V12 engine

Each bank of a V12 engine essentially functions as a straight-six engine, which by itself has perfect primary and secondary engine balance. By using the correct V-angle, a V12 engine can therefore have perfect balance. The even firing order for a four-stroke V12 engine has an interval of 60 degrees, therefore a V12 engine can be perfectly balanced if a V-angle of 60 degrees, 120 degrees or 180 degrees is used. Many V12 engines use a V-angle of 60 degrees between the two banks of cylinders.[1] V12 engines with other V-angles have been produced, sometimes using split crankpins to reduce the unbalanced vibrations. The drawback of a V12 engine is the extra cost, complexity and friction losses compared with engines containing fewer cylinders.

At any given time, three of the cylinders in a V12 engine are in their power stroke, which increases the smoothness of the power delivery by eliminating gaps between power pulses.

A V12 engine with a 180 degree V-angle is often called a flat-twelve engine (or a 'boxer twelve'). However, this terminology is incorrect for the majority of 180-degree V12 engines, since they use shared crankpins and are therefore not configured as flat engines.[2]

Theoretically, the rotating parts of a V12 racing engine could be lighter than a crossplane V8 engine of similar displacement, due to the V12 engine not requiring counterweights on the crankshaft or as much inertial mass for the flywheel. In addition, the exhaust system of a V12 engine is much simpler than would be required for a crossplane V8 engine to achieve pulsed exhaust gas tuning. However, use of V12 engines in motor racing is uncommon in the 21st century.

A 60-degree V12 engine is typically narrower than a 90-degree V6 or V8 engine of similar displacement. However, the V12 engine is usually longer than V6 and V8 engines. The added length often makes it difficult to fit a V12 engine into a passenger car, but the length is not typically a problem for trucks engines and stationary engines. Due to its narrower width, the V12 is common in locomotive, armoured tank and marine engines. In these applications, the width of the engine is constrained by tight railway clearances or street widths, while the length of the vehicle is more flexible.

In twin-propeller boats, two V12 engines can be narrow enough to sit side-by-side, while three V12 engines are sometimes used in high-speed three-propeller configurations. Large, fast cruise ships can have six or more V12 engines. In historic piston-engine fighter and bomber aircraft, the long, narrow V12 configuration used in high-performance aircraft made them more streamlined than other engines, particularly the short, wide radial engine.

1917 Liberty L-12 airplane engine

Renault 12Dc airplane engine, circa 1925

Five years after the first V12 engine was introduced, Renault introduced the first V12 engine for aircraft in 1909. This engine had a V-angle of 60 degrees, air cooling and an intake over exhaust (F-head) valve arrangement. It had a displacement of 12.2 L (740 cu in), a weight of 350 kg (772 lb) and produced 103 kW (138 hp) at 1,800 rpm. The propeller was driven from the front end of the camshaft, thus spinning the propellor speed at half the speed of a typical crankshaft driven propellor, in order to improve the propellor efficiency.[4] The Renault engine was closely mimicked by the RAF 4 and its derivatives, which was used by various British military aircraft during World War I. The RAF 4 engine had a displacement of 13.2 L (806 cu in), weighed 289 kg (637 lb) and produced 104 kW (140 hp) at 1,800 rpm.

In March 1914, a prototype version of the Sunbeam Mohawk V12 engine was unveiled in the United Kingdom, based on the 'Toodles V' motor racing engine. The production version was rated at 168 kW (225 hp) at 2,000 rpm, making it the most powerful airplane engine in Great Britain at the outbreak of World War I.[4] During and after World War I, various companies in the United States produced the Liberty L-12 engine. In Austria, the Austro Daimler V12 engines were used by the large flying boats of the Naval Air Force and produced up to 257 kW (345 hp). By the end of World War I, V12s were well established in aviation, powering some of the newest and largest fighter and bomber airplanes.

After World War I, many Zeppelins used V12 engines built by Maybach and Daimler. V12 engines powered the first transatlantic crossings by the Curtiss NC flying boats (using four Liberty L-12 engines), the first non-stop transatlantic crossing in a Vickers Vimy (using two Rolls-Royce Eagle engines) and the first transatlantic crossing by an airship in the R-34 class airship (using five Sunbeam Maori engines).

