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.
Since each cylinder bank is essentially a straight-6, this configuration has perfect primary and secondary balance no matter which V angle is used and therefore needs no balance shafts. A V12 with two banks of six cylinders angled at 60°, 120° or 180° (with the latter configuration usually referred to as a flat-12) from each other has even firing with power pulses delivered twice as often per revolution as a straight-6. This allows for great refinement in a luxury car. In a racing car, the rotating parts can be made much lighter and thus more responsive, since there is no need to use counterweights on the crankshaft Template:Examples Template:Citation needed as is needed in a 90° V8 and less need for the inertial mass in a flywheel to smooth out the power delivery. In a large displacement, heavy-duty engine, a V12 can run slower than smaller engines, prolonging engine life.
The first V12 engines were used in aircraft. By the end of World War I, V12s were popular in the newest and largest fighters and bombers and were produced by companies such as Renault and Sunbeam. Many Zeppelins had 12-cylinder engines from German manufacturers Maybach and Daimler. Various U.S. companies produced the Liberty L-12; the Curtiss NC Flying boats, including the four V12 engine powered NC-4, the first aircraft to make a transatlantic flight.
V12 engines reached their apogee during World War II. Fighters and bombers used V12 engines such as the British Rolls-Royce Merlin and Griffon, the Soviet Klimov VK-107, the American Allison V-1710, or the German Daimler-Benz DB 600 series and Junkers-Jumo. These engines generated about 1,000 hp (750 kW) at the beginning of the war and above 1,500 hp (1,100 kW) at their ultimate evolution stage. The German DB 605D engine reached 2,000 hp (1,500 kW) with water injection. In contrast to most Allied V12s, the engines built in Germany by Daimler-Benz, Junkers-Jumo, and Argus (As 410 and As 411) were primarily inverted, which had the advantages of lower centers of gravity and improved visibility for single-engined designs. Only the pre-war origin BMW VI V12 of Germany was an "upright" engine. The United States had the experimental Continental IV-1430 inverted V12 engine under development, with a higher power-to-weight ratio than any of the initial versions of the German WW II inverted V12s, but was never developed to production status, with only 23 examples of the Continental inverted V12 ever being built.
The Rolls-Royce Merlin V12 powered the Hawker Hurricane and Supermarine Spitfire fighters that played a vital role in Britain's victory 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. The Merlin was also used in the Avro Lancaster and de Havilland Mosquito bombers. In the United States the Packard Motor company was licensed by Rolls-Royce to produce the Merlin as the Packard V-1650 for use in the North American P-51 Mustang. It 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 only indigenous U.S.-developed V12 liquid-cooled engine to see service during World War II. A sturdy design, it lacked an advanced mechanical supercharger until 1943. Although versions with a turbosupercharger provided excellent performance at high altitude in the Lockheed P-38 Lightning, the turbosupercharger and its ductwork were too bulky to fit into typical single-engine fighters. While a good performer at low altitudes, without adequate supercharging, the Allison's high-altitude performance was lacking.
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 in large aircraft.
 V12 road cars
In automobiles, V12 engines have not been common due to their complexity and cost. They are used almost exclusively in expensive sports cars and luxury cars because of their power, smoother operation, and distinctive sound.
Until the general adoption of vibration isolating engine mounts in the 1930s, vehicles with 8-, 12-, and 16-cylinders provided higher levels of refinement.
Packard's 1916 "Twin Six" is widely regarded as the first production V12 engine. With a list price of US$1,000, the Auburn was the lowest priced V12 car ever (unadjusted for inflation). Production cost savings were achieved by using horizontal valves, which did not make for an efficient and powerful combustion chamber. Between 1916 and 1921, there was a vogue of V12s, during which National (Indianapolis) copied the Packard engine,Template:Citation needed and Weidely Motors (also of Indianapolis) offered a proprietary engine. Soon after the end of World War I, Lancia offered a 22° V12, Fiat had a 60° model 520 (1921-2), British truck manufacturer Ensign announced a V12 that did not materialize, and in 1926, Daimler (Britain) offered the first of a full range of sleeve valve Double Sixes, 7,136 cc, 3,744 cc, 5,296 cc and 6,511 cc versions remaining available until 1937. In 1927 more entered the market from, Cadillac, Franklin, Hispano-Suiza, Horch, Lagonda, Maybach, Packard, Rolls, Tatra, Voisin, and Walter offering V12 engines. Cadillac (from 1930 to 1940) and Marmon (1931–1933) even developed V16 engines.
