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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 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 V-type engine (a 2-cylinder vee twin) was built in 1889 by Daimler, to a design by Wilhelm Maybach. By 1903 V8 engines were being produced for motor boat racing by the Société Antoinette to designs by Léon Levavasseur, building on experience gained with in-line four-cylinder engines. In response, in 1904 the Putney Motor Works completed a new V12 marine racing engine – the first V12 engine produced for any purpose. Known as the ‘Craig-Dörwald’ engine after Putney’s founding partners, the engine mounted pairs of L-head cylinders at a 90 degree included angle on an aluminium crankcase, using the same cylinder pairs that powered the company’s standard 2-cylinder car. A single camshaft mounted in the central vee operated the valves directly. As in many marine engines the camshaft could be slid longitudinally to engage a second set of cams, giving valve timing that reversed the engine’s rotation to achieve astern propulsion.
Displacing 18,345 cc (bore and stroke of 123.8 x 127 mm), the engine weighed 950 pounds (430 kg) and developed 150 bhp (110 kW). Little is known of the engine's achievements in the 40-foot hull for which it was intended, while a scheme to use the engine to power heavy freight vehicles never came to fruition.
Two more V12s appeared in the 1909-10 motor boat racing season. The Lamb Boat & Engine Company of Clinton, Iowa built a 25,560 cc (133.4 x 152.4 mm) engine for the company’s 32-foot Lamb IV. It weighed in at 2,114 pounds (959 kg). No weight is known for the massive 56,758 cc (177.8 x 190.5 mm) F-head engine built by the Orleans Motor Company. Output is quoted as “nearly400 bhp (300 kW)”.
In October 1913 Louis Coatalen, chief engineer of the Sunbeam car company entered a V12 powered car in the Brooklands short and long handicap races. The engine displaced 9,048 cc, with bore and stroke of 80 x 150 mm. An aluminium crankcase carried two blocks of three cylinders along each side, with a 60 degree included angle. The cylinders were of iron, with integral cylinder heads with L-shaped combustion chambers. Inlet and exhaust valves were operated by a central camshaft in the vee. Valve clearance was set by grinding the relevant parts, the engine lacking any easy means of adjustment. This pointed to Coatalen’s ultimate aim of using the new V12 as an aero engine, where any adjustment method that could go wrong in flight was to be avoided. As initially built the V12 was rated at 200 bhp (150 kW) at 2,400 rpm, weighing about 750 pounds (340 kg). The engine powered the car (named ‘Toodles V’ (for Coatalen’s wife Olive’s pet name) to several records in 1913 and 1914.
In 1909 Renault pioneered aero V12s with a 60 degree air-cooled engine with individual finned cylinders and F-head valve arrangement, driven by single camshaft in the crankcase. This was developed to a 12,160 cc unit (96 x 140 mm) which weighed 772 pounds (350 kg) and produced 138 bhp (103 kW) at 1,800 rpm. The propeller was driven from the nose of the camshaft in the central vee, rather than from the crankshaft, thus providing an automatic half-speed reduction, improving propeller efficiency.
Renault’s designs were closely followed in Britain by the Royal Aircraft Factory. Its RAF 4 engine displaced 13,195 cc (100 x 140 mm), produced 140 bhp (100 kW) at 1,800 rpm, for a weight of 637 pounds (289 kg). Its RAF 4a derivative was produced in substantial numbers during the war.
In March 1914 Sunbeam exhibited an airborne version of Toodles V’s engine at Olympia. Racing in 1913 had helped to prove the design, and encouraged a 10 mm increase in bore to 90 m, the stroke remaining at 150 mm. Its rated output was 225 bhp (168 kW) at 2,000 rpm. Named the ‘Mohawk’, the engine was the most powerful available to British aviation at the outbreak of WW1. During the war further enlargement to 100 x 150 mm created the 240 bhp (180 kW) ‘Gurkha’.
By the end of World War I, V12s were well established in aviation, powering some of the newest and largest fighters and bombers and being 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. Soon after the end of WW1 V12 engines powered the first trans-atlantic crossings by the Curtiss NC Flying boats (4 x Liberty L-12), the first non-stop crossing by Alcock and Brown in a Vickers Vimy (2 x Rolls-Royce Eagles and the first airship crossing by HM airship R-34 (5 x Sunbeam Maori).
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.
In automobiles, V12 engines have not been common due to their complexity and cost. They are used almost exclusively in expensive sports and luxury cars because of their power, smoother operation and distinctive sound.
Prior to World War II, 12-cylinder engines were found in many luxury models, including cars from: Packard 1916 to 1923, Daimler 1926 to 1937, Hispano-Suiza 1931, Cadillac 1931, Auburn 1932, Franklin 1932, Lincoln 1932, Rolls-Royce 1936, and Pierce-Arrow also 1936.
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, however, did not result in an efficient and powerful combustion chamber. Between 1916 and 1921, there was a vogue of V12s, during which National (Indianapolis) copied the Packard engine, 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.
Most production V12 engines in road cars have an even firing order, with the uneven-firing exceptions such as Aston Martin 5.9L V12 and Mercedes-Benz M275 AMG V12s.
This is a list of V12-engined production road cars, sorted alphabetically by make (and sub-sorted by year of introduction):
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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 large trucks have been fitted with twin V12s that drive a common shaft, 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.
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, 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. 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.
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, 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.
The V12 is a common configuration for tank and other armoured fighting vehicles (AFVs). Some examples are:
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