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.

Aviation

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 at the beginning of the war and above at their ultimate evolution stage. The German DB 605D engine reached 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 exceptional 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 US-developed V-12 liquid-cooled engine to see service during World War II. A sturdy and trustworthy design, it unfortunately lacked an advanced mechanical supercharger until 1943. Although versions with a turbosupercharger did give 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 superb 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, which 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 and are sought after for their power, smoother operation, and distinctive sound.

Prior to World War II, 12-cylinder engines were found in many luxury models, including cars from Auburn, Cadillac, Daimler, Packard, Lincoln, Franklin, Rolls-Royce, Pierce-Arrow, and Hispano-Suiza.

Until the general adoption of vibration isolating engine mounts in the 1930s, 8 12 and 16 cylinder cars provided important 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. 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, 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, 7,136cc, 3,744cc, 5,296cc and 6,511cc 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 1930–1940) 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).

In 1997, Toyota equipped their Century Limousine with a 5.0 L DOHC V12 (model # 1GZ-FE), making it the first and only Japanese production passenger car so equipped.

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.

In 2009, China FAW Group Corporation equipped their Hongqi HQE with a 6.0 L DOHC V12 (model # CA12VG), making it the first and only Chinese production passenger car so equipped.

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):

Some tuner companies, such as Brabus also sell V12 versions of the Mercedes-Benz E-Class and CLS, which were the fastest street-legal sedans upon their respective introductions.

Prototypes/custom made with V12 engines

Heavy trucks

Tatra used a 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.

GMC produced a large gasoline-burning V12 from 1960-1965 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 V-6 engines to provide greater parts availability and standardization Its engine displacement was , and while power was not too impressive at , torque was . For firetrucks the Rev limiter was increased to produce at 3000 RPM and torque was increased to 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

In the late 1960s Nissan used a V12 in the Japanese Grand Prix and again in the early 1990s Group C races.

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 . 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 12-710 from Electro-Motive Diesel and the GEVO-12 from GE Transportation.

Mercedes (MTU) manufactured a line of V12 diesel engines for marine use. These engines commonly power craft up to about 100 tonnes in pairwise configurations and range in power from about .

Tanks and other AFVs

V12 is a common configuration for tank and other armoured fighting vehicles (AFVs). Some examples are:

References

External links