V6 engine

A V6 engine is a V engine with six cylinders mounted on the crankshaft in two banks of three cylinders, usually set at either a 60 or 90 degree angle to each other. The V6 is one of the most compact engine configurations, usually ranging from 2.0 L to 4.3 L displacement (however, much larger examples have been produced for use in trucks), shorter than the inline 4 and more compact than the V8 engine. Because of its short length, the V6 fits well in the widely used transverse engine front-wheel drive layout.

Applications

The V6 is commercially successful in mid-size cars in the modern age of high fuel prices and price sensitive consumers because it is less expensive to build and has better fuel consumption than the V8, while being smoother in large sizes than the inline 4, which develops increasingly serious vibration problems in larger engines. The wider 90° V6 will fit in an engine compartment designed for a V8, providing a low-cost alternative to the V8 in an expensive car, while the narrower 60° V6 will fit in most engine compartments designed for an I4, proving a more powerful and smoother alternative engine to the four. While not perfectly smooth, the V6 is smoother than the I4 and adequately smooth for the average consumer. Buyers of luxury and/or performance cars who are not price sensitive or fuel economy minded might prefer an inline 6, which has comparable fuel economy and power but better smoothness, a flat 6 which combines better smoothness and often higher power with adequate fuel economy, or a V8 which has higher power, but worse fuel economy.

Recent forced induction V6 engines have delivered horsepower and torque output comparable to contemporary larger displacement, naturally aspirated V8 engines, while reducing fuel consumption and emissions, such as the Volkswagen Group's 3.0 TFSI which is supercharged and directly injected, and Ford Motor Company's turbocharged and directly injected EcoBoost V6, both of which have been compared to Volkswagen's 4.2 V8 engine.^[1]

Modern V6 engines commonly range in displacement from 2.0 to 4.3 L (120 to 260 cu in), though larger and smaller examples have been produced, such as the 1991 Mazda MX3,^[2] and the Rover KV6 engine.

In Europe, where petrol is much more expensive than in the USA, V6 diesels have proved a more popular option. The American-designed Chrysler 300C has a 3-litre Mercedes V6 engine, which vastly outsells the petrol-engined car.

History

Some of the first V6-powered automobiles were built in 1905 by Marmon. This firm became something of a V-engine specialist; beginning with V2 engines, then V4s, V6s, V8s, and, in the 1930s, a V16 engine. Marmon was one of the few automakers of the world to offer a V16-powered automobile.^[3]

From 1908 to 1913 the Deutz Gasmotoren Fabrik produced gasoline-electric train sets (Hybrid) which used a V6 as generator engine.^[4]

In 1918 Leo Goosen designed a V6-powered car for Buick Chief Engineer Walter L. Marr. Only one prototype Buick V6 car was built in 1918; it was long used by the Marr family.^[5]

The first series-production V6 was introduced by Lancia in 1950 with the Lancia Aurelia model.^[6] Lancia sought a smoother and more powerful engine that would fit into an existing narrow engine bay. A Lancia engineer, Francesco De Virgilio, began analyzing the vibration of alternative V-angles for a V6 engine in 1943. He found that a V6 with its cylinders positioned at a 60° V-angle could be made uniquely smooth-running in comparison with other possible V-angles. There was resistance to his conclusion, because the V6 was a virtually unknown engine type in the 1950s. His design featured four main bearings and six crankpins, resulting in evenly spaced firing intervals and low vibrations.^[7]

Other manufacturers took note and soon other V6 engines were designed. In 1959, General Motors' GMC Truck division introduced a new 60-degree heavy-duty 305 in³ (5.0 L) gasoline-fueled 60° V6 for use in their pickup trucks and Suburbans; this engine design was later enlarged to 478 in³ (7.8 L) for heavy truck and bus use. The use of the sweet spot of 60 degrees' V-angle maximized power while minimizing vibration and exterior dimensions of the engine. In short, GMC introduced a compact V6 design at a time when the straight-six engine was considered the pinnacle of 6-cylinder design.^[8]

1962 saw the introduction of the Buick Special, which offered a new 90° V6 with uneven firing intervals that was derived from—and shared some parts commonality with—a small Buick V8 engine of the period. To save design time and expense, it was built much like a V8 that had two cylinders chopped off. The combination of a 90° V-angle with only three crank pins—set at 120° apart, with opposing cylinders sharing a crank pin as most V8 engines do—the cylinders fired alternatively at 90 and 150° of crankshaft rotation. This uneven firing caused harmonic vibrations in the drive train that were perceived as a rough-running engine by the buyers. GM sold the engine tooling to Kaiser-Jeep in 1967; later, as a result of the 1973 oil crisis, GM repurchased the tooling in 1974. In 1977, Buick introduced a split pin crankshaft to implement an even-fire version of this engine in which cylinders fired consistently every 120°.

