An internal combustion engine and a method of controlling an internal combustion engine are provided, that are more efficient than existing engines. The internal combustion engine includes a combustion chamber, and the engine is configurable to operate in: a compressionless operating mode where the engine is driven by combustion of fuel and oxidant in the combustion chamber without compression of the fuel and oxidant; and a compression generating operating mode where the engine is used to compress fluid in the combustion chamber.

A method of operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine with a two stage exhaust valve system includes: providing a control rod mechanically coupled to a governor, so that the governor causes a rotation of the control rod. A first stage exhaust valve, a second stage left exhaust valve, and a second stage right exhaust valve are also controllably linked to the control rod; and operating the second stage left exhaust valve and the second stage right exhaust valve by opening at least one of the second stage left exhaust valve and the second stage right exhaust valve before the first stage exhaust valve is completely open in an overlap operation. Related methods and structures for overlap, and/or stagger, and/or limiter operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine are also described.

A method of operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine with a two stage exhaust valve system includes: providing a control rod mechanically coupled to a governor, so that the governor causes a rotation of the control rod. A first stage exhaust valve, a second stage left exhaust valve, and a second stage right exhaust valve are also controllably linked to the control rod; and operating the second stage left exhaust valve and the second stage right exhaust valve by opening at least one of the second stage left exhaust valve and the second stage right exhaust valve before the first stage exhaust valve is completely open in an overlap operation. Related methods and structures for overlap, and/or stagger, and/or limiter operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine are also described.

A closing fork and open spring bias of a center power valve for a hitless control of an adjustable exhaust port 2-stroke motorcycle engine includes a closing fork which includes a flat plate that extends into two substantially parallel flat closing fork arms. An internal closing fork base section cylindrical wall accepts a shaft inserted there through. Each torsion spring of two torsion springs has a first extended leg including an approximately 90-degree bend about where the first extended leg extends out from a spring body of each torsion spring and a second leg extending straight out of a body of each torsion spring. Each of the torsion springs is a mirror of each other where the first extended leg extends from a different side. An upgrade kit and a method to convert a power valve system 2-stroke motorcycle engine to a hitless operation are also described.

An exhaust valve assembly for a two-stroke internal combustion engine has a valve actuator, and a two-part valve having a primary and secondary valves defining first and second decompression passages respectively. The primary valve is operatively connected to the valve actuator. The primary valve is in first, second and third primary valve positions when the valve actuator is in first, second and third actuator positions respectively. The secondary valve is in a first secondary valve position when the valve actuator is in the first or the second actuator position and in a second secondary valve position when the valve actuator is in the third actuator position. The first and second valve decompression passages fluidly communicate with each other when the valve actuator is in the second actuator position, and are fluidly separate from each other when the valve actuator is the first or the third actuator position.

A method of operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine with a two stage exhaust valve system includes: providing a control rod mechanically coupled to a governor, so that the governor causes a rotation of the control rod. A first stage exhaust valve, a second stage left exhaust valve, and a second stage right exhaust valve are also controllably linked to the control rod; and operating the second stage left exhaust valve and the second stage right exhaust valve by opening at least one of the second stage left exhaust valve and the second stage right exhaust valve before the first stage exhaust valve is completely open in an overlap operation. Related methods and structures for overlap, and/or stagger, and/or limiter operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine are also described.

An exhaust valve includes a toroidal surface about an axis of rotation of the valve. The toroidal surface is positionable over a central exhaust port of an engine when lowered. The valve is raised by an actuator in response to increasing rotational speed of the crankshaft of the engine, thereby enlarging and raising the effective opening of the exhaust port. Lateral valve surfaces on either side of the toroidal surface close lateral exhaust ports when the valve is lowered. The lateral valve surfaces may be cylindrical and formed on fins.

Provided is a marine engine, including: a piston; and a compression ratio controller configured to execute lowering processing of moving a top dead center position of the piston toward a bottom dead center side when an engine rotation speed falls within a resonance occurrence range set in advance. A geometrical compression ratio is reduced, and a resonance stress caused by a torsional vibration in a rotary system can thus be suppressed while suppressing a decrease in thermal efficiency compared with a case in which retarding control is applied to a fuel injection timing or a closing timing of an exhaust valve.

Provided is a marine engine, including: an air controller configured to supply compressed air to a combustion chamber in an upstroke of a piston after a crash astern signal is output; a fuel controller configured to stop supply of fuel to the combustion chamber when the crash astern signal is output, and to resume the supply of the fuel after a backward rotation of a crankshaft; and a compression ratio controller configured to move a top dead center position of the piston toward an opposite side of a bottom dead center position of the piston when the crash astern signal is output, and the top dead center position of the piston is on the bottom dead center position side with respect to a predetermined position set in advance.

Provided is a marine engine, including: an air controller configured to supply compressed air to a combustion chamber in an upstroke of a piston after a crash astern signal is output; a fuel controller configured to stop supply of fuel to the combustion chamber when the crash astern signal is output, and to resume the supply of the fuel after a backward rotation of a crankshaft; and a compression ratio controller configured to move a top dead center position of the piston toward an opposite side of a bottom dead center position of the piston when the crash astern signal is output, and the top dead center position of the piston is on the bottom dead center position side with respect to a predetermined position set in advance.