Flat-12 engine

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Ferrari Testarossa flat-twelve engine, mid-mounted

A flat-12 is a 12-cylinder internal combustion engine in a flat configuration. Rarer, wider, and less tall than a V12, the flat-12 design was used in Formula One and endurance racing and some exotic sports cars.

Flat-12 engines are generally not horizontally opposed engines (boxers), but rather 180° V-engines. A true boxer has one crankpin journal per piston, while in the 180° V-engine, two opposing pistons share the same crankpin journal; the engine also has a naturally lower center of gravity than a V12, but, with the exception of the Mercedes-Benz C291, is mounted somewhat higher in the engine bay to provide clearance for the exhaust system.

Racing cars[edit]

Porsche 360 / Cisitalia Grand Prix[edit]

Ferdinand Porsche can be credited for creating the first flat-12 engined car, the supercharged Porsche 360 / Cisitalia Grand Prix, near Gmünd in 1947 but the car never raced.[1]


In 1964-65, Ferrari introduced a flat-12 in the Ferrari 1512 F1 car [2] and won the F1 world championship with a flat-12 layout in the mid- and late 1970s with the Ferrari 312T.[3][4] However, when wing-cars requiring air-flow venturis came along in the late 1970s, the wide flat shape obstructed the airflow and was considered obsolete. A 4.4-5.0 L 180° flat-12 was also introduced by Ferrari in some of their production models, including the Berlinetta Boxer and Testarossa.

Alfa Romeo[edit]

The success of the flat-12 design had an influence on Italian manufacturers, including Alfa Romeo, they were unsuccessful with their return to Formula 1 with the flat-12 powered 177, but succeeded in endurance racing with the 33TT12 and 33SC12.

Porsche 917[edit]

The Porsche 917 endurance racing car (introduced in 1969, for the sport category) was powered by an air-cooled flat-12; this was an evolution of the Porsche flat-8 boxer engine and used identical cylinders to those found on the 908, but differed in that it used a V12 type crankshaft. The domination of the Porsche 917 over the V12-powered Ferrari 512 probably influenced Ferrari, because they returned to the flat-12 in three-litre water-cooled form for their prototypes and Formula One cars.

Motori Moderni[edit]

Motori Moderni designed a 3.5-litre flat-12 engine for Subaru, the 1235, which would be used in the 1990 Coloni Formula One car. The Coloni−Subaru was not competitive and did not start a Grand Prix; the Motori Moderni flat-12 engine also appeared in detuned form in the Jiotto Caspita supercar. This only appeared in a single prototype and was not put into production.

Tecno F1[edit]

The Tecno Formula One flat-12 was a failure.


In the early 1990s, Mercedes-Benz built a 3.5-litre M-291 flat-12 engine for endurance racing. 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. Putting the exhaust system on top, rather than underneath, allowed the engine to ride much lower in the engine-bay of the C-291 (and later C-292).

The engine suffered from oil scavenging problems early in development, and although the problem was eventually solved, changes in the rules by the FIA and ACO doomed its prospects.

Military vehicles[edit]

Henry Meadows built a flat-12 petrol engine in World War II for the British Covenanter tank.

In 1954, Panhard fitted a flat-12 (based on its earlier air-cooled two-cylinder) in the EBR armored car.[5]


Franklin 12 was a series of air-cooled flat-12 aircraft engines produced by Franklin Engine Company in the 1940s and 1950s.

See also[edit]

Ferrari flat-12 engine


  1. ^ https://www.stuttcars.com/about-porsche/museum-gmund/ Retrieved 6 April 2017.
  2. ^ http://www.ultimatecarpage.com/car/139/Ferrari-1512-F1.html Retrieved 6 April 2017.
  3. ^ https://www.formula1.com/en/championship/drivers/hall-of-fame/Niki_Lauda.html Retrieved 6 April 2017.
  4. ^ https://www.formula1.com/en/championship/drivers/hall-of-fame/Jody_Scheckter.html Retrieved 6 April 2017.
  5. ^ Ogorkiewicz, R. M. AFV Weapons Profile 039 Panhard Armoured Cars (Windsor, Berks: Profile Publications).