Flat-12
Encyclopedia
A flat-12 is an internal combustion engine
in a flat
configuration, having 12 cylinder
s.
The flat-12 is wider (but significantly lower in height) than a V12
. Despite the advantage of having a lower center of gravity
than a V12, that advantage can be somewhat offset by the need for a higher mounting height in the engine bay to provide clearance for the exhaust system (six runners on either side). Whereas a V12 can be used in front-engined or mid-engined applications, a flat-12 is used exclusively in mid-engined sports cars. In addition, because it has no advantage in terms of vibrations compared to the more commonly used V-12, the design is rarely used on production cars.
Flat-12 engines are generally not true horizontally opposed engines (boxer
), but rather 180° V
-engines. A true boxer has one crank pin per piston, while in the 180° V-engine, two opposing pistons share the same crank pin.
The flat design was used in Formula One
and Endurance racing. However, when wing-cars
requiring air-flow venturis came along in the late 1970s, the wide, flat layout obstructed the airflow and became obsolete.
In 1964-65, at the end of the 1.5 litre F1 era, Ferrari
introduced a flat-12 on the Ferrari 1512 F1, but a more classical V12 was chosen for the new 3 litre F1.
The Porsche 917
endurance racing car (introduced in 1969, for the Sport category) was powered by an air-cooled flat-12. This engine 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 3 litre water-cooled form for their prototypes and Formula One cars.
The Ferrari flat-12 design was successful and influential especially on Italian manufacturers, including Alfa Romeo
, who were also successful in endurance racing with a flat-12. The Tecno
Formula One flat-12 was a failure, however.
A 4.4-5.0 L 180° flat-12 was later introduced by Ferrari
in some of their production models, including the Berlinetta Boxer
and Testarossa
.
Motori Moderni
designed a 3.5 litre flat-12 engine for Subaru
, 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.
In the early 1990s, Mercedes-Benz
built their 3.5 litre M-291 flat-12 engine for endurance racing. This engine employed a clever cylinder-head design in which the exhaust ports are located where the intake ports would normally be (on top of the engine, pointing upwards). The intake ports are then re-located between the intake and exhaust camshafts, just above the spark-plugs, pointing at an outward angle from the vertical. By locating the entire exhaust system on top, rather than underneath the engine, a much lower mounting height was achieved for this engine in the engine-bay of their racing car, the C-291
(and later C-292
). Unfortunately, the engine suffered from oil scavenging problems early on in its development, and although the problem was eventually solved, changes in the rules by FIA
and ACO
effectively doomed the future prospects of what could otherwise have been a competitive engine.
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 aircooled two-cylinder) in the EBR
armored car
.
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
in a flat
Flat engine
A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...
configuration, having 12 cylinder
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
s.
The flat-12 is wider (but significantly lower in height) than a V12
V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....
. Despite the advantage of having a lower center of gravity
Center of gravity
In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions. In a uniform gravitational field, the center of mass serves as the center of gravity...
than a V12, that advantage can be somewhat offset by the need for a higher mounting height in the engine bay to provide clearance for the exhaust system (six runners on either side). Whereas a V12 can be used in front-engined or mid-engined applications, a flat-12 is used exclusively in mid-engined sports cars. In addition, because it has no advantage in terms of vibrations compared to the more commonly used V-12, the design is rarely used on production cars.
Flat-12 engines are generally not true horizontally opposed engines (boxer
Flat engine
A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...
), but rather 180° V
V engine
A V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft...
-engines. A true boxer has one crank pin per piston, while in the 180° V-engine, two opposing pistons share the same crank pin.
The flat design was used in Formula One
Formula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...
and Endurance racing. However, when wing-cars
Ground effect in cars
Ground effect is term applied to a series of aerodynamic effects used in car design, which has been exploited to create downforce, particularly in racing cars. This has been the successor to the earlier dominant aerodynamic theory of streamlining...
requiring air-flow venturis came along in the late 1970s, the wide, flat layout obstructed the airflow and became obsolete.
