The new 2&2-stroke cycle engine completes 4 strokes in every revolution by a 2-part piston - the piston cap and piston body. The light piston cap performs the exhaust/intake strokes separately through a light operating mechanism and the heavy compression/ combustion strokes jointly with the piston body. Furthermore the 2&2-cycle allows differential strokes in displacements and periods.
Completing the 4 strokes the 2&2-cycle inherits from the 4-cycle the exhaust characteristics that are amiable to current emission treatments. Yet having a combustion in every revolution the 2&2-cycle produces torque like a 2-cycle. Developing the 2&2-cycle is cost-effective as it shares the same know-how and most hardware with the popular 4-cycle.
This article describes the 2&2-cycle technology and its promises and challenges.