Editing Atkinson cycle (section)

==Design==
Atkinson produced three different designs that had a short compression stroke and a longer expansion stroke. The first Atkinson-cycle engine, the ''differential engine'', used opposed pistons. The second and best-known design was the ''cycle engine'', which used an over-center arm to create four piston strokes in one crankshaft revolution. This unusual reciprocating engine had the intake, compression, power, and exhaust [[Stroke (engine)|strokes]] of the [[four-stroke cycle]] in a single turn of the [[crankshaft]], and was designed to avoid infringing certain patents covering [[Otto-cycle]] engines.<ref name=pat367496/> Atkinson's third and final engine, the ''utilite engine'', operated much like a two-stroke engine. 

Apart from the features implemented to avoid Otto patents, the truly unique Atkinson's design is that the engines have an expansion stroke that is longer than the compression stroke, and by this method the engine achieves greater [[thermal efficiency]] than a traditional piston engine. Atkinson's engines were produced by the British Gas Engine Company and also licensed to other overseas manufacturers. 

Many modern engines now use a crankshaft center-line offset from the cylinder center-line (making them [[Desaxe]] engines) and/or unconventional valve timing to produce the effect of a shorter compression stroke/longer power stroke. Miller applied this technique to the four-stroke engine, so it is sometimes referred as the Atkinson/[[Miller cycle]], US patent 2817322 dated Dec 24, 1957.<ref>{{US patent|2817322}}</ref> In 1888, Charon filed a French patent and displayed an engine at the Paris Exhibition in 1889. The Charon gas engine (four-stroke) used a similar cycle to Miller, but without a supercharger. It is referred to as the "Charon cycle".<ref>{{cite book |url={{Google books|8d03AAAAMAAJ|page=152|keywords=charon |plainurl=yes}} |title=A text-book on gas, oil and air engines: or, Internal combustion motors without boiler |page=152 |first=Brian |last=Donkin |publisher=C. Griffin and company, limited |year=1896}}</ref>

[[Hugo Güldner]] argued in his 1914 book that Körting was the first firm to build a gas engine with a short compression stroke and a longer expansion phase in 1891, based on a design first proposed by [[Otto Köhler (engineer)|Otto Köhler]] in 1887. This engine also had an engine-load dependent valve train which increased the intake and compression stroke with increasing engine load. On the other hand, the compression was decreasing at low and medium loads, which ultimately reduced the efficiency.<ref>{{cite book |last=Güldner |first=Hugo |title=Das Entwerfen und Berechnen der Verbrennungskraftmaschinen und Kraftgas-Anlagen |trans-title=The design and calculation of internal combustion engines and power gas systems |publisher=Springer-Verlag |publication-place=Berlin, Heidelberg |year=1914 |isbn=978-3-662-24387-9 |doi=10.1007/978-3-662-26508-6 |page=64}}</ref>

[[Roy Fedden]], at [[Bristol]], tested an arrangement in the [[Bristol Jupiter]] IV engine in 1928, with variable retard timing allowing part of the charge to be blown back into the intake manifold, in order to have sustainable reduced operation pressures during takeoff.{{cn|date=June 2021}}

Modern engine designers are realizing the potential fuel-efficiency improvements the Atkinson-type cycle can provide.<ref>{{cite web |url=http://www.autos.ca/auto-tech/auto-tech-atkinson-cycle-engines-and-hybrids/ |title=Auto Tech: Atkinson Cycle engines and Hybrids |work=Autos.ca |date=2010-07-14 |access-date=2013-02-23}}</ref>