A passive ignition pre-chamber for an internal combustion engine. The pre-chamber is typically implemented as a cap on the electrode end of a spark plug, and encloses a pre-chamber volume in which fuel is mixed with air to form a consistently ignitable mixture. The pre-chamber is passive in the sense that gas exchange with the engine's main combustion chamber is realized by local flow fields near nozzles into the main chamber and by pressure differences between the pre-chamber and the main chamber. The nozzles are sized such that at least one of the nozzles has a larger diameter than the remaining nozzles, as optimized using flow field and pre-chamber turbulence analysis.

A spark-ignited reciprocating piston internal combustion engine includes a pre-chamber ignition system with a housing which is installed in a cylinder head of the spark-ignited reciprocating piston internal combustion engine. An ignition apparatus is disposed in the pre-chamber ignition system and the ignition apparatus protrudes into a cavity in the housing. The cavity is covered by a cover with respect to a combustion chamber of the spark-ignited reciprocating piston internal combustion engine and the cover has at least one aperture which connects the cavity and the combustion chamber to one another in a gas-conducting manner. The housing has a volume and the at least one aperture has a jet cross section and a ratio of the volume to the jet cross section is greater than 100 and less than 300.

To meet both a request to improve the thermal efficiency in the medium load operation of an engine and a request to suppress knocking in the high load and high rotation operation of the engine, the engine includes a main combustion chamber comprising a cylinder block, a cylinder head, and a piston; a pre-chamber having a plurality of injection holes that open into the main combustion chamber; and a spark plug that ignites an air-fuel mixture in the pre-chamber. A compression ratio of the main combustion chamber is not less than 14 and not more than 24. A first index, which is the product between a total cross-sectional area of the plurality of injection holes and the compression ratio, is not less than 0.1496 cm.sup.2 and not more than 0.8449 cm.sup.2.

A method of providing a passive ignition pre-chamber for an internal combustion engine. The pre-chamber is typically implemented as a cap on the electrode end of a spark plug and encloses a pre-chamber volume in which fuel is mixed with air to form a consistently ignitable mixture. The pre-chamber is passive in the sense that gas exchange with the engine's main combustion chamber is realized by local flow fields near nozzles into the main chamber and by pressure differences between the pre-chamber and the main chamber. The nozzles are sized such that at least one of the nozzles has a larger diameter than the remaining nozzles, as optimized using flow field and pre-chamber turbulence analysis.

To effectively suppress strong knock that occurs in the operating region of high load and high rotation in a specific engine having a pre-chamber in a combustion chamber, the engine includes a piston that defines a combustion chamber together with a cylinder block and a cylinder head. The combustion chamber includes a sub-chamber and a main chamber separated from the sub-chamber by a pre-chamber. The specific ratio obtained by dividing a volume of the sub-chamber by a stroke volume of a cylinder is greater than or equal to 0.00005 and less than or equal to 0.00045.

A pre-chamber spark plug for a combustion chamber of an internal combustion engine includes a pre-chamber which has a plurality of openings and which is fluidically connectable to the combustion chamber via the plurality of openings. A fuel/air mixture is introducible from the combustion chamber into the pre-chamber via the plurality of openings. Each of the plurality of openings has a respective flow cross section through which the fuel/air mixture is flowable. With respect to an imaginary plane running along an imaginary axis of the pre-chamber and dividing the pre-chamber into a first half and a second half of equal size, a sum of the flow cross sections of first openings disposed in the first half is greater than a sum of the flow cross-sections of second openings disposed in the second half.

A pre-chamber spark plug has a pre-chamber which has openings, where, with respect to a first plane running in the longitudinal direction of the pre-chamber and dividing the pre-chamber into two halves of equal size, first openings are disposed in a first of the halves and second openings are disposed in a second of the halves. The first openings are spaced apart from a second plane running in the longitudinal direction of the pre-chamber and extending perpendicular to the first plane by a first angle in the circumferential direction of the pre-chamber. The second openings are spaced apart from the second plane by a second angle in the circumferential direction of the pre-chamber. The mean value of the first angles is smaller than the mean value of the second angles.

To meet both a request to improve the thermal efficiency in medium load operation of an engine and a request to suppress knocking in high load operation of the engine, the engine includes a main combustion chamber including a cylinder block, a cylinder head, and a piston; a pre-chamber having a plurality of injection holes that open into the main combustion chamber; and a spark plug that ignites an air-fuel mixture in the pre-chamber. A compression ratio of the main combustion chamber is not less than 14 and not more than 24, an aperture ratio, which is the ratio of a total cross-sectional area of the plurality of injection holes to a volume of the pre-chamber, is not less than 0.0078 mm.sup.−1 and not more than 0.0145 mm.sup.−1, and the volume of the pre-chamber 15 is not less than 0.0430 cm.sup.3 and not more than 0.5631 cm.sup.3.

A combustion pre-chamber device for a spark ignition internal combustion engine is configured to engage a spark plug and be mounted to a cylinder head in communication with a combustion chamber of a cylinder of the engine. The combustion pre-chamber device includes any one or combination of a number of features to improve operating effectiveness, including extending the combustion operating range by improving cooling and optimizing the flow field inside the combustion pre-chamber device.

An engine system employs a pre-assembled and/or removable cartridge. In another aspect, an ignitor, a fuel injector and an air inlet valve are all accessible from a top of a cartridge even after assembly of the cartridge to an engine cylinder head. A further aspect positions centerlines of an ignitor, a fuel injector and an air inlet valve angularly offset from each other and also angularly offset from a vertical centerline of a cartridge to which they are mounted.