Improvements in combustion chamber design and piston form enabled lighter V8 engines to surpass the V12 in power starting from the 1930s; only the smaller, H-Series Lincoln V-12 remained after WWII and it was replaced by a V8 in 1949. Similarly, as they seemed excessive for the postwar market in Europe, production of V12-engined-cars was very limited until the 1960s.
Ferrari has traditionally reserved their top V12 engine for their top-of-the line luxury sports coupes since 1949. Ferrari's closest rival, Lamborghini has also used the V12 configuration for many of its road cars since the company's inception in 1963. In 1972, Jaguar came out with the XJ12, equipped with a 5.3 litre V12, which continued (after revisions in 1993) until the 1996 model year, after which the marque discontinued the twelve-cylinder engine.
German manufacturer BMW returned to V12 designs for its 7-Series sedan in model year 1986, forcing Mercedes-Benz to follow suit in 1991. While BMW sells far fewer V12-engined 7-Series vehicles than V8 versions, the V12 retains popularity in the US, China, and Russia, as well as maintaining the marque's prestige in the luxury vehicle market segment. The BMW-designed V12 also appears in Rolls-Royce cars, while the Mercedes engine is also seen in Maybach cars. In their full-sized sedans sold in Canada and the USA, Mercedes and BMW have mid-displacement V8s for the entry-level trims, while having the V12 as the flagship vehicle of the brand. For their most expensive Mercedes-Benz nameplates (S-Class, CL-Class, and SL-Class), there are V8-engined AMG models (55, 63) that have comparable power to their V12-powered cars (600).
TVR made and tested a 7.7 L V12 called the Speed Twelve, but the project was scrapped after the car it was designed for was deemed too powerful for practical use. The only British marques currently using a V12 configuration are Aston Martin — whose Cosworth-developed engine was authorized during the company's ownership by Ford Motor Company — and Rolls-Royce.
 Postwar V12 production cars
This is a list of V12-engined production road cars, sorted alphabetically by make (and sub-sorted by year of introduction):
- Aston Martin DB7 Vantage
- Aston Martin Vanquish
- Aston Martin DB AR1
- Aston Martin DB9
- Aston Martin DBS
- Aston Martin V12 Vantage
- Aston Martin One-77
- Aston Martin Rapide
- Audi Q7
- B Engineering Edonis
- BMW 750i/750iL/760i/760Li
- BMW 850i/Ci/CSi
- Bugatti EB110
- Daimler Double Six
- Ferrari 125
- Ferrari 166
- Ferrari 195
- Ferrari 212
- Ferrari 340/342/375/375 America
- Ferrari 250
- Ferrari 410 Superamerica & 400 Superamerica
- Ferrari 275
- Ferrari 330
- Ferrari 500 Superfast
- Ferrari 365 California
- Ferrari 365 GT 2+2
- Ferrari 365 GTC & GTS
- Ferrari 365 GTB/4 & 365 GTS/4 "Daytona"
- Ferrari 365 GTC/4
- Ferrari 365 GT4 2+2
- Ferrari 400, 400i & 412
- Ferrari 456
- Ferrari F50
- Ferrari 550 Maranello & 550 Barchetta Pininfarina
- Ferrari 575M Maranello & 575M Superamerica
- Ferrari Enzo
- Ferrari 612 Scaglietti
- Ferrari 599 GTB Fiorano/GTO
- Ferrari FF
- Ferrari F12 Berlinetta
- Hongqi HQE
- Jaguar E-Type V12
- Jaguar XJ-S
- Jaguar XJ12 & XJ12C
- Jaguar XJR15
- Lamborghini 350GT
- Lamborghini 400GT
- Lamborghini Islero
- Lamborghini Miura
- Lamborghini Espada
- Lamborghini Jarama
- Lamborghini Countach
- Lamborghini LM002
- Lamborghini Diablo
