Editing Four-stroke engine (section)

== History ==

=== Otto cycle ===
{{main|Otto cycle}}
{{see also|Otto engine}}
[[File:PSM V18 D500 An american internal combustion otto engine.jpg|thumb|left|An Otto Engine from 1880s US Manufacture]]

[[Nicolaus Otto|Nikolaus August Otto]] was a traveling salesman for a grocery concern. In his travels, he encountered the internal combustion engine built in Paris by Belgian expatriate [[Étienne Lenoir|Jean Joseph Etienne Lenoir]].  In 1860, Lenoir successfully created a double-acting engine that ran on illuminating gas at 4% efficiency. The 18&nbsp;litre [[Étienne Lenoir#Lenoir engine|Lenoir Engine]] produced only 2&nbsp;horsepower. The Lenoir engine ran on illuminating gas made from coal, which had been developed in Paris by [[Philippe le Bon|Philip Lebon]].<ref name="NAMuseum">{{cite web |url=http://www.nicolaus-august-otto.de/node/15 |title=125 Jahre Viertaktmotor |trans-title=125 Years of the Four Stroke Engine |website=Oldtimer Club Nicolaus August Otto e.V. |location=Germany |language=de |url-status=dead |year=2009 |archive-url=https://web.archive.org/web/20110507083259/http://www.nicolaus-august-otto.de/node/15 |archive-date=2011-05-07}}</ref>

In testing a replica of the Lenoir engine in 1861, Otto became aware of the effects of compression on the fuel charge. In 1862, Otto attempted to produce an engine to improve on the poor efficiency and reliability of the Lenoir engine. He tried to create an engine that would compress the fuel mixture prior to ignition, but failed as that engine would run no more than a few minutes prior to its destruction. Many other engineers were trying to solve the problem, with no success.<ref name="NAMuseum" />

In 1864, Otto and [[Eugen Langen]] founded the first internal combustion engine production company, NA Otto and Cie (NA Otto and Company). Otto and Cie succeeded in creating a successful atmospheric engine that same year.<ref name="NAMuseum" />
The factory ran out of space and was moved to the town of [[Deutz, Cologne|Deutz]], Germany in 1869, where the company was renamed to [[Deutz AG|Deutz Gasmotorenfabrik AG]] (The Deutz Gas Engine Manufacturing Company).<ref name="NAMuseum" /> In 1872, [[Gottlieb Daimler]] was technical director and [[Wilhelm Maybach]] was the head of engine design. Daimler was a gunsmith who had worked on the Lenoir engine.
By 1876, Otto and Langen succeeded in creating the first internal combustion engine that compressed the fuel mixture prior to combustion for far higher efficiency than any engine created to this time.

Daimler and Maybach left their employ at Otto and Cie and developed the first high-speed Otto engine in 1883. In 1885, they produced the first automobile to be equipped with an Otto engine. The [[Daimler Reitwagen|Daimler ''Reitwagen'']] used a hot-tube ignition system and the fuel known as Ligroin to become the world's first vehicle  powered by an internal combustion engine. It used a four-stroke engine based on Otto's design. The following year, [[Karl Benz]] produced a four-stroke engined automobile that is regarded as the first car.<ref>Ralph Stein (1967). The Automobile Book. Paul Hamlyn Ltd</ref>

In 1884, Otto's company, then known as Gasmotorenfabrik Deutz (GFD), developed electric ignition and the carburetor. In 1890, Daimler and Maybach formed a company known as [[Daimler-Motoren-Gesellschaft|Daimler Motoren Gesellschaft]]. Today, that company is [[Daimler-Benz]].

=== Atkinson cycle ===
[[Image:Prius2004.JPG|thumb|230px|This 2004 [[Toyota Prius]] hybrid has an Atkinson-cycle engine as the petrol-electric hybrid engine]]
[[Image:T cycle AtkinsonMiller.png|thumb|170px|The Atkinson Gas Cycle]]
{{main|Atkinson cycle}}

The Atkinson-cycle engine is a type of single stroke internal combustion engine invented by [[James Atkinson (inventor)|James Atkinson]] in 1882. The Atkinson cycle is designed to provide efficiency at the expense of [[power density]], and is used in some modern hybrid electric applications.

The original Atkinson-cycle piston engine allowed the intake, compression, power, and exhaust strokes of the four-stroke cycle to occur in a single turn of the crankshaft and was designed to avoid infringing certain patents covering Otto-cycle engines.<ref name=pat367496>{{cite patent|country=US|number=367496|inventor=J. Atkinson|title=Gas Engine|gdate=1887-08-02}}</ref>

Due to the unique [[crankshaft]] design of the Atkinson, its expansion ratio can differ from its compression ratio and, with a power stroke longer than its compression stroke, the engine can achieve greater [[thermal efficiency]] than a traditional piston engine. While Atkinson's original design is no more than a historical curiosity, many modern engines use unconventional valve timing to produce the effect of a shorter compression stroke/longer power stroke, thus realizing the [[Fuel economy in automobiles|fuel economy]] improvements the Atkinson 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>

===Diesel cycle===
{{Main|Diesel cycle}}
[[File:1 Audi R15.jpg|thumb|right|Audi Diesel R15 at Le Mans]]

The [[diesel engine]] is a technical refinement of the 1876 Otto-cycle engine. Where Otto had realized in 1861 that the efficiency of the engine could be increased by first compressing the fuel mixture prior to its ignition, [[Rudolf Diesel]] wanted to develop a more efficient type of engine that could run on much heavier fuel. The [[Etienne Lenoir|Lenoir]], Otto Atmospheric, and Otto Compression engines (both 1861 and 1876) were designed to run on [[Coal gas|Illuminating Gas (coal gas)]]. With the same motivation as Otto, Diesel wanted to create an engine that would give small industrial companies their own power source to enable them to compete against larger companies, and like Otto, to get away from the requirement to be tied to a municipal fuel supply.{{citation needed|date=June 2023}} Like Otto, it took more than a decade to produce the high-compression engine that could self-ignite fuel sprayed into the cylinder. Diesel used an air spray combined with fuel in his first engine.

During initial development, one of the engines burst, nearly killing Diesel. He persisted, and finally created a successful engine in 1893. The high-compression engine, which ignites its fuel by the heat of compression, is now called the diesel engine, whether a four-stroke or two-stroke design.

The four-stroke diesel engine has been used in the majority of heavy-duty applications for many decades. It uses a heavy fuel containing more energy and requiring less refinement to produce. The most efficient Otto-cycle engines run near 30% thermal efficiency.{{clarify|reason=Did some text about diesel thermal efficiency fall off?|date=October 2021}}