Exhaust-gas turbocharger

An exhaust-gas turbocharger (1) comprising:

• a turbine housing (2)
• which has a turbine housing inlet (8) and a turbine housing outlet (9), and
• which has a wastegate duct (10) between the turbine housing inlet (8) and the turbine housing outlet (9), and
• a shut-off element (13) for opening and closing the wastegate duct (10),
• wherein
• the shut-off element (13) comprises a sleeve (14), which is inserted into the turbine housing (2), and a piston (22), which is located in the sleeve (14) so as to be slidingly movable along a longitudinal axis (L) within the sleeve (14) via piston rings (23) between an open position and a closed position,
• the sleeve (14) has a first aperture (15) in communication with the turbine housing inlet (8) and a second aperture (16) in communication with the turbine housing outlet (9), with a gap (20) between the sleeve (14) and turbine housing (2) dimensioned for thermal decoupling of the sleeve (14) and turbine housing (2), and with a sealing ring (21) arranged in the gap (20),
• the piston when in the closed position closes the first aperture (15) and the second aperture (16) to block exhaust flow through the sleeve (14), and when in the open position opens the first aperture (15) and the second aperture (16) for exhaust flow through the sleeve (14), and
• the wastegate duct (10) communicates with the sleeve (14) parallel to the longitudinal axis (L) at the first aperture (15) and transversely with respect to the longitudinal axis (L) at the second aperture (16).