Patented in 1882, the Atkinson four-stroke design relies on variable stroke lengths to boost efficiency and power over the traditional Otto engine. The design utilizes a shorter, more efficient compression stroke, while allowing combustion to act on the piston longer via a physically longer power stroke. This is made possible via the use of multi-link connecting rods, making for a far more efficient thermodynamic cycle within the piston and flywheel portion of the engine block. | EngineLabs

Check out the Atkinson cycle. Where the compression and combustion cycles have different stroke lengths in the bore. | EngineLabs