1946 Rolls-Royce Merlin airplane engine in an Avro York

V12 engines reached their apogee during World War II with engines such as the British Rolls-Royce Merlin and Rolls-Royce Griffon, the Soviet Klimov VK-107 and Mikulin AM-38, the American Allison V-1710, and the German Daimler-Benz DB 600 and Junkers Jumo. These engines generated about 750 kW (1,000 hp) at the beginning of the war and over 1,100 kW (1,500 hp) at their ultimate evolution stage. This rapid increase in power outputs was due to technology such as multi-speed superchargers and high octane fuels, and the V12 layout was commonly adopted due to its low vibrations so that the powerful engines did not tear apart the light airframes of fighters.

The Allied forces used V12 engines with an "upright" design, while many German engines (aside from the BMW VI, which was designed prior to World War II), used an inverted engine design, which had a lower centre of gravity and improved pilot visibility for single-engined designs. The only American-design inverted V12 engine of any type to see even limited service in World War II was the air-cooled Ranger V-770, which was used in aircraft that were only used for training purposes within the United States, such as the Fairchild AT-21 Gunner.

The Rolls-Royce Merlin V12 engine was used in several British aircraft including the Hawker Hurricane and Supermarine Spitfire fighters, and the Avro Lancaster and de Havilland Mosquito bombers. The Hurricane and Spitfire playing a vital role in the Battle of Britain. The long, narrow configuration of the V12 contributed to good aerodynamics, while its smoothness allowed its use with relatively light and fragile airframes.

In the United States, the Rolls-Royce Merlin engine was produced under license by Packard Motor Car Company, which was used in the P-51 Mustang fighter. This engine was also incorporated into some models of the Curtiss P-40, specifically the P-40F and P-40L. Packard Merlins powered Canadian-built Hurricane, Lancaster, and Mosquito aircraft, as well as the UK-built Spitfire Mark XVI, which was otherwise the same as the Mark IX with its British-built Merlin. The Allison V-1710 was the liquid-cooled V12 engine designed in the United States that was used on active service during World War II. It was initially used in the P-38 Lightning, but the turbosupercharger system required bulky ductwork and had poor high-altitude performance. In 1943, a version using a more conventional mechanical supercharger began production.

After World War II, V12 engines became generally obsolete in aircraft due to the introduction of turbojet and turboprop engines that had more power for their weight, and fewer complications.

1916 Packard Twin Six engine

One of the earliest recorded uses of V12 engines in automobiles was in October 1913, when a custom-built racing car competed at the Brooklands circuit in the United Kingdom. The car was entered by Louis Coatalen, who was chief engineer of the Sunbeam Motor Car Company. It was named 'Toodles V' (after Coatalen's pet name for his wife) and achieved several speed records in 1913 and 1914.[4] The V12 engine had a displacement of 9.0 L (549 cu in), an aluminum crankcase, iron cylinders with L-shaped combustion chambers, a cam-in-block valvetrain and a V-angle of 60 degrees. Each bank of the engine consisted of two cylinder blocks with three cylinders each. Valve clearance was set by grinding the relevant parts, the engine lacking any easy means of adjustment. This reflected the intention for the engine to be later used in aircraft, since any adjustment method that could go wrong in flight was to be avoided. As initially built, the V12 was rated at 150 kW (200 bhp) at 2,400 rpm and weighed approximately 340 kg (750 lb).

Amongst the first production cars to use a V12 engine were the 1915 Packard Twin Six,[9][10] the 1915 National V12 engine and the 1917 Weidely Pathfinder;[11] all of which were built in the United States.

1931 Cadillac Series 370A engine

Usage of V12 engines in luxury cars increased from the 1920s,[12] including cars such as the 1921 Fiat 520 'Superfiat', the 1926 Daimler Double-Six 50,[13] the 1931 Hispano-Suiza J12, the 1931 Cadillac 370A V-12, the 1932 Auburn V-12 Speedster,[14] the 1931 Lincoln K series, the 1932 Franklin V-12,[15] the 1936 Rolls-Royce Phantom III and the 1936 Pierce-Arrow Twelve.[16] A key benefit of V12 engines during this period was their smoothness, since vibration isolating engine mounts were rarely used prior to the 1930s.

In the United States, V12 engines began to decline in popularity from the 1930s as improvements in combustion chamber design and piston form enabled lighter V8 engines to become more powerful than the V12 engines. The last American V12 engine of the era, the H-Series Lincoln V12 engine, was replaced by a V8 engine in 1949.

1961 Ferrari Colombo engine in a Ferrari 250TR Spyder

In Europe, V12 engines were seen as excessive in the aftermath of World War II, therefore production of cars with V12 engines was very limited until the 1960s.

