A method for improving combustion in a main combustion chamber of an internal combustion engine and a resulting engine are disclosed. The engine includes a main combustion chamber arranged between a head and a reciprocating piston. A heat retaining element is provided between the head and the main combustion chamber. The heat retaining element is configured to reduce heat transfer from the main combustion chamber into the engine head. A precombustion chamber is provided having a reaction chamber. The reaction chamber is configured to be provided with a secondary charge of air/fuel and a first spark igniter.

An internal combustion engine includes at least one combustion chamber, a main body, at least one purification device, and a cooler. The main body includes therein the at least one combustion chamber, and an exhaust flow path configured to allow exhaust gas flowing out of the at least one combustion chamber to flow down. The at least one purification device is arranged in the exhaust flow path of the main body. The cooler is configured to cool the at least one purification device. Each of the at least one purification device includes a purification member and a case. The purification member is configured to purify the exhaust gas. The case contains the purification member.

Systems, devices, and methods described herein provide one or more radical chemicals generators (RCGs) and/or mini-chambers (M-Cs) that can be used to provide enhanced radical ignition (ERI) in an internal combustion engine. RCGs as described herein can include quenching systems (QSs) that can be configured to quench a flame of combustion products to produce a jet of partial combustion products containing radical species (RS). The jet of partial combustion products can be injected to a main combustion chamber (MCC) of an engine to induce ERI. ERI can proceed under leaner fuel conditions and lower temperatures compared to those needed for conventional thermally induced, fuel oxidation chain initiation reaction processes.