Turbocharged Two-stroke Internal Combustion Engine with Four-stroke Capability: 4,907,544

A two-stroke cycle internal combustion engine without crankcase scavenging is disclosed which is able to operate in a four-stroke mode at cranking and idle speeds. The engine utilizes a turbocharger driven by exhaust gases to recharge the cylinder with fresh air or an air/fuel mixture. An auxiliary inlet valve responsive to pressure within the cylinder enables the engine to operate in a four-stroke mode, thus eliminating the need for an externally driven air pump when the engine is either idling, being started, or under light loads where turbocharger boost is too low to supply sufficient flow of air or an air/fuel mixture.