Abstract: An improved low heat rejection high efficiency engine system for an insulated two stroke internal combustion engine which includes an insulation component provided in association with at least one combustion chamber in order to minimise heat loss during operation, the system having at least one inlet port fluidly connected to a transfer port from a pumping cylinder for inlet of a fresh charge in an induction portion of the operation cycle, the inlet port opened and closed during the operation cycle by an inlet valve, characterized in that the period for which the inlet valve is open during the operation cycle is less than 180° of rotation.

Abstract: This invention provides a method of converting a four-stroke reciprocating piston engine into an efficient two-stroke engine breathing through the original overhead valves. This is achieved by providing a reciprocating positive displacement pump having respective pumping chambers arranged with their outlet adjacent the inlets of the engine and feeding a group of power cylinders. The pump is driven through a step-up drive from the engine and the timing is such that each pumping piston leads alternate ones of the power pistons in the group fed thereby to their respective Top Dead Center positions, the inlet valve to each power cylinder to be fed opens before Bottom Dead Center and closes before TDC, and the outlet valve from the fed power cylinder opens before BDC and closes before TDC.