Editing Flat-four engine (section)

=== 1936–1999 ===
{{More citations needed section|date=December 2023}}
{{multiple image
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| image1            = Flat Four Jowett Engine from a Jowett Jupiter.jpg
| caption1          = 1952 [[Jowett Jupiter]] water-cooled engine
| image2            = 1955 Porsche 550 Spyder engine.jpg
| caption2          = 1955 [[Porsche 550 Spyder]] air-cooled engine
}}

The 1936 [[Tatra T97]] pioneered the rear-engined, air-cooled flat-four, backbone chassis layout (later used by the [[Volkswagen Beetle]]), and at the same time, though unrelated, came the [[Steyr 50]] from Austria, sporting a front boxer 4 engine with rear wheel drive. Also in 1936, English company [[Jowett Cars|Jowett]] expanded its model range from flat-twin engines to also include flat-four engines. Production of Jowett flat-four engines continued until 1954, when the [[Jowett Javelin]] saloon and [[Jowett Jupiter]] sports models ended production.

The longest production flat-four engine is the [[Volkswagen air-cooled engine]], which was produced from 1938 until 2006 and was most famously used in the rear-engined 1938–2003 [[Volkswagen Beetle]] and 1950–1983 [[Volkswagen Transporter]].<ref>{{cite news |title=The engine that Benz built still survives |url=https://www.theglobeandmail.com/globe-drive/reviews/classics/the-engine-that-benz-built-still-survives/article4317376/ |newspaper=The Globe and Mail |date=29 April 2010 |access-date=1 September 2019}}</ref> This air-cooled engine was designed by Porsche and was also used in the 1948–1965 [[Porsche 356]], 1953–1956 [[Porsche 550]], 1965–1969 [[Porsche 912]] and 1969–1976 [[Porsche 914]]. In 1984, to comply with exhaust emissions regulations a water-cooled version called the [[Volkswagen Wasserboxer engine]] was introduced in the [[Volkswagen Type 2 (T3)|Volkswagen Transporter (T3)]]

During the 1960s and 1970s, several manufacturers produced flat-four engines including the air-cooled [[Citroën GS#Mechanics|Citroën flat-four engine]], the water-cooled [[Alfa Romeo Flat-4 engine|Alfa Romeo flat-four engine]], the water-cooled [[Lancia Flat-4 engine|Lancia flat-four engine]] and the water-cooled [[Subaru EA engine]].

Two important engines designed during this period, but never saw the light of day in series production, were the Morris 800cc side valve engine by Alec Issigonis in 1947 originally destined for the Morris Minor, and the Ferguson 2.2 litre SOHC engine by Claude Hill in 1966 as part of the R5 vehicle research project.