1 : V12
2 : Aviation
3 : V12 road cars
4 : Heavy trucks
5 : Auto racing
6 : Large diesel engines
7 : External links
A V12 is an internal combustion engine with 12 cylinders in V configuration. When the two banks of six cylinders are angled at 60° from each other, this configuration has perfect primary and secondary balance, like a straight-6, but with power pulses delivered twice as often per revolution it is much smoother. 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 less need for the inertial mass in a flywheel to smooth out the power delivery. In a large, heavy-duty engine, a V12 can run slower than smaller engines, prolonging engine life.
V12 engines were first seen in aircraft. By the end of World War I, the V12 configuration was a fairly popular one in the newest and largest fighters and bombers; V12 engines were produced by companies such as Renault and Sunbeam, and various US companies produced the V12 liberty engine. Many Zeppelins had V12 engines, from German manufacturers Maybach and Daimler.
A number of World War II fighters and bombers used V12 engines such as the Rolls-Royce Merlin engine or the Allison V-1710, usually generating about 1,500 horsepower (1 MW). Their use disappeared quickly after the advent of the jet engine.
V12 road cars
In automobiles, V12 engines have never been common, because of their complexity and thus cost. Their use has been thus confined to costly luxury and sports cars, in which they give superlative performance and smoothness characteristics.
Prior to World War II, twelve-cylinder engines were found in many luxury models, including cars from Cadillac, Packard, Lincoln, Rolls-Royce and Hispano-Suiza.
Postwar, the type lost favor in the United States, where the V8 became ubiquitous. Italian sports cars from such makers as Lamborghini and Ferrari used the V12 almost exclusively on their highest-performance vehicles, while Jaguar developed a V12 that was put into production in 1971 and lasted until 1997.
In the early 1990s, the German manufacturers Mercedes-Benz and BMW both introduced V12 designs. The BMW-designed V12 also appears in Rolls-Royce cars, while the Mercedes engine is also seen in Maybach cars. Aston Martin introduced a V12 model in 2001, while Cadillac are re-introducing the V12 after 60 years with a V12 version of their Northstar engine range. This engine is to be available initially only in the Cadillac Escalade luxury SUV.
Tatra uses a 17.6 litre air-cooled turbo diesel V12 engine in many of their trucks, for instance the Tatra T813 and Tatra T815. Some trucks have been fitted with twin V12s.
GMC produced a large gasoline-burning V12 in the 1960s for trucks, the "Twin-Six"; it was basically GMC's large-capacity truck V6, doubled, with four cam covers and four exhaust manifolds. Its displacement was 702 cubic inches (11.5 litres), and while power wasn't too impressive at 250 SAE net horsepower (190 kW), torque was an impressive 585 lb-ft (793 Nm). It was possibly the last gasoline engine used in heavy trucks in the United States.
They used to be common in Formula One and Endurance racing. Between 1965 and 1980 Ferrari, Weslake, Honda, BRM, Maserati, Matra, Alfa-Romeo and Tecno have used 12 cylinders in Formula One, either V12 or Flat-12, but the Ford Cosworth V8 had slightly better power-to-weight ratio and less fuel consumption, thus it was more successful despite being less powerful than the best V12. During the same era V12 engines where superior to V8 in Endurance racing, reduced vibrations giving better reliability. In the 1990s the Renault V10 engines proved their superiority against the Ferrari and Honda V12 and the Ford V8. Now all Formula One cars use V10 engines.
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.
Mercedes (MTU) manufacture a line of V12 diesel engines for marine use. These engines commonly power craft up to about 100 tons in pairwise configurations and range in power from about 1 to 4 MW.