HKS Standard and Racing Bypass valves are push-type valves that utilize calibrated spring rate and vacuum line pressure to remain closed against the pressurized air in the charge pipe. As the throttle plate closes, vacuum is created in the line and combined with the force of the pressurized air in the charge pipe, the blow off valve pushes open and allows pressurized air to escape.

HKS Racing Bypass Valves function like the Standard Bypass Valves, but incorporate an additional pressurized port to insure valve closure under extreme high boost levels. The Racing Bypass Valves can also be used as a safety "pop-off" valve if the second port is connected to a pressure source that does not see vacuum. For added flexibility and function, HKS Racing Bypass Valves are offered in various adjustable boost pressure ranges that are determined by a specific spring rate.