- Lamborghini Murciélago
- Lamborghini Reventón
- Lamborghini Aventador
- Lincoln Continental
- Lister Storm
- Lotec Sirus
- Maserati MC12
- Maybach 57 and 62
- McLaren F1
- Mercedes-Benz CL600/CL63 AMG (W215 only)/CL65 AMG
- Mercedes-Benz S600/S63 AMG (W220 only)/S65 AMG
- Mercedes-Benz SL600/SL65 AMG/SL70 AMG (R129)/SL73 AMG (R129)
- Mercedes-Benz CLK GTR AMG
- Pagani Zonda
- Pagani Huayra
- Panther De Ville
- Panther J72
- Rolls-Royce Silver Seraph/Silver Seraph Park Ward
- Rolls-Royce Phantom
- Rolls-Royce Phantom Drophead Coupé
- Rolls-Royce Phantom Coupé
- Rolls-Royce Ghost
- Toyota Century
- Tramontana R
- Vector M12
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 Prototypes/custom made with V12 engines
- Audi R8 Le Mans Concept
- BMW Nazca M12 (a concept by Pininfarina)
- BMW CS Concept
- Bertone Genesis
- Cadillac Cien
- Ferrari FXX (cannot be used on the road)
- Ferrari P540 Superfast Aperta
- Ford GT90
- Ford Indigo
- Isdera Commendatore 112i
- Jaguar XJ13
- Jaguar XJ220 Concept
- Lamborghini Flying Star II
- Lamborghini LM004
- Laraki Fulgura
- Lincoln Continental (2002 concept)
- Maybach Exelero
- Méga Monte Carlo
- Peugeot 907 (Peugeot's first V12, 2004)
- Toyota Century Royal
- TVR Cerbera Speed Twelve (never entered production)
- Volga V12 Coupe (a one-off custom rebody)
- Yamaha OX99-11
- Zagato Raptor
 Heavy trucks
Tatra used a 17.6 L (1,070 cu in) air-cooled naturally aspirated V12 diesel engine in many of their trucks; for instance, the Tatra T813 and uses 19 L air-cooled naturally aspirated or turbo V12 diesel engine in Tatra T815. Some trucks have been fitted with twin V12s, although this is often advertised as a V24.
GMC produced a large gasoline-burning V12 from 1960 to 1965 for trucks, the "Twin-Six"; it was basically GMC's large-capacity truck 351 V6, doubled, with four rocker covers and four exhaust manifolds. Fifty-six major parts are interchangeable between the Twin-Six and all other GMC V6 engines to provide greater parts availability and standardization. Its engine displacement was 702 cu in (11.50 L), and while power was not too impressive at 250 hp (190 kW), torque was 585 lb·ft (793 N·m). For firetrucks the rev limiter was increased to produce 299 hp (223 kW) at 3000 rpm and torque was increased to 630 lb·ft (850 N·m) at 1600-1900 rpm. It was possibly the last gasoline engine used in heavy trucks in the U.S.
Detroit Diesel produced their Series 53, 71, 92, and 149 engines as V-12s, among other configurations.
 Auto racing
V12 engines used to be common in Formula One and endurance racing. From 1965 to 1980, Ferrari, Weslake, Honda, BRM, Maserati, Matra, Delahaye, Peugeot, Delage, Alfa Romeo, Lamborghini and Tecno used 12-cylinder engines in Formula One, either V12 or Flat-12, but the Ford (Cosworth) V8 had a slightly better power-to-weight ratio and less fuel consumption,Template:Citation needed thus it was more successful despite being less powerful than the best V12s. During the same era, V12 engines were superior to V8s in endurance racing, reduced vibrations giving better reliability.Template:Citation needed In the 1990s, Renault V10 engines proved their superiority against the Ferrari and Honda V12s and the Ford V8. The last V12 engine used in Formula One was the Ferrari 044, on the Ferrari 412T2 cars driven by Jean Alesi and Gerhard Berger in 1995.
