Abstract: A turbocharger can include a center housing; a bearing disposed in a through bore of the center housing where the through bore of the center housing defines a longitudinal axis; a shaft rotatably supported by the bearing; a compressor wheel operatively coupled to the shaft; a turbine wheel operatively coupled to the shaft; and a turbine housing assembly operatively coupled to the center housing where the turbine housing assembly includes: a turbine housing; and a cartridge that includes a nozzle wall component and a plate component that are spaced axially by spacers, where the nozzle wall component includes spacer bores for the spacers and where the nozzle wall component has a non-circular outer perimeter defined at least in part by arcs where adjacent arcs intersect at intersection points, and where each of the intersection points is radially outwardly from a respective one of the spacer bores.

Abstract: A turbocharger includes a variable-nozzle turbine having a variable vane assembly formed as a cartridge. A pipe-shaped insert of the cartridge fits into an axial bore in the turbine housing. The variable vane assembly includes a nozzle ring to which the variable vanes are mounted. A composite heat shroud is disposed between and axially compressed between the turbocharger's center housing and the nozzle ring. The heat shroud is constructed such that heating of the shroud causes the shroud to deform so as to increase the axial preload exerted by the shroud. In one embodiment the heat shroud is a two-layer structure in which the two layers are formed of different materials having different coefficients of thermal expansion.