Some embodiments described herein relate to a method of operating a compression ignition (CI) engine. The CI engine can include a combustion chamber. The method of operating the CI engine includes receiving a volume of intake charge in the combustion chamber, compressing the intake charge, injecting a volume of fuel into the combustion chamber, the fuel having a cetane number less than about 40, and combusting substantially all of the volume of fuel. A delay between injecting the volume of fuel into the combustion chamber and initiation of combustion is less than about 2 ms. The CI engine includes at least a two-stroke engine, an opposed-piston engine, a two-stroke opposed piston engine, a five-stroke engine, a six-stroke engine, a free-piston engine, a free piston engine linear, a rotary engine, and/or a Wankel rotary engine.

An internal-combustion engine includes an EGR device that recirculates a portion of exhaust gas, as EGR gas, from an exhaust passage to an intake passage through an EGR valve. A control device for the control device is configured to perform: EGR ratio estimation processing that calculates, by using an estimation model, an estimated EGR ratio; and estimation model update processing that updates the estimation model. The estimation model is configured to calculate the estimated EGR ratio based on a pressure parameter being a ratio of or a difference between gas pressures upstream and downstream of the EGR valve. The pressure parameter is represented by a pressure parameter model that is updatable. The estimation model update processing includes: calculating an actual EGR ratio; and updating the pressure parameter model such that the estimated EGR ratio becomes closer to the actual EGR ratio.

Disclosed is a procedure to minimize NOx during varying engine loads in a 4-stroke diesel engine including at least one cylinder with a cylinder head, first piston on a connecting rod, one actuator mounted on the cylinder head and one of the actuator operated second piston lockable via a hydraulic circuit in various positions in a combustion chamber. The second piston, at the latest during the current compression stroke is actuated by the actuator and locked in the combustion chamber, where it by the first piston introduced air is compressed in a predetermined compression ratio to meet an existing engine load wherein the free operated inlet valve is brought to close the inlet stroke at a piston position where the volume of the combustion air as introduced at the end of the compression stroke gives the predetermined compression ratio and that the injector injects the stated amount of fuel.

Disclosed is a procedure to minimize NOx during varying engine loads in a 4-stroke diesel engine including at least one cylinder with a cylinder head, first piston on a connecting rod, one actuator mounted on the cylinder head and one of the actuator operated second piston lockable via a hydraulic circuit in various positions in a combustion chamber. The second piston, at the latest during the current compression stroke is actuated by the actuator and locked in the combustion chamber, where it by the first piston introduced air is compressed in a predetermined compression ratio to meet an existing engine load wherein the free operated inlet valve is brought to close the inlet stroke at a piston position where the volume of the combustion air as introduced at the end of the compression stroke gives the predetermined compression ratio and that the injector injects the stated amount of fuel.

The compression self-ignition engine fuel injection control device is configured to, during one combustion stroke, perform multiple fuel injections to induce multiple combustions in a cylinder. The fuel injection control device comprises a PCM (70) configured to set an interval between a pre-injection and a main injection in the multiple fuel injections, so as to allow valley regions of a curve indicative of a frequency characteristic of a combustion pressure wave generated by the multiple combustions to fall within respective ranges of a plurality of resonant frequency bands of a structure of an engine body of the engine, wherein the PCM is operable to increase a fuel injection amount of the pre-injection more largely as an engine load becomes lower at the same engine speed.

The compression self-ignition engine fuel injection control device is configured to, during one combustion stroke, perform multiple fuel injections to induce multiple combustions in a cylinder. The fuel injection control device comprises a PCM (70) configured to set an interval between a pre-injection and a main injection in the multiple fuel injections, so as to allow valley regions of a curve indicative of a frequency characteristic of a combustion pressure wave generated by the multiple combustions to fall within respective ranges of a plurality of resonant frequency bands of a structure of an engine body of the engine, wherein the PCM is operable to increase a fuel injection amount of the pre-injection more largely as an engine load becomes lower at the same engine speed.

The compression self-ignition engine fuel injection control device is configured to, during one combustion stroke, perform multiple fuel injections to induce multiple combustions in a cylinder. The fuel injection control device comprises a PCM (70) configured to set an interval between a pre-injection and a main injection in the multiple fuel injections, so as to allow valley regions of a curve indicative of a frequency characteristic of a combustion pressure wave generated by the multiple combustions to fall within respective ranges of a plurality of resonant frequency bands of a structure of an engine body of the engine, wherein the PCM is operable to increase the interval between the pre-injection and the main injection more largely as an engine load becomes lower at a same engine speed.

The compression self-ignition engine fuel injection control device is configured to, during one combustion stroke, perform multiple fuel injections to induce multiple combustions in a cylinder. The fuel injection control device comprises a PCM (70) configured to set an interval between a pre-injection and a main injection in the multiple fuel injections, so as to allow valley regions of a curve indicative of a frequency characteristic of a combustion pressure wave generated by the multiple combustions to fall within respective ranges of a plurality of resonant frequency bands of a structure of an engine body of the engine, wherein the PCM is operable to increase the interval between the pre-injection and the main injection more largely as an engine load becomes lower at a same engine speed.

A system and method for automatically calibrating an engine operating with a first fuel and a second fuel includes comparing each of a plurality of engine operating parameters with a corresponding limit, determining whether any of the plurality of engine operating parameters has exceeded its corresponding limit and, while none of the plurality of engine operating parameters has exceeded its corresponding limit, automatically and incrementally advance start of injection timing.

A system and method for automatically calibrating an engine operating with a first fuel and a second fuel includes comparing each of a plurality of engine operating parameters with a corresponding limit, determining whether any of the plurality of engine operating parameters has exceeded its corresponding limit and, while none of the plurality of engine operating parameters has exceeded its corresponding limit, automatically and incrementally advance start of injection timing.