Abstract: A turbine (22T) of a turbocharger (22) has a housing (24), a turbine wheel (30) disposed within an interior of the housing on a shaft (32) for rotation with the shaft about an axis of rotation (34). A scroll (38) directs a gas toward the axis for imparting rotation to the turbine wheel and shaft. A ring (44) is concentric with the axis and is selectively positionable along the axis for selectively restricting gas directed from the scroll toward the axis. A mechanism (48), including a first-class lever (86) pivotally mounted on the housing, positions the ring along the axis.