A turbocharger having a variable-nozzle turbine, comprising: a turbine comprising a turbine housing and a turbine wheel mounted therein and connected to a rotatable shaft, the turbine housing defining a chamber surrounding the turbine wheel for receiving exhaust gas from an engine, and an axially extending bore through which exhaust gas is discharged after passing through the turbine wheel, the bore being stepped such that the bore has a first inside diameter for a predetermined distance from an upstream end of the bore axially toward an opposite downstream end of the bore, and the bore then is abruptly reduced to a smaller second inside diameter so as to define a step having an axially upstream-facing step surface; a compressor comprising a compressor housing and a compressor wheel mounted therein and connected to the rotatable shaft; a center housing connected between the compressor housing and the turbine housing; a variable-nozzle assembly comprising an insert having a tubular portion received into the bore of the turbine housing and having a nozzle portion extending generally radially out from one end of the tubular portion, an opposite end of the tubular portion defining an axially downstream-facing end face proximate but spaced from the step surface of the bore, the variable-nozzle assembly further comprising a generally annular nozzle ring axially spaced from the nozzle portion and an array of vanes circumferentially spaced about the nozzle ring and rotatably mounted to the nozzle ring such that the vanes are variable in setting angle for regulating exhaust gas flow to the turbine wheel; and characterized by further comprising; a sealing ring disposed between the end face of the tubular portion of the insert and the step surface of the bore, the sealing ring comprising a generally annular body having a generally U- or V-shaped cross-section oriented such that an open side of the U-or V-shaped cross-section faces in a radial direction, the U- or V-shaped cross-section defining two opposing legs, one of the legs being engaged against the end face of the tubular portion of the insert and the other leg being engaged against the step surface of the bore, wherein the sealing ring is resiliently deformable and is structured and arranged so as to be axially compressed between the end face of the tubular portion of the insert and the step surface of the bore. a turbine comprising a turbine housing and a turbine wheel mounted therein and connected to a rotatable shaft, the turbine housing defining a chamber surrounding the turbine wheel for receiving exhaust gas from an engine, and an axially extending bore through which exhaust gas is discharged after passing through the turbine wheel, the bore being stepped such that the bore has a first inside diameter for a predetermined distance from an upstream end of the bore axially toward an opposite downstream end of the bore, and the bore then is abruptly reduced to a smaller second inside diameter so as to define a step having an axially upstream-facing step surface; a compressor comprising a compressor housing and a compressor wheel mounted therein and connected to the rotatable shaft; a center housing connected between the compressor housing and the turbine housing; a variable-nozzle assembly comprising an insert having a tubular portion received into the bore of the turbine housing and having a nozzle portion extending generally radially out from one end of the tubular portion, an opposite end of the tubular portion defining an axially downstream-facing end face proximate but spaced from the step surface of the bore, the variable-nozzle assembly further comprising a generally annular nozzle ring axially spaced from the nozzle portion and an array of vanes circumferentially spaced about the nozzle ring and rotatably mounted to the nozzle ring such that the vanes are variable in setting angle for regulating exhaust gas flow to the turbine wheel; and characterized by further comprising; a sealing ring disposed between the end face of the tubular portion of the insert and the step surface of the bore, the sealing ring comprising a generally annular body having a generally U- or V-shaped cross-section oriented such that an open side of the U-or V-shaped cross-section faces in a radial direction, the U- or V-shaped cross-section defining two opposing legs, one of the legs being engaged against the end face of the tubular portion of the insert and the other leg being engaged against the step surface of the bore, wherein the sealing ring is resiliently deformable and is structured and arranged so as to be axially compressed between the end face of the tubular portion of the insert and the step surface of the bore.