At the Paris motor show 2006 Peugeot presented a new racing car, as well as a luxury saloon concept car, both called 908 HDi FAP and 908 RC and fitted with a V12 Diesel engine producing around or even surpassing 700 PS (515 kW; 690 hp). This took part in the 24 Hours of Le Mans 2007 race, with a podium finish and very competitive performance, coming in second place after the similarly conceived Audi R10 TDI V12 Diesel originally developed for the 2006 season.
 Large diesel engines
V12 is a common configuration for large diesel engines; most are available with differing numbers of cylinders in V configuration to offer a range of power ratings. Many diesel locomotives have V12 engines. Examples include the 3,200 hp (2.39 MW) 12-710 from Electro-Motive Diesel and the 4,400 hp (3.28 MW) GEVO-12 from GE Transportation.
Large V12 engines are also common in ships. For example Wärtsilä, the world's leading manufacturers of medium-speed diesel engines, offers V12 engines with various cylinder bore diameters between 26 and 50 centimetres (10 and 20 in) with power output ranging from 4,080 kW (5,470 hp) to 14,400 kW (19,300 hp). These engines are commonly used especially in cruise ships, which may have up to six such main engines. In the past the largest medium-speed diesel engine in the world, Wärtsilä 64, was also offered in V configuration, and a single 12V64 prototype with an output of 23,280 kW (31,220 hp) was produced for an experimental power plant in the late 1990s.
 Tanks and other AFVs
The V12 is a common configuration for tank and other armoured fighting vehicles (AFVs). Some examples are:
- German Maybach HL120TRM gasoline engine, used on World War II Pz Kpfw III and Pz Kpfw IV tanks.
- British Rolls-Royce Meteor gasoline engine, derived from the Merlin aero-engine, used on World War II Cromwell and Comet tanks and the post-WWII Centurion and Conqueror tanks.
- Russian V-2 (В-2) V-12 diesel engine, used on World War II T-34, KV-1, KV-2 and IS-2 tanks. Most modern Russian diesel engines for MBT's goes back to V-2 base design.
- American Continental AV1790 engine, produced in gasoline and diesel variants, used on all versions of the Patton tank and on the M103 heavy tank. One of these engines was used to power a hot rod style car called the Blastolene Special.
- ↑ Nunney, Malcolm James (2007). Light and Heavy Vehicle Technology (4 ed.). Butterworth-Heinemann. pp. 13–14. ISBN 9780750680370.
- ↑ Georgano, G.N. (2002). Cars: Early and Vintage, 1886-1930. Mason Crest. ISBN 9781590844915.
- ↑ Georgano.
- ↑ "2010 BMW 760i / 760Li - First Drive Review - Auto Reviews". Car and Driver. July 2009. http://www.caranddriver.com/reviews/car/09q3/2010_bmw_760i_760li-first_drive_review. Retrieved 2011-09-29.
- ↑ "First Drive: 2010 Mercedes-Benz S400 Hybrid". Nationalpost.com. http://www.nationalpost.com/cars/story.html?id=2237320. Retrieved 2010-07-01.
- ↑ Mort, Norm (2010). American Trucks of the 1960s. Veloce Publishing. pp. 41–44. ISBN 9781845842284. http://books.google.com/books?id=lM_mr0ihODcC&pg=PA42&dq=GMC+twin+six+702&hl=en. Retrieved 6 October 2010.
- ↑ Medium-speed engines. Wärtsilä. Retrieved on 2011-10-22.
- ↑ Diesels offer hot Competition. Power Engineering International, 1 September 1998.