A piston arrangement for an engine is provided and includes a crankshaft located within a crank case and a primary piston located within a first cylinder and interconnected to the crankshaft by a first drive rod for converting reciprocating motion of the primary piston within the first cylinder driven by combustion occurring within the first cylinder into rotational motion of the crankshaft. The arrangement also includes a pumping piston located within a second cylinder and interconnected to the crankshaft by a second drive rod for converting the rotational motion of the crankshaft into reciprocating motion of the pumping piston within the second cylinder. The pumping piston is located between the primary piston and the crank case and seals the first and second cylinders from the crankcase. A stepped-piston and a two-stroke engine are also disclosed.

A uniflow engine includes a cylinder having a cylinder wall, a volume exterior to the cylinder, at least one channel extending between the cylinder wall and the volume, and a valve outside of the cylinder configured to open and close flow communication between the cylinder and the volume through the channel.

A piston arrangement for an engine is provided and includes a crankshaft located within a crank case and a primary piston located within a first cylinder and interconnected to the crankshaft by a first drive rod for converting reciprocating motion of the primary piston within the first cylinder driven by combustion occurring within the first cylinder into rotational motion of the crankshaft. The arrangement also includes a pumping piston located within a second cylinder and interconnected to the crankshaft by a second drive rod for converting the rotational motion of the crankshaft into reciprocating motion of the pumping piston within the second cylinder. The pumping piston is located between the primary piston and the crank case and seals the first and second cylinders from the crankcase. A stepped-piston and a two-stroke engine are also disclosed.

A uniflow engine includes a cylinder having a cylinder wall, a volume exterior to the cylinder, at least one channel extending between the cylinder wall and the volume, and a valve outside of the cylinder configured to open and close flow communication between the cylinder and the volume through the channel.