Editing Flat-twelve engine (section)

==Racing cars==
=== Formula One ===
The first known flat-twelve engine was built by Porsche in 1947 for the abandoned [[Cisitalia Grand Prix]] racing car. The engine, known as the Porsche Typ 360, was supercharged and had a displacement of {{convert|1.5|L|cuin|0|abbr=on}}.<ref>{{cite web |title=Cisitalia Grand Prix (Porsche type 360) |url=https://www.stuttcars.com/porsche-models/360/ |website=www.stuttcars.com |access-date=6 October 2019 |language=en}}</ref> One engine was built and the car conducted top speed testing, but it never competed in any races.<ref name="stevemckelvie">{{cite web |url=https://stevemckelvie.files.wordpress.com/2013/01/cisitalia-build-story-by-martin-schroeder.pdf |title=Cisitalia 360 Grand Prix Car |website=stevemckelvie.files.wordpress.com |url-status=dead |archive-url=https://web.archive.org/web/20150227010337/https://stevemckelvie.files.wordpress.com/2013/01/cisitalia-build-story-by-martin-schroeder.pdf |archive-date= 27 February 2015}}</ref>

In 1964–65, the [[Ferrari 158#Ferrari 1512|Ferrari 512 F1]] competed in several Formula One races.<ref>{{cite web |title=1964 - 1965 Ferrari 1512 F1 - Images, Specifications and Information |url=http://www.ultimatecarpage.com/car/139/Ferrari-1512-F1.html |website=www.ultimatecarpage.com |access-date=5 October 2019}}</ref> The 512 F1 was powered by a {{convert|1.5|L|cuin|0|abbr=on}} flat-twelve engine and raced alongside the V8-engined Ferrari 158 upon which it was based. Ferrari returned to using flat-twelve engines in 1970, when the [[Ferrari 312B]] switched from the V12 engine used by its predecessor. Its successor, the [[Ferrari 312T]], was introduced in 1975 and won the Formula One constructors championships from 1975 to 1979.<ref>{{cite web |title=Niki Lauda |url=https://www.formula1.com/en/championship/drivers/hall-of-fame/Niki_Lauda.html |website=www.formula1.com |access-date=5 October 2019 |language=en}}</ref><ref>{{cite web |title=Jody Scheckter |url=https://www.formula1.com/en/championship/drivers/hall-of-fame/Jody_Scheckter.html |website=www.formula1.com |access-date=5 October 2019 |language=en}}</ref> The success of the Ferrari 312T led other Formula One teams to build flat-twelve engines, such as the 1979 [[Alfa Romeo 177]].

In 1990, the [[Subaru 1235]] flat-twelve engine was built for Subaru's unsuccessful attempt to compete in Formula One as an engine manufacturer.

=== Sports car racing ===
{{Listen|filename=Porsche 917 40th Anniversary.ogg|title=Porsche 917 flat-12|description=Eleven 917s pull away at Goodwood Festival of Speed 2009}}
In 1969, the [[Porsche 917]] sports prototype racing car introduced an air-cooled flat-twelve engine. This flat-twelve engine was based on the previous flat-eight engine, but it used a V12 crankshaft configuration instead of the [[boxer engine|boxer]] configuration used by the flat-eight. The domination of the Porsche 917 probably influenced Ferrari, because they switched from V12 engines to flat-twelve engines (using a boxer configuration) for the [[Ferrari 312 PB]], which competed from 1971 to 1973. Alfa Romeo also used flat-twelve engines in the 1973-1976 [[Alfa Romeo Tipo 33#Alfa Romeo 33TT12|Alfa Romeo 33TT12]] and [[Alfa Romeo Tipo 33#Alfa Romeo 33SC12|Alfa Romeo 33SC12]] sports prototype racing cars.

For the 1991 sports-prototype racing category, Mercedes-Benz switched from a twin-turbo V8 engine to a naturally-aspirated flat-twelve engine for in the [[Mercedes-Benz C291]] racing car. This engine employed a cylinder-head design with exhaust ports where the intake ports would normally be (on top of the engine, pointing upwards). The intake ports are between the intake and exhaust camshafts, just above the spark-plugs, pointing at an outward angle from the vertical. This was done to allow the engine to be installed lower in the chassis. The C291 was unsuccessful and Mercedes withdrew from sports-prototype racing after the 1991 season.