A flat-twelve engine, also known as a horizontally opposed-twelve, is a twelve-cylinder piston engine with six cylinders on each side of a central crankshaft.
Flat-twelve engines are less common than V12 engines, but they have been used in various racing cars during the 1960s and 1970s, and in mid-engined Ferrari road cars from 1973 to 1996.
Unlike most flat-twin, flat-four, and flat-six engines, flat-twelve engines typically use the crankshaft configuration of a 180° V engine. Instead of the boxer engine design of each piston having its own crankpin, flat-twelve engines have each pair of pistons sharing a crankpin, and thus are flat, but not true boxers.
Compared with a V12 engine, a flat-twelve has a lower center of gravity, but because a flat-twelve is wider they are rarely used in front-engined cars.
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 1.5 L (92 cu in). [1] One engine was built and the car conducted top speed testing, but it never competed in any races. [2]
In 1964–65, the Ferrari 512 F1 competed in several Formula One races. [3] The 512 F1 was powered by a 1.5 L (92 cu in) 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. [4] [5] 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.
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 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 33TT12 and 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.
From 1973 to 1996, Ferrari used flat-twelve engines in various production models: the 1973-1976 Ferrari 365 GT/4 BB, the 1976-1981 Ferrari 512 BB, the 1981-1984 Ferrari 512 BBi, the 1984-1991 Ferrari Testarossa, the 1991-1994 Ferrari 512 TR and the 1994-1996 Ferrrari F512 M.
During World War II, the British Covenanter tank was powered by a Meadows D.A.V flat-12, 340 hp (250 kW) and the Churchill by a 350 hp (261 kW) Bedford engine flat 12. [6] Another military vehicle usage was the Panhard EBR armored cars during the 1950s. [7]
During the 1940s, the Franklin Engine Company in the United States produced a flat-twelve aircraft engine called the O-805-2. [8]
A V12 engine is a twelve-cylinder piston engine where two banks of six cylinders are arranged in a V configuration around a common crankshaft. V12 engines are more common than V10 engines. However, they are less common than V8 engines.
A V6 engine is a six-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.
A V10 engine is a ten-cylinder piston engine where two banks of five cylinders are arranged in a V configuration around a common crankshaft. V10 engines are much less common than V8 and V12 engines. Several V10 diesel engines have been produced since 1965, and V10 petrol engines for road cars were first produced in 1991 with the release of the Dodge Viper.
A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, whereby each cylinder has two pistons sharing a central combustion chamber.
A straight-four engine is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.
The Ferrari Berlinetta Boxer (BB) is series of sports cars produced by Ferrari in Italy between 1973 and 1984. The BB was designed by Leonardo Fioravanti at Pininfarina. The first BB model, the 365 GT4 BB, replaced the front engined Daytona and was the first in a series of road-going Ferraris equipped with a mid-mounted flat-twelve engine. It was also the first mid-engined road-car to bear the Ferrari name and the Cavallino Rampante logo. The 365 GT4 BB was succeeded in 1976 by the BB 512, equipped with a larger displacement engine, then by the fuel-injected BB 512i in 1981. The series was discontinued in 1984 when the BB 512i was replaced by the Testarossa, which used a revised version of the flat-twelve engine.
The Porsche 917 is a sports prototype race car developed by German manufacturer Porsche to exploit the regulations regarding the construction of 5-litre sports cars. Powered by a Type 912 flat-12 engine which was progressively enlarged from 4.5 to 5.0 litres, the 917 was introduced in 1969 and initially proved unwieldy on the race track but continuous development improved the handling and it went on to dominate sports-car racing in 1970 and 1971. In 1970 it gave Porsche its first overall win at the 24 Hours of Le Mans, a feat it would repeat in 1971. It would be chiefly responsible for Porsche winning the International Championship for Makes in 1970 and 1971. Porsche went on to develop the 917 for Can-Am racing, culminating in the twin-turbocharged 917/30 which was even more dominant in the role. Porsche drivers would win the Can-Am championship in 1972 and 1973. 917 drivers also won the Interserie championship every year from 1969 to 1975.
