One aspect relates to an engine including a working system, having a first piston-cylinder system, comprising a working piston and a working cylinder. The working piston divides the working cylinder into a first working cylinder portion and a second working cylinder portion, a valve system, having a first valve connection and a valve element. The valve system and the working system are connected in a gas conducting manner, the first valve connection can be connected to a negative pressure source, and the valve element is movably arranged in the valve system such that, in a first valve position, the valve element connects the first valve connection to the first working cylinder portion, and, in a second valve position, connects the first valve connection to the second working cylinder portion in a gas conducting manner.