Editing Two-stroke engine (section)

===Stepped piston engine===
The piston of this engine is "top-hat"-shaped; the upper section forms the regular cylinder, and the lower section performs a scavenging function. The units run in pairs, with the lower half of one piston charging an adjacent combustion chamber.

The upper section of the piston still relies on total-loss lubrication, but the other engine parts are sump lubricated with cleanliness and reliability benefits. The mass of the piston is only about 20% more than a loop-scavenged engine's piston because skirt thicknesses can be less.<ref>{{cite web | url=https://1library.net/article/stepped-piston-engines-basic-design-parameters-engine-geometry.qvvx8ngq | title=Stepped-Piston Engines - BASIC DESIGN PARAMETERS 3.1 Engine and Port Geometry }}</ref>