When the geometric compression ratio of an engine body is set to 13:1 or more and the engine body operates in a preset high load region, the effective compression ratio of the engine body is set to 12:1 or more with a difference from the geometric compression ratio being within 2, a gas to be introduced into a combustion chamber is supercharged by a supercharging system, fuel is injected at least in a compression stroke by an injector, and after the fuel injection is finished, an air-fuel mixture in the combustion chamber is ignited by an ignition device before the compression top dead center and is thus burned by flame propagation in the engine body, and then the unburned air-fuel mixture is burned by compression ignition.

A control device for a compression ignition engine is provided, which causes an injector to perform a pre-injection and a main injection, sets fuel injection timings of these injections so that an interval between a first peak of a heat release rate resulting from the combustion of fuel injected by the pre-injection and a second peak of the heat release rate resulting from the combustion of fuel injected by the main injection becomes an interval to make pressure waves caused by these combustions cancel each other out, and when an increase of a wall surface temperature of a combustion chamber is detected, controls the injector to reduce the injection amount and retard the injection timing of the pre-injection compared with a case where the temperature increase is not detected, under a condition that engine load and speed are the same.

An engine combustion control method may include: determining, by a controller, whether a fuel injection timing of an engine matches with an engine running condition of the engine; performing, by the controller, when the fuel injection timing matches with the engine running condition of the engine, a fuel injection variable establishment control (or a variable control of a fuel injection timing) that performs a Wavelet process on a frequency band selected by matching a vibration frequency of a vibration sensor signal to an engine frequency transformed under an engine running condition; and when the fuel injection timing matches with the engine running condition, updating a fuel injection parameter by correcting a target value of a combustion factor based on the fuel injection timing.

A method of controlling a dual fuel engine system includes adjusting a phasing control parameter such as air-fuel ratio (AFR), based on a phasing signal to limit an error in a phasing of combustion of gaseous fuel. The cylinder is switched to a dual fuel liquid pilot-ignited mode by commanding direct injection of an early pilot shot of liquid fuel, based on the adjustment to the phasing control parameter, and production of a spark to ignite gaseous fuel in the cylinder. Switching the cylinder to the dual fuel liquid pilot-ignited mode is completed by commanding direct injection of an early pilot shot and a second pilot shot of liquid fuel to ignite gaseous fuel in response to combustion of the early and second pilot shots in the cylinder.

Various methods and systems are provided for diagnosing a condition of a fuel injector of an engine. In one example, a method for an engine includes injecting a first pulse of fuel as a first pilot injection into a first subset of cylinders of a plurality of engine cylinders, where the first pilot injection precedes a primary injection of fuel into the first subset of cylinders by a duration; correlating a first response in an engine operating parameter to the first pilot injection; and adjusting the primary injection of fuel into the first subset of cylinders based on the first response. In one example, the first pilot injection precedes the primary injection by a predefined short duration and the primary injection of fuel is adjusted within a predefined or preset upper limit and lower limit.

A fuel injection control system for a diesel engine is configured to, during one combustion cycle, perform multiple fuel injections to induce multiple combustions in a cylinder. The fuel injection control system comprises a PCM for controlling a fuel injection of the diesel engine. The PCM is configured to execute control for: at a first timing during compression stroke, injecting fuel in a first amount; at a second timing after the first timing and during the compression stroke, injecting fuel in a second amount greater than the first amount; and, at a third timing after the second timing and approximately a top dead center of the compression stroke, injecting fuel in a maximum amount greater than the first and second amounts.

A fuel injection control system for a diesel engine configured to perform multiple fuel injections to induce multiple combustions. A PCM is configured to, during compression stroke, perform a main injection and multiple pre-stage injections prior to the main injection, and to cause a ratio of a maximum injection amount of the multiple pre-stage injections to an injection amount of the main injection to become smaller when the load of the diesel engine is less than a given load than when the load of the diesel engine is greater than the given load, and cause an injection interval between the main injection and one of the multiple pre-stage injections immediately preceding the main injection to become smaller when the load of the diesel engine is less than the given load than when the load of the diesel engine is greater than the given load.

A method and a system for controlling combustion of a natural gas engine. The method includes: determining, based on a current operation parameter of a natural gas engine, an operation state of the natural gas engine, and calculating a total injection quantity of natural gas and pilot diesel required by the natural gas engine in the operation state; adopting a direct injection diffusion-combustion mode in a case that the operation state is an idle state or a low load state; adopting a natural gas homogeneous hybrid active control compression-ignition mode in a case that the operation state is a medium load state; configuring the total injection quantity into three parts including a compression-ignition natural gas injection quantity, a pilot diesel injection quantity, and a diffusion-combustion natural gas injection quantity in a case that the operation state is a high load state, and sequentially injecting them into a combustion chamber.

Methods and systems are disclosed for operating an engine that includes fuel injectors that supply fuel to cylinders of the engine. According to the methods and system, variation of individual fuel injection amounts injected by a sole fuel injector are determined so that it may be determined if individual fuel injector variation may be contributing to engine air-fuel ratio variation.

A combustion control system for a dual fuel engine includes a combustion control unit structured to receive phasing data for combustion of a main charge of gaseous fuel ignited by way of pilot shots of a liquid fuel, output a pilot fueling command based on the phasing data, and output a valve timing command. The combustion control unit is further structured to vary a phasing of combustion of a main charge of a gaseous fuel ignited by pilot shots of a liquid fuel based on an adjustment to at least one of a pilot shot delivery parameter or a valve timing parameter such as intake valve closing timing from a first engine cycle to a second engine cycle. Control of the intake valve timing can be based on a main pilot shot timing error.