A rotary turbine bypass valve comprises a valve chamber and a valve rotor. The chamber is positioned at a junction of an inlet port, an outlet port and a bypass port. The inlet port is configured to receive exhaust gas, the outlet port is configured to fluidly communicate with a turbine inlet, and the bypass port is configured to fluidly communicate with an exhaust aftertreatment device.
The rotor comprises a first and second recess, the first recess defining a primary flow passage, the second recess defining a secondary flow passage. The rotor is rotatable between a first position in which the rotor substantially blocks exhaust gas flow through the bypass port and a second position in which the rotor permits such. The secondary flow passage is configured to selectively permit fluid communication between the inlet port and the bypass port when the primary flow passage is partially blocked.