Editing Two-stroke engine (section)

{{Short description|Internal combustion engine type}}
{{redirect|2-cycle|the mathematical concept|Cyclic permutation}}
[[File:Two-Stroke Engine.gif|thumb|Animation of a two-stroke engine]]

A '''two-stroke''' (or '''two-stroke cycle''') '''engine''' is a type of [[internal combustion engine]] that completes a [[Thermodynamic power cycle|power cycle]] with two strokes of the [[piston]] (one up and one down movement) in one revolution of the crankshaft in contrast to a [[four-stroke engine]] which requires four strokes of the piston in two crankshaft revolutions to complete a power cycle. During the stroke from bottom dead center to top dead center, the end of the exhaust/intake (or [[Scavenging (automotive)|scavenging]]) is completed along with the compression of the mixture. The second stroke encompasses the combustion of the mixture, the expansion of the burnt mixture and, near bottom dead center, the beginning of the scavenging flows.

Two-stroke engines often have a higher [[power-to-weight ratio]] than a four-stroke engine, since their power stroke occurs twice as often. Two-stroke engines can also have fewer [[moving parts]], and thus be cheaper to manufacture and weigh less.  In countries and regions with stringent emissions regulation, two-stroke engines have been phased out in automotive and motorcycle uses.  In regions where regulations are less stringent, small displacement two-stroke engines remain popular in [[moped]]s and motorcycles.<ref>{{Cite web |title=Docker Maroc |url=https://docker.ma/ |access-date=2023-04-12 |language=fr-FR}}</ref> They are also used in power tools such as [[Chainsaw|chainsaws]] and [[Leaf blower|leaf blowers]]. [[Motor glider#Sustainer motor gliders|SSG and SLG glider planes]] are frequently equipped with two-stroke engines.