In 1964-65, at the end of the 1.5 litre F1 era, Ferrari
Ferrari
Ferrari S.p.A. is an Italian sports car manufacturer based in Maranello, Italy. Founded by Enzo Ferrari in 1929, as Scuderia Ferrari, the company sponsored drivers and manufactured race cars before moving into production of street-legal vehicles as Ferrari S.p.A. in 1947...
introduced a flat-12 on the Ferrari 1512 F1, but a more classical V12 was chosen for the new 3 litre F1.
The Porsche 917
Porsche 917
The Porsche 917 is a racecar that gave Porsche its first overall wins at the 24 Hours of Le Mans in 1970 and 1971. Powered by the Type 912 flat-12 engine of 4.5, 4.9, or 5 litres, the 917/30 variant was capable of a 0- time of 2.3 seconds, 0– in 5.3 seconds, and a top speed of over .There are 6...
endurance racing car (introduced in 1969, for the Sport category) was powered by an air-cooled flat-12. This engine was an evolution of the Porsche flat-8
Flat-8
A flat-8 or horizontally opposed-8 is an internal combustion engine in flat configuration, having 8 cylinders.The most famous engine of this type is the Porsche air-cooled flat-8 engine introduced in a 1.5 L version for Formula One that grew up to a 3 L version used in the Porsche 908.Another...
boxer engine and used identical cylinders to those found on the 908
Porsche 908
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 under Ferdinand Piech....
, but differed in that it used a V12 type crankshaft.
The domination of the Porsche 917 over the V12
V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....
-powered Ferrari 512
Ferrari 512
Ferrari 512 S was the designation of 25 five litre sports cars built until January 1970, 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...
probably influenced Ferrari, because they returned to the flat-12 in 3 litre water-cooled form for their prototypes and Formula One cars.
The Ferrari flat-12 design was successful and influential especially on Italian manufacturers, including Alfa Romeo
Alfa Romeo
Alfa Romeo Automobiles S.p.A. is an Italian manufacturer of cars. Founded as A.L.F.A. on June 24, 1910, in Milan, the company has been involved in car racing since 1911, and has a reputation for building expensive sports cars...
, who were also successful in endurance racing with a flat-12. The Tecno
Tecno
Although Tecno is primarily remembered as an Italian kart and racing car constructor they started out as a conventional engineering business manufacturing hydraulic pumps...
Formula One flat-12 was a failure, however.
A 4.4-5.0 L 180° flat-12 was later introduced by Ferrari
Ferrari
Ferrari S.p.A. is an Italian sports car manufacturer based in Maranello, Italy. Founded by Enzo Ferrari in 1929, as Scuderia Ferrari, the company sponsored drivers and manufactured race cars before moving into production of street-legal vehicles as Ferrari S.p.A. in 1947...
in some of their production models, including the Berlinetta Boxer
Ferrari Berlinetta Boxer
A Ferrari Berlinetta Boxer is one of a series of cars produced by Ferrari in Italy between 1973 and 1984. They used a mid-mounted flat-12 engine, replacing the FR layout Daytona, and were succeeded in the Ferrari stable by the Testarossa. It was designed by Leonardo Fioravanti.Production of the...
and Testarossa
Ferrari Testarossa
The Ferrari Testarossa is a 12-cylinder mid-engine sports car manufactured by Ferrari, which went into production in 1984 as the successor to the Ferrari Berlinetta Boxer...
.
Motori Moderni
Motori Moderni
Motori Moderni was a Formula One engine manufacturer from 1985 through 1987. It was established by the experienced Italian engine designer Carlo Chiti....
designed a 3.5 litre flat-12 engine for Subaru
Subaru
; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...
, which would be used in the 1990 Coloni
Enzo Coloni Racing Car Systems
Enzo Coloni Racing Car Systems, commonly referred to simply as Coloni, is an Italian motor racing team and former Formula One racing car constructor. While it has been successful in Formula Three and Formula 3000, the team was one of the least successful in Formula One history...
