Turbocharger with turbine nozzle vanes and an annular rotary bypass valve

A turbocharger (20) includes an annular bypass volute (60) to allow exhaust gas to bypass the turbine wheel (54). An annular bypass valve (70) is disposed in the bypass volute (60). The bypass valve comprises a fixed annular valve seat (72) and a rotary annular valve member (74) arranged coaxially with the valve seat. The valve member is disposed against the valve seat and is rotatable about the axis for selectively varying a degree of alignment between respective orifices (73) in the valve seat and valve member. The valve member is rotatably driven by a rotary actuator (80) and drive linkage that rotates about an axis parallel to and offset from the axis about which the valve member rotates.