The 1948 Ferrari 166 Inter sports car (Ferrari's first road car) was powered by a 2.0 L (122 cu in) SOHC V12 engine. Lamborghini's first car, the 1964 Lamborghini 350 GT was powered by a 3.5 L (211 cu in) DOHC engine. These engines began long histories of V12 engines for the two Italian companies, which continue to the present day.

1971-1975 Jaguar V12 engine

1991-1997 Mercedes-Benz M120 engine

In Europe, several manufacturers added V12 engines to their line-up, as listed below:

• Jaguar: The Jaguar V12 engine was an all-aluminium SOHC design with displacements of 5.3–6.0 L (323–366 cu in) that was produced from 1971 to 1997. The first application for the engine was a 5.3 litre version used in the Jaguar E-Type sports car.[17][18][19]
• BMW: Production of V12 engines began with the BMW M70 SOHC engine introduced in the 1987 BMW 750iL luxury sedan. The engine was upgraded to a DOHC V12 engine in 2003, then to a turbocharged DOHC V12 engine which has been in production from 2008 to the present.[20][21][22] BMW V12 engines have also been used in several Rolls-Royce models, beginning in 1998 with the Rolls-Royce Silver Seraph.
• Mercedes-Benz: The company's first V12 engine was the Mercedes-Benz M120 engine, a 6.0 L (366 cu in) DOHC engine introduced in the 1991 Mercedes-Benz 600 SE luxury sedan. This engine was replaced by an SOHC V12 engine in 1998, then a turbocharged SOHC V12 engine which has been in production for 2003 to the present.[23] Mercedes-Benz V12 engines have also been used in several Maybach models, beginning with the Maybach 57 and 62 in 2002.
• Aston Martin: The 1999 Aston Martin DB7 V12 Vantage used the company's first V12 engine, a 5.9 L (362 cu in) DOHC design. This engine was replaced by a turbocharged DOHC V12 engine, which was introduced in the Aston Martin DB11 and has been produced from 2016 to the present.
• Audi: The 2008-2012 Audi Q7 SUV was powered by the Audi 6.0 V12 48v TDI engine, which was the first V12 diesel engine used in a production car.

In the United States, no mass-produced V12 engines have been built since the 1940s, with U.S. manufacturers preferring to use large displacement V8 engines instead.

Japanese manufacturers rarely produce engines with large displacements, therefore V12 engines are very rare. The sole Japanese V12 engine is the 1997-2016 Toyota GZ engine, a 5.0 L (305 cu in) SOHC design which was used in the Toyota Century limousine.[24][25]

In China, the 2009 Hongqi HQE limousine, powered by a 6.0 L (366 cu in) DOHC V12 engine, is the sole Chinese car to be produced with a V12 engine.[26]

V12 engines have often been used if Formula One, particularly during from the 1966 season to the 1969 season. The first V12 engine used in Formula One was in the 1964 Honda RA271 racing car, and continued through to the 1968 Honda RA301 racing car. The 1966 season saw V12 engines become popular, with new V12 engines from Ferrari, Maserati and Weslake. Ferrari's engine debuted in the Ferrari 312 racing car and was used up to the 1975 Ferrari 312B, after which Ferrari switched to a flat-twelve engine. Maserati's engine was introduced in the Cooper T81 and was used until the 1969 Cooper T86. The Weslake V12 engine was used from 1966-1968 and was introduced in the Eagle Mk1 racing car. BRM produced V12 engines from the 1968 BRM P133 racing car until the 1977 BRM P207. The Matra Sports V12 engine was introduced in the 1968 Matra MS11 racing car and used until the 1978 Ligier JS9. Few V12 engines were used in the following decade, with the exception of the Alfa Romeo V12 which was first used by the 1979 Brabham BT48 and used by Alfa Romeo until the 1982 Alfa Romeo 182.

A resurgence of V12 engines in Formula One began in 1989, with the introduction of the Ferrari 640 racing car. Ferrari continued to use V12 engines until the 1995 Ferrari 412 T2 became the last Formula One car to use a V12 engine. The Lamborghini LE3512 engine was used by various teams between 1989 and 1993. The Honda RA122-E engine was first used in the 1991 McLaren MP4/6 and was raced until the 1992 McLaren MP4/7A. The Yamaha OX99 engine was used in the 1990 Brabham BT59 through to the 1992 Brabham BT60.

In prototype sports car racing, the highly successful 2006-2008 Audi R10 TDI used a diesel twin-turbo V12 engine. The Peugeot 908 HDi FAP, introduced in 2007, also used a diesel twin-turbo V12 engine.

• Formula One engines
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  1989-1993 Lamborghini LE3512
• 
  1991 Honda RA121E
• 
  1968 Matra MS11