A piston engine is provided; the piston engine has a cylinder, a main piston and an auxiliary piston, a combustion chamber is formed between the main piston and the auxiliary piston within the cylinder, the auxiliary piston moves in different frequency along it centerline, a plateau is formed near TDC position of the combustion chamber volume V, there is a preferable PPP in each configuration of the piston, when the combustion peak pressure is at the position of preferable PPP position, the best torque is achieved. Different piston configurations, different ignition timings, dynamic energy recovery and storage are also provided in the invention.

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: 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.

A method for starting a compression ignition engine having at least one cylinder with a reciprocating piston located therein, an intake valve configured to control the intake of air to an intake port of the cylinder and an exhaust valve configured to control the expulsion of gas from an exhaust port of the cylinder. The method includes the steps of: cranking the engine, conditioning intake air at the intake port of the cylinder to raise the temperature of air in the cylinder, controlling a valve timing the intake valve and/or the exhaust valve to allow the piston to compress the air within the cylinder, thereby increasing the temperature of the air within the cylinder, and injecting fuel into the cylinder when the air within the cylinder has been heated to a temperature sufficient to support compression ignition of a gasoline and air mixture within the cylinder.

A method for starting a compression ignition engine having at least one cylinder with a reciprocating piston located therein, an intake valve configured to control the intake of air to an intake port of the cylinder and an exhaust valve configured to control the expulsion of gas from an exhaust port of the cylinder. The method includes the steps of: cranking the engine, conditioning intake air at the intake port of the cylinder to raise the temperature of air in the cylinder, controlling a valve timing the intake valve and/or the exhaust valve to allow the piston to compress the air within the cylinder, thereby increasing the temperature of the air within the cylinder, and injecting fuel into the cylinder when the air within the cylinder has been heated to a temperature sufficient to support compression ignition of a gasoline and air mixture within the cylinder.

Provided is a control device for an internal combustion engine capable of estimating a compression ratio of the internal combustion engine at the time of fuel cut of the internal combustion engine and without being affected by an intake air amount and an intake air temperature. A compression ratio ε is calculated on the basis of a change of in-cylinder pressure P with respect to crank angle θ at timing when an in-cylinder volume change rate dV/dθ/V takes an extreme value or at timing from closing of an intake valve 109 to the start of ignition of the air-fuel mixture in the cylinder.

A control method for internal combustion engine with a fuel injection valve configured to directly inject fuel into a cylinder and an ignition plug configured to directly spark-ignite the fuel injected from the fuel injection valve includes comparing an actual behavior, which is an actual changing behavior of an engine revolution speed at an engine start, to a reference behavior set in advance, and switching from stratified combustion in which a fuel spray injected from the fuel injection valve and staying around the ignition plug is directly spark-ignited to homogeneous combustion in which a homogeneous air-fuel mixture is formed in a combustion chamber and the fuel is burned and increasing a mechanical compression ratio of the internal combustion engine as compared to the case where the actual behavior and the reference behavior match if the actual behavior is different from the reference behavior.

A control method for internal combustion engine with a fuel injection valve configured to directly inject fuel into a cylinder and an ignition plug configured to directly spark-ignite the fuel injected from the fuel injection valve includes comparing an actual behavior, which is an actual changing behavior of an engine revolution speed at an engine start, to a reference behavior set in advance, and switching from stratified combustion in which a fuel spray injected from the fuel injection valve and staying around the ignition plug is directly spark-ignited to homogeneous combustion in which a homogeneous air-fuel mixture is formed in a combustion chamber and the fuel is burned and increasing a mechanical compression ratio of the internal combustion engine as compared to the case where the actual behavior and the reference behavior match if the actual behavior is different from the reference behavior.

The present disclosure relates to piston engine systems which are no longer restricted by their compression ratios. Rather, a mixture of fuel and pre-compressed air is used to complete the combustion. The pressure of the compressed air is independently controlled. As a result, the clearance volume can be reduced to less than 1/50 or to zero, and the piston engine systems can be used with different types of fuels, for example, gasoline, diesel, ethanol, or vegetable oils.

Methods and systems are provided for an engine configured to deactivate at least some cylinders. In one example, an engine system may comprise a first group of cylinders having a first compression ratio and a second group of cylinders having a second compression ratio greater than the first.