Systems and methods for extra-stroke engine cycle operation

A controller configured for operating an engine in an extra-stroke mode, the controller comprising:

• a processor;
• and
• a memory storing instructions that, when executed by the processor, cause the controller to generate commands for operations including:
• transitioning operation of the engine from a four-stroke mode to the extra-stroke mode or from the extra-stroke mode to the four-stroke mode,
• wherein the four-stroke mode includes an intake stroke, a compression stroke, a power stroke, and an exhaust stroke, and
• wherein the extra-stroke mode includes at least six strokes of a piston disposed within a combustion chamber of an engine cylinder of the engine, during which an exhaust valve of the engine cylinder is opened only once during the at least six strokes, during or immediately preceding a final upward stroke of the at least six strokes, and during which an intake valve of the engine cylinder is opened only once during the at least six strokes, during or immediately preceding an initial downward stroke.

An engine system, comprising:

• an engine cylinder;
• a piston disposed within a combustion chamber of the engine cylinder;
• a fuel injector configured to inject fuel for combustion in the engine cylinder;
• and
• a controller operative to generate commands that cause the engine system to:
• during a first downward stroke of the piston, open an intake valve of the engine cylinder to allow a mass of air to enter the combustion chamber;
• during a first upward stroke of the piston immediately subsequent to the first downward stroke, compress the mass of air within the combustion chamber;
• during a second downward stroke of the piston immediately subsequent to the first upward stroke, decompress the mass of air within the combustion chamber before fuel is injected into the combustion chamber;
• during a second upward stroke of the piston immediately subsequent to the second downward stroke, recompress the mass of air within the combustion chamber without opening an exhaust valve of the engine cylinder;
• during, or immediately preceding, a subsequent downward stroke of the piston, inject a mass of fuel into the combustion chamber to form an air-fuel mixture within the combustion chamber and ignite the air-fuel mixture within the combustion chamber;
• and
• during a subsequent upward stroke of the piston immediately subsequent to the subsequent downward stroke of the piston, open the exhaust valve of the engine cylinder to allow exhaust to exit the engine cylinder.