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
Jiotto Caspita
The Jiotto Caspita is a prototype midship sports car designed and manufactured by Dome for a company named Jiotto in 1988. The car was billed as the F1 on the Road...
supercar
Supercar
Supercar is a term used most often to describe an expensive high end car. It has been defined specifically as "a very expensive, fast or powerful car"...
. This only appeared in a single prototype and was not put into production.
In the early 1990s, Mercedes-Benz
Mercedes-Benz
Mercedes-Benz is a German manufacturer of automobiles, buses, coaches, and trucks. Mercedes-Benz is a division of its parent company, Daimler AG...
built their 3.5 litre M-291 flat-12 engine for endurance racing. This engine employed a clever cylinder-head design in which the exhaust ports are located where the intake ports would normally be (on top of the engine, pointing upwards). The intake ports are then re-located between the intake and exhaust camshafts, just above the spark-plugs, pointing at an outward angle from the vertical. By locating the entire exhaust system on top, rather than underneath the engine, a much lower mounting height was achieved for this engine in the engine-bay of their racing car, the C-291
Mercedes-Benz C291
The Mercedes-Benz C291 was a Sports-prototype racing car introduced for the 1991 World Sportscar Championship season.-Introduction:The 1991 season marked the introduction of the FIA’s new, and controversial, 3.5 litre formula which replaced the highly successful Group C category that had been used...
(and later C-292
Mercedes-Benz C292
The Mercedes-Benz C292 was a stillborn Group C prototype race car intended for the 1992 World Sportscar Championship season as an evolution of the Mercedes-Benz C291, but never raced due to Mercedes-Benz withdrawing from sportscar racing after a dismal 1991 season.Built by Sauber for Mercedes-Benz,...
). Unfortunately, the engine suffered from oil scavenging problems early on in its development, and although the problem was eventually solved, changes in the rules by FIA
Fédération Internationale de l'Automobile
The Fédération Internationale de l'Automobile is a non-profit association established as the Association Internationale des Automobile Clubs Reconnus on 20 June 1904 to represent the interests of motoring organisations and motor car users...
and ACO
Automobile Club de l'Ouest
The Automobile Club de l'Ouest , sometimes abbreviated to ACO, is the largest automotive group in France. It was founded in 1906 by car building and racing enthusiasts, and is most famous for being the organising entity behind the annual Le Mans 24 Hours race...
effectively doomed the future prospects of what could otherwise have been a competitive engine.
Henry Meadows
Henry Meadows
Henry Meadows of Wolverhampton, England were major suppliers of engines and transmissions, to the smaller companies in the British motor industry...
built a flat-12 petrol engine in World War II for the British Covenanter tank
Covenanter tank
The Tank, Cruiser, Mk V, Covenanter was a British Cruiser tank of the Second World War. It was named for the Covenanters, a Scottish religious faction in the British Isles at the time of the Wars of the Three Kingdoms...
. In 1954, Panhard
Panhard
Panhard is currently a French manufacturer of light tactical and military vehicles. Its current incarnation was formed by the acquisition of Panhard by Auverland in 2005. Panhard had been under Citroën ownership, then PSA , for 40 years...
fitted a flat-12 (based on its earlier aircooled two-cylinder) in the EBR
Panhard EBR
The Panhard EBR is a light armoured car designed by Panhard for the French Army and later used across the globe, notably by the French Army during the Algerian War and the Portuguese Army during the Portuguese Colonial War in Angola, Mozambique and Guinea-Bissau.The EBR is an 8x8 wheeled...
armored car
Armored car (valuables)
A common meaning of armored car is as an armored van or truck, used in transporting valuables, such as large quantities of money . The armored car is a multifunctional vehicle designed to protect and ensure the well being of the transported individuals and/or contents...
.