Ferrari 512 S is the designation for 25 sports cars built in 1969–70, with five-litre 12-cylinder ("512") engines, related to the Ferrari P sports prototypes. The V12-powered cars were entered in the 1970 International Championship for Makes by the factory Scuderia Ferrari and private teams. Later that year, modified versions resembling their main competitor, the Porsche 917, were called Ferrari 512 M. In the 1971 International Championship for Makes, the factory focused on the new Ferrari 312 PB and abandoned the 512 which was only entered by privateers. From 1972 onwards, the 512 was withdrawn from the world championship following a change in the regulations, and some 512s in private hands were entered in CanAm and Interserie races.
A flat-eight engine, also called a horizontally-opposed eight, is an eight-cylinder piston engine with two banks of four inline cylinders, one on each side of a central crankshaft, 180° apart.
A flat-sixteen engine, also known as a horizontally opposed-sixteen, is a sixteen-cylinder piston engine with eight cylinders on each side of a central crankshaft.
The Porsche 908 was a racing car from Porsche, introduced in 1968 to continue the Porsche 906-Porsche 910-Porsche 907 series of models designed by Helmuth Bott (chassis) and Hans Mezger (engine) under the leadership of racing chief Ferdinand Piëch.
The Alfa Romeo Tipo 33 was a sports racing prototype raced by the Alfa Romeo factory-backed team between 1967 and 1977. These cars took part for Sport Cars World Championship, Nordic Challenge Cup, Interserie and CanAm series. A small number of road going cars were derived from it in 1967, called Alfa Romeo 33 Stradale.
The 1970 24 Hours of Le Mans was the 38th Grand Prix of Endurance and took place on 13 and 14 June 1970. It was the 8th stage of the 1970 World Sportscar Championship season.
Group 5 was an FIA motor racing classification which was applied to four distinct categories during the years 1966 to 1982. Initially Group 5 regulations defined a Special Touring Car category and from 1970 to 1971 the classification was applied to limited production Sports Cars restricted to 5 litre engine capacity. The Group 5 Sports Car category was redefined in 1972 to exclude the minimum production requirement and limit engine capacity to 3 litres. From 1976 to 1982 Group 5 was for Special Production Cars, a liberal silhouette formula based on homologated production vehicles.
The Ferrari 312 PB was a Group 6 Prototype-Sports Car introduced in 1971 by Italian carmaker Ferrari. It was officially designated the 312 P, but often known as the 312 PB to avoid confusion with a previous car of the same name. It was part of the Ferrari P series of Prototype-Sports Cars but was redesignated as a Group 5 Sports Car for 1972.
This article gives an outline of Formula One engines, also called Formula One power units since the hybrid era starting in 2014. Since its inception in 1947, Formula One has used a variety of engine regulations. Formulae limiting engine capacity had been used in Grand Prix racing on a regular basis since after World War I. The engine formulae are divided according to era.
A V8 engine is an eight-cylinder piston engine in which two banks of four cylinders share a common crankshaft and are arranged in a V configuration.
The Ferrari flat-12 engine family is a series of flat-12 DOHC petrol engines produced by Ferrari from 1964 to 1996. The first racing Ferrari flat-12, the Mauro Forghieri-designed Tipo 207, was introduced in the Ferrari 1512 F1 car in 1964. Later flat-12 racing engines were used in Ferrari Formula One and sports racing cars from 1968 until 1980, including the 212 E Montagna, 312 B series, 312 PB and 312 T series. The roadgoing flat-12 engines were introduced with the 365 GT4 BB and were produced in various versions until the end of F512M production in 1996.
Ferrari has made a number of V12 racing engines designed for Formula One; made between 1950 and 1995. Some derived engines were also used in various Ferrari sports prototype race cars and production road cars.
The Porsche Type 573 engine is a naturally-aspirated, flat-eight racing engine, designed by Porsche for Formula One racing; and used for a single season in 1962 in the 1½ litre formula.
