Pressure intensifier device for increasing pressure in a pressurized fluid chamber of a piston/cylinder unit, preferably of a casting piston/casting cylinder unit of a die casting machine, comprising - a pressure intensifier cylinder and a pressure intensifier piston, which is guided in an axially movable manner in the cylinder, wherein - the pressure intensifier cylinder comprises an outlet region, an inlet region upstream of the outlet region, and a piston guiding chamber having a pressure intensifier piston chamber, into which a pressure intensifier inlet line opens, and/or a pressure intensifier backpressure chamber, into which a pressure intensifier backpressure line opens, - the pressure intensifier piston comprises a piston part, which is guided in the piston guiding chamber, and a piston rod, which extends from the piston part to the inlet region, in a retracted release position releases a fluid connection between the inlet region and the outlet region and, in an advanced blocking position, blocks this connection with a free end portion, with which it extends into the outlet region, and, - over a portion that can be passed through by the free end portion of the piston rod during movement from the release position into the blocking position, the outlet region comprises a free passage cross section for the free piston rod end portion that is at least equal in size to a rod cross section of the free piston rod end portion, - a pressure intensifier inlet valve, which is controlled independently of a pressure in the pressurized fluid chamber of the piston/cylinder unit, is arranged in the pressure intensifier inlet line, and/or - a pressure intensifier backpressure valve, which is controlled independently of a pressure in the pressurized fluid chamber of the piston/cylinder unit, is arranged in the pressure intensifier backpressure line, and/or - the outlet region is designed as a portion of the pressure intensifier cylinder which is narrowed radially relative to the inlet region, wherein a diameter of the outlet region is greater than a diameter of the free piston rod end portion in order to form an intermediate open or sealed annular gap between the free piston rod end portion, in the blocking position thereof, and a circumferential rim of the outlet region, and/or wherein a circumferential rim of the cylindrical portion of the outlet region has an insertion cone on the inlet side, characterized in that the outlet region is embodied without a check valve. - a pressure intensifier cylinder and a pressure intensifier piston, which is guided in an axially movable manner in the cylinder, wherein - the pressure intensifier cylinder comprises an outlet region, an inlet region upstream of the outlet region, and a piston guiding chamber having a pressure intensifier piston chamber, into which a pressure intensifier inlet line opens, and/or a pressure intensifier backpressure chamber, into which a pressure intensifier backpressure line opens, - the pressure intensifier piston comprises a piston part, which is guided in the piston guiding chamber, and a piston rod, which extends from the piston part to the inlet region, in a retracted release position releases a fluid connection between the inlet region and the outlet region and, in an advanced blocking position, blocks this connection with a free end portion, with which it extends into the outlet region, and, - over a portion that can be passed through by the free end portion of the piston rod during movement from the release position into the blocking position, the outlet region comprises a free passage cross section for the free piston rod end portion that is at least equal in size to a rod cross section of the free piston rod end portion, - a pressure intensifier inlet valve, which is controlled independently of a pressure in the pressurized fluid chamber of the piston/cylinder unit, is arranged in the pressure intensifier inlet line, and/or - a pressure intensifier backpressure valve, which is controlled independently of a pressure in the pressurized fluid chamber of the piston/cylinder unit, is arranged in the pressure intensifier backpressure line, and/or - the outlet region is designed as a portion of the pressure intensifier cylinder which is narrowed radially relative to the inlet region, wherein a diameter of the outlet region is greater than a diameter of the free piston rod end portion in order to form an intermediate open or sealed annular gap between the free piston rod end portion, in the blocking position thereof, and a circumferential rim of the outlet region, and/or wherein a circumferential rim of the cylindrical portion of the outlet region has an insertion cone on the inlet side,