Editing Petrol engine (section)

==Design==

=== Thermodynamic cycle ===
[[File:4StrokeEngine Ortho 3D Small.gif|thumb|right|upright=0.8|Animation of an Otto cycle engine]]

Most petrol engines use either the four-stroke [[Otto cycle]] or the [[two-stroke engine|two-stroke cycle]].<ref>{{cite web |title=What is Otto Cycle - Complete Explaintion on P-v & T-s Diagram |url=https://www.theengineerspost.com/otto-cycle/ |website=The Engineers Post |access-date=14 August 2022 |language=en-us |date=10 September 2019}}</ref><ref>{{cite web |title=What is Two Stroke Engine?- Types, And Working |url=https://www.engineeringchoice.com/what-is-two-stroke-engine/ |website=Engineering Choice |access-date=14 August 2022 |language=en-us |date=12 November 2020}}</ref><ref>{{cite web |title=Two Stroke Engine - Internal Combustion Engines (IC) - Automobile Magazine |url=https://www.motortrend.com/news/two-stroke-engines-expected-revival/ |website=MotorTrend |access-date=14 August 2022 |language=en |date=16 December 2009}}</ref> Petrol engines have also been produced using the [[Miller cycle]] and [[Atkinson cycle]].<ref>{{cite web |title=How does a Miller-cycle engine work? |url=https://auto.howstuffworks.com/question132.htm |website=HowStuffWorks |access-date=14 August 2022 |language=en-us |date=1 April 2000}}</ref><ref>{{cite web |title=Mazda 2.3L Miller-cycle DOHC V-6 |url=https://www.wardsauto.com/news-analysis/mazda-23l-miller-cycle-dohc-v-6 |website=WardsAuto |access-date=14 August 2022 |language=en |date=1 January 1998}}</ref><ref>{{cite web |title=Why does Toyota use Atkinson cycle engines? |url=https://mag.toyota.co.uk/toyota-use-atkinson-cycle-engines/ |website=Toyota UK Magazine |access-date=14 August 2022 |date=14 January 2015}}</ref><ref>{{cite web |date=4 April 2016 |title=Engine Types: Atkinson Cycle vs Otto vs Miller |url=https://enginehoist.net/engine-types-atkinson-cycle-vs-otto-vs-miller/ |access-date=9 June 2023 |website=EngineHoist}}</ref>

=== Layout ===
Most petrol-powered piston engines are [[straight engine]]s or [[V engine]]s. However, [[flat engine]]s, [[W engine]]s and [[Engine_configuration#Other_layouts|other layouts]] are sometimes used. 

[[Engine_configuration#Wankel_(rotary)_engines|Wankel engines]] are classified by the number of rotors used.

=== Compression ratio ===
{{main|Compression ratio#Petrol engines}}

===Cooling===
{{main|Internal combustion engine cooling}}

Petrol engines are either [[Air-cooled engine|air-cooled]] or [[Water_cooling#Internal_combustion_engines|water-cooled]].

===Ignition===
{{main|Ignition system}}
Petrol engines use [[spark ignition]]. [[High voltage]] for the spark this may be provided by a [[ignition magneto|magneto]] or an [[ignition coil]].  In modern car engines, the [[ignition timing]] is managed by an electronic [[Engine Control Unit]]. Ignition modules can also function as a rev limiter in some cases to prevent overrevving and the consequences of it, such as valve float and connecting rod failure.

=== Primer ===

Primers may be used to help start the engine. They can draw fuel from fuel tanks and vaporize fuel directly into piston cylinders. Engines are difficult to start during cold weather, and the fuel primer helps because otherwise there will not be enough heat available to vaporize the fuel in the [[carburetor]].<ref>{{Cite PHAK|year=2023|chapter=7|page=25}}</ref>