Balance and smoothness

The V6 does not have the inherent freedom from vibration that the inline-six and flat-six have, but it can be modeled as two separate straight-3 engines sharing a crankshaft. Counterweights on the crankshaft and a counter rotating balance shaft are required to compensate for the first order rocking motions.

Straight engines with an odd number of cylinders are inherently unbalanced because there are always an odd number of pistons moving in one direction while a different number move the opposite direction. This causes an end-to-end rocking motion at crankshaft speed in a straight-three engine. V6 designs will behave like two unbalanced three-cylinder engines running on the same crankshaft unless steps are taken to mitigate it, for instance by using offset journals or flying arms on the crankshaft or a counter-rotating balance shaft.

In the straight-six engine layout, the two halves of the engine are mirror images of each other and the end-to-end rocking motions of each half become a bending moment which can be resisted by using a sufficiently stiff engine block. In the horizontally opposed flat-6 (an example being the "boxer"-type engine), layout the rocking motions of the two straight-three cylinder banks almost completely offset each other, except for a small moment caused by the fact that the cylinders must be offset slightly. This results in an engine which is short, light, and relatively smooth, but too wide for most engine compartments. It is widely used in light aircraft though, and in some automobile engines, by manufacturers such as Porsche and Subaru.

In the V6 with 120° between banks, pairs of connecting rods can share a single crank pin, but the two cylinder banks run like two inline 3, both having an end-to-end rocking couple. Unlike in a V8 engine with a crossplane crankshaft, the vibrations from one bank do not cancel the vibrations from the other, so a rotating balancing shaft is required to compensate for the primary vibrations. Because the 120° V6 is nearly as wide as a 180° flat-6 but is not nearly as smooth, and can be more expensive if a balancing shaft is added, this configuration is seldom seen in production engines.

In the V6 with 90° between cylinders, split crank pins are required to offset the connecting rods by 30° to achieve an even 120° between firing intervals, and crankshaft counterweights are required to offset the primary imbalances. In the 90° V6, a balancing shaft is desirable but not entirely necessary to minimize second-order vibrations, depending on the level of smoothness required. The main advantage of the 90° V6 is that it can easily be derived from an existing 90° V8 design, and use the same parts as the V8.

Unfortunately, a 90° V6 cannot use the same technique that balances an even firing 90° crossplane V8 engine; rotating the middle two cranks to 90° from the outer two, using extra-heavy counterweights on the crankshaft to offset the rocking motion, and then using the mass of the pistons in the other cylinder bank at 90° to counteract the side-to-side rotation that the heavy counterweights would otherwise cause (resulting in an engine that is in perfect primary and secondary balance, albeit one with very heavy crankshaft counterweights and uneven firing intervals into the exhaust headers, resulting in the familiar V8 "burbling" exhaust note).

A simple 90° V6 cannot achieve the same smoothness with only crankshaft counterweights, and if the 90° V6 uses shared crankpins like the V8, the engine will have uneven firing intervals, such as in the original "odd-fire" Buick V6 engine. This uneven firing interval results in roughness at idle and low RPM, and varying harmonics at higher engine speeds, making the "odd-fire" configuration unpopular with buyers, so most manufacturers now use split crankpins to make the firing intervals an even 120°. Therefore, designing a smooth V6 engine is a much more complicated problem than the straight-6, flat-6, and V8 layouts. Although the use of offset crankpins, counterweights, and flying arms has reduced the problem to a minor second-order vibration in modern designs, all V6s can benefit from the addition of auxiliary balance shafts to make them completely smooth.^[9]

When Lancia pioneered the 60° V6 in 1950, they used a 60° angle between the cylinder banks and a six-throw crankshaft to achieve equally spaced firing intervals of 120°. This still has some balance and secondary vibration problems. When Buick designed a 90° V6 based on their 90° V8, they initially used a simpler three-throw crankshaft laid out in the same manner as the V8 with pairs of connecting rods sharing the same crankpin, which resulted in firing intervals alternating between 90° and 150°. This produced a rough-running design which was unacceptable to many customers. Arguably, the roughness is in the exhaust note, rather than noticeable vibration, so the perceived smoothness is rather good at higher RPM. Later, Buick and other manufacturers refined the design by using a split-pin crankshaft which achieved a regular 120° firing interval by staggering adjacent crankpins by 15° in opposite directions to eliminate the uneven firing and make the engine reasonably smooth.^[10] Some manufacturers such as Buick in later versions of their V6 and Mercedes Benz have taken the 90° design a step further by adding a balancing shaft to offset the primary vibrations and produce an almost fully balanced engine.

