Differential Stroke-Cycle Piston Technology (D-Cycle)

The D-Cycle piston replaces pistons in traditional internal combustion engines with a split-piston, changing the engine’s basic functionality and transforming the way the engine produces power and adapts to driver demand, improving fuel efficiency by 20%.

The heart of the D-Cycle is a split-piston that completes the four engine strokes in a single crankshaft revolution, reducing the cyclic energy losses. The D-Cycle performs both functions in a single revolution by splitting the piston and using the lightweight top half ­­for the low stress functions of gas exchange and the combined halves for the high stress compression and combustion functions.PistonProgression

The graph above illustrates the working principle of the D-Cycle; the paths of skirt and crown pistons for a typical implementation are shown. The two halves of the D-Cycle piston are mated together during the power stroke, split when the top piston crown performs exhaust and intake strokes, then re-combine again during the compression stroke. Thus, heavy strokes (power and compression) are carried out with both pistons together and light strokes (exhaust and intake) are performed only by the crown piston. The intake stroke volume is reduced to match the desired drive cycle demand with a long Atkinson expansion-to-compression ratio to increase fuel efficiency.

This D-Cycle can be designed into existing production reciprocating engines and in some cases, is practical for retrofit.  The result is a shift in how engines produce power and adapts to duty-cycle loads, improving fuel efficiency. We have been performing R&D on various engines and have successfully retrofitted a range of engine sizes propelled by various fuel types. The adoption of D-Cycle technology can deliver further improvements in vehicle downsizing and weight reduction and is perfectly suited for adoption into the mainstream automotive industry.