Complex sentence: Two-stage refers to the use of two impellerson a common driveshaft, constituting two superchargers in series; as air was drawn through the air intake fuel was pumped into the airstream by the carburettor.
Split into simpler sentences: Two-stage refers to the use of two impellers on a common driveshaft, constituting two superchargers in series. As air was drawn through the air intake, fuel was pumped into the airstream by the carburettor.