Abstract: The auxiliary combustion chamber of a four-cycle stratified-charge piston engine is divided into a primary cavity and a secondary cavity both formed in an insert liner received in the cylinder head. The primary cavity receives a relatively rich mixture which passes into the secondary cavity, and the main combustion chamber receives a relatively lean mixture. A spark plug communicates with the primary cavity. A long torch passage connects the primary cavity with the central portion of the main combustion chamber, and one or more short torch passages connect the secondary cavity with a peripheral portion of the main combustion chamber. The purpose is to reduce emission of NO.sub.x without adversely affecting emissions of CO and HC, and to improve fuel economy.

Abstract: Exhaust gas from an internal combustion piston engine is recirculated through a rich mixture auxiliary intake passage leading to an auxiliary combustion chamber. A valve controls the relative proportions of exhaust gas and air supplied to the auxiliary intake passage, and the valve is controlled by means responsive to suction pressure downstream from the auxiliary throttle valve, and is also responsive to movement of that throttle valve.

Abstract: A residual gas control apparatus for internal combustion engines of the type including a main combustion chamber connected through a torch passage to an auxiliary combustion chamber having a spark plug, the residual gas control including a partial partition dividing the auxiliary combustion chamber into a first zone exposed to the spark plug and a second zone exposed to the torch passage, there being openings connecting the two zones, the partition and openings serving to control the percentages of residual gas in the two zones so as to produce optimum ignition and reduce NOx generation, and also to minimize turbulence in the vicinity of the spark plug.

Abstract: An internal combustion piston engine employs a stratified charge. Separate carburetor throats are provided for directing rich air-fuel mixture to a prechamber and lean air-fuel mixture to a main combustion chamber. The rich mixture is heated by the engine exhaust gases and then delivered to the prechamber. A spark plug ignites the rich mixture and causes a torch flame to project laterally through a torch slot in the prechamber wall into the main combustion chamber to ignite the lean mixture contained therein. In this way, the amount of unwanted emissions such as carbon monoxide may be reduced in the exhaust gases discharged into the atmosphere.

Abstract: A three-valve stratified-charge internal combustion piston engine has an auxiliary combustion chamber connected to each main combustion chamber through a torch nozzle. A rich mixture is supplied to the auxiliary chamber and a lean mixture is supplied to the main chamber. A portion of the exhaust gases from the main chamber is recirculated through a control valve to mix with the rich mixture supplied to the auxiliary chamber. For loaded conditions of the engine, additional exhaust gases from the main chamber are recirculated through a control valve to mix with the lean mixture supplied to the main chamber. The control valves are automatically operated by means responsive to engine operating conditions.

Abstract: Reduction of NO.sub.x emissions from a four-cycle stratified charge internal combustion piston engine is accomplished by (a) spark ignition of a rich mixture in a first chamber containing residual exhaust gas, followed by (b) torch ignition of rich mixture in a second chamber under turbulent conditions, causing (c) torch ignition of a stratified charge in a lean mixture in the main combustion chamber. The result is a reduction in peak temperature in the combustion process, with consequent reduction in NO.sub.x emissions in the engine exhaust gases. Exhaust gas is not recirculated. Said first chamber, which contains residual gas from the previous combustion cycle, contains the spark gap between spark plug electrodes and the spark gap is located near a restricted connection between the first and second chambers and remote from a closed end of the first chamber. Means are provided for changing the volume of said first chamber while the engine is operating, in accordance with variations in load on the engine.