US Patent 7270108 Opposed piston, homogeneous charge pilot ignition engine

An engine of the opposed piston, two-stroke, compression ignition type includes provision for injection of a main charge of liquid fuel into the bore of a cylinder between opposed pistons early in a compression stroke to permit the fuel to evaporate and mix with air during the remainder of the compression stroke to the point where the stoichiometric components of the mixture are insufficient for autoignition. Further provision is made for injection of a pilot charge of liquid fuel into the compressed air/fuel mixture later in the compression stroke. The pilot charge provides a stoichiometric component which autoignites, thereby activating ignition of the compressed air/fuel mixture.