Patent ID: 8046997

Claim:
A supercharged engine comprising: an intake manifold; a screw compressor type supercharger connected to the intake manifold and comprising: a supercharger housing; a forward end of the supercharger housing; a rearward end of the supercharger housing; a throttle body in fluid communication with the rearward end; a compressed air passage between the forward end and the rearward end and in fluid communication with the intake manifold; a first screw rotatably residing in the supercharger housing; a second screw rotatably residing in the supercharger housing and cooperating with the first screw to draw air into the housing through the rearward end and to pump compressed air out of the housing and into the intake manifold through the compressed air passage; a bypass passage connecting the compressed air passage to the rearward end; a bypass valve controlling the passage of the compressed air through the bypass passage from the compressed air passage to the rearward end; a bypass valve diaphragm having an engine vacuum port in fluid communication with engine intake Manifold Absolute Pressure (MAP) and connected to the bypass valve for opening and closing the bypass valve, the diaphragm moving the bypass valve toward a fully open position for low MAP and toward a fully closed position for high MAP; and a bypass valve spring biasing the bypass valve towards the fully open position, wherein a combination of the diaphragm and the bypass valve spring combine to position the bypass valve in the fully open position for engine MAP less than approximately 14.7 PSIA.