as is well known in the supercharger art the bypass valve 53 is normally closed when the supercharger 15 is operating to transfer volumes of air from the inlet 19 to the outlet 23 however when reduced levels of boost are sufficient the bypass valve 53 can be moved somewhat from its closed position as shown in fig1 in which no air can flow from the outlet back into the inlet toward an open position in which an increasing amount of air is communicated from the outlet 23 back into the supercharger inlet 19 one result of moving the bypass valve 53 toward a more open position is that the boost pressure of the air in the air duct 29 is somewhat reduced from the normal boost pressure present when the bypass valve 53 is fully closed however one difference in the bypass valve required for use in a superturbo boost system is that the overall air flow capacity flow area of the bypass valve 53 shown herein must be larger than the bypass valve which would be used in a typical basic supercharger system as the vehicle engine reaches relatively higher engine speeds the clutch 27 will be disengaged so that the supercharger 15 is not being driven but at the same time the turbocharger 33 is being driven by the flow of exhaust gas in the duct 37 during this mode of operation the bypass valve 53 is in the fully opened position and must be large enough not to present any undesirable flow restriction to the air which flows from the intake 11 through the air duct 29 and through the compressor 31 the exhaust.