Editing Wankel engine (section)

==Advantages==
Prime advantages of the Wankel engine are:<ref name="PS-April-1966">{{cite magazine |url= https://books.google.com/books?id=nSkDAAAAMBAJ&q=Curtis-Wright+RC2-60&pg=PA102 |title=Test Drive of a US car with a rotating combustion engine |first1=Jan P. |last1=Norbye |pages=102–107 |magazine=Popular Science |date=April 1966 |volume=188 |issue=4 |access-date=2018-05-05}}</ref>
* A far higher [[power-to-weight ratio]] than a piston engine<ref name="Ansdale Keller 1971 p. 205">{{cite book |last1=Ansdale |first1=R.F. |last2=Keller |first2=H. |title=Der Wankelmotor: Konstruktion und Wirkungsweise |place=Stuttgart| publisher=Motorbuch-Verlag |year=1971 |language=de |page=205}}</ref>
* Easier to package in small engine spaces than an equivalent piston engine<ref name="Ansdale Keller 1971 p. 205"/>
* Able to reach higher engine speeds than a comparable piston engine
* Operating with almost no vibration<ref name="Ansdale Keller 1971 p. 203"/>
* Not prone to [[Engine knocking|engine-knock]]<ref name="Bensinger 1973 p. 86"/><ref name="Yamamoto_1971_104"/><ref name="K. Yamamoto, T. Muroki 1972"/>
* Cheaper to mass-produce, because the engine contains fewer parts<ref name="Ansdale Keller 1971 p. 205"/>
* Supplying torque for about two-thirds of the combustion cycle rather than one-quarter for a piston engine<ref name="Ansdale Keller 1971 p. 203">{{cite book |last1=Ansdale |first1=R.F. |last2=Keller |first2=H. |title=Der Wankelmotor: Konstruktion und Wirkungsweise |place=Stuttgart| publisher=Motorbuch-Verlag |year=1971 |language=de |page=203}}</ref>
* Easily adapted and highly suitable to use hydrogen fuel.

Wankel engines are considerably lighter and simpler, containing far fewer moving parts than piston engines of equivalent power output. [[poppet valve|Valves or complex valve trains]] are eliminated by using simple ports cut into the walls of the rotor housing. Since the rotor rides directly on a large bearing on the output shaft, there are no [[connecting rod]]s and no [[crankshaft]]. The elimination of reciprocating mass gives Wankel engines a low non-uniformity coefficient, meaning that they operate much smoother than comparable reciprocating piston engines. For example, a two-rotor Wankel engine is more than twice as smooth in its operation as a four-cylinder reciprocating piston engine.<ref name="Bensinger 1973 p. 72"/>

A four-stroke cylinder produces a power stroke only every other rotation of the crankshaft, with three strokes being pumping losses. The Wankel engine also has higher volumetric efficiency than a reciprocating piston engine.<ref name="s4PSp">{{cite book|last1=Ansdale |first1=Richard F. |year=1995 |title=Der Wankelmotor. Konstruktion und Wirkungsweise |publisher=Motorbuch-Verlag |pages=73, 91–92, 200 |isbn=978-3-87943-214-1 |language=de}}</ref> Because of the quasi-overlap of the power strokes, the Wankel engine is very quick to react to power increases, delivering power quickly when demanded, especially at higher engine speeds. This difference is more pronounced relative to four-cylinder reciprocating engines and less pronounced relative to higher cylinder counts.

Due to the absence of hot exhaust valves, the fuel [[octane rating|octane]] requirements of Wankel engines are lower than in reciprocating piston engines.<ref name="Bensinger 1973 p. 85"/> As a rule of thumb, it may be assumed that a Wankel engine with a working chamber volume V<sub>k</sub> of 500&nbsp;cm<sup>3</sup> and a compression of ε=9 runs well on mediocre-quality petrol with an octane rating of just 91&nbsp;RON.<ref name="Bensinger 1973 p. 86"/> If in a reciprocating piston engine, the compression must be reduced by one unit of compression to avoid knock, then, in a comparable Wankel engine, a reduction in compression may not be required.<ref name="Bensinger 1973 p. 88">{{cite book |last1=Bensinger |first1=Wolf-Dieter |title=Rotationskolben-Verbrennungsmotoren |place=Berlin, Heidelberg, New York |date=1973 |isbn=978-3-540-05886-1 |oclc=251737493 |language=de |page=88}}</ref>

Because of the lower injector count, fuel injection systems in Wankel engines are cheaper than in reciprocating piston engines. An injection system that allows [[Stratified charge engine|stratified charge]] operation may help reduce rich mixture areas in undesirable parts of the engine, which improves fuel efficiency.<ref name="Bensinger 1973 p. 82–83">{{cite book |last1=Bensinger |first1=Wolf-Dieter |title=Rotationskolben-Verbrennungsmotoren |place=Berlin, Heidelberg, New York |date=1973 |isbn=978-3-540-05886-1 |oclc=251737493 |language=de |pages=82–83}}</ref>