and prevent compressor surge at light-load conditions.
On the other hand, smaller, fast reacting push-type valves do not discharge the airflow capacity required for high horsepower applications and tend to slowly open and leak as boost pressure overpowers the spring. For maximum performance, the HKS SSQV incorporates both a small primary valve for ultra quick activation, and a larger secondary valve for additional discharge capacity. The SSQV is engineered to initially open the small primary valve at light throttle and load conditions, then sequentially opens the secondary valve for additional relief capacity under high boost and load conditions.