Some designers have reverted to a 60° angle between cylinder banks, which produces a more compact engine, but have used three-throw crankshafts with flying arms between the crankpins of each throw to achieve even 120° angles between firing intervals. This has the additional advantage that the flying arms can be weighted for balancing purposes.^[10] This still leaves an unbalanced primary couple, which is offset by counterweights on the crankshaft and flywheel to leave a small secondary couple, which can be absorbed by carefully designed engine mounts.^[11]

Six-cylinder designs are also more suitable for larger displacement engines than four-cylinder ones because power strokes of pistons overlap. In a four-cylinder engine, only one piston is on a power stroke at any given time. Each piston comes to a complete stop and reverses direction before the next one starts its power stroke, which results in a gap between power strokes and annoying harshness, especially at lower revolutions. In a six-cylinder engine (other than odd-firing V6s), the next piston starts its power stroke 60° before the previous one finishes, which results in smoother delivery of power to the flywheel. In addition, because inertial forces are proportional to piston displacement, high-speed six-cylinder engines will suffer less stress and vibration per piston than an equal displacement engine with fewer cylinders.

Comparing engines on the dynamometer, a typical even-fire V6 shows instantaneous torque peaks of 150% above mean torque and valleys of 125% below mean torque, with a small amount of negative torque (engine torque reversals) between power strokes. On the other hand, a typical four-cylinder engine shows peaks of nearly 300% above mean torque and valleys of 200% below mean torque, with 100% negative torque being delivered between strokes.

In contrast, a V8 engine shows peaks of less than 100% above and valleys of less than 100% below mean torque, and torque never goes negative. The even-fire V6 thus ranks between the four and the V8, but closer to the V8, in smoothness of power delivery. An odd-fire V6, on the other hand, shows highly irregular torque variations of 200% above and 175% below mean torque, which is significantly worse than an even-fire V6, and in addition the power delivery shows large harmonic vibrations that have been known to destroy the dynamometer.^[12]

V angles

60 degrees

A V6 engine with a 60 degree included angle between cylinder banks hits the "sweet spot" in V6 engine design due to several desirable characteristics. Unlike most other V6 layouts, 60 degree engines can be made acceptably smooth without using a balance shaft. Although the engine will not be as smooth-running as an inline six or opposed six cylinder engine, modern design and mounting techniques can eliminate objectionable vibration.

In the 60 degree design, the connecting rods are attached to individual crankpins, which are angularly displaced at 120 degree intervals. This geometry results in an even firing interval, eliminating primary vibration and reducing secondary vibration to acceptable levels.

Lancia's pioneering design in 1950 utlized a six-throw crankshaft to achieve the required 120 degree angular displacement between crankpins. The GMC V6 engine, designed for commercial vehicles, also used a six-throw crankshaft, and was intentionally made physically massive in order to further dampen vibration, as well as to enhance durability. However, more recent designs often use a three-throw crankshaft with what are termed flying arms between the crankpins, which not only produce the required angular crankpin displacement, but also can be used for balancing purposes. Combined with a pair of heavy counterweights on the crankshaft ends, flying arms can eliminate all but a modest secondary imbalance, which can readily be dampened by the engine mounts.^[1]

The 60 degree design is one of the most compact engine layouts, being nearly a perfect cube that will fit longitudinally or transversely in most engine compartments. Hence the 60 degree configuration is a good fit in automobiles which are too large to be powered by four-cylinder engines, but in which compactness and low cost are important considerations. The most common 60 degree V6s were produced by General Motors (the aforementioned GMC commercial engine, as well as a design used in many GM front-wheel-drive automobiles) and Ford European subsidiaries (Essex V6, Cologne V6 and the more recent Duratec V6). Other 60 degree V6 engines are the Chrysler 3.3 engine, the Nissan VQ engine, the Mazda K engine, the Alfa Romeo V6 engine, the Mitsubishi 6G7 series of engines, many Toyota V6 engines and later versions of the Mercedes-Benz V6 engine.

90 degrees

Many manufacturers, particularly American ones, built V6 engines with an angle of 90 degrees because they already had a successful V8 and needed to create a smaller, lighter engine with better fuel economy to meet market demand. Such configurations were easy to design by removing two cylinders from an existing V8 engine design. In some cases, the first prototypes were created by simply sawing two cylinders out of a V8 engine, welding the block back together, and forging a 3-throw crankshaft to replace the V8 4-throw crank. This reduced design costs, allowed the new V6 to share components with the old V8, and sometimes allowed manufacturers to build V6s on the same production line as V8s.

Although it was relatively easy to create a 90° V6 by simply cutting two cylinders off an existing V8 engine, this produced an engine which was wider and more vibration-prone than a 60° V6. The design was first used by Buick when it introduced its 198 CID Fireball V6 as the standard engine in the 1962 Special. The Buick V6 was notable because it had uneven firing intervals between power strokes as a result of using the 90° cylinder bank angle and sharing crankpins between piston pairs as in the V8 engine. Rather than firing evenly every 120° of crankshaft rotation, the cylinders fired alternately at 90° and 150°, resulting in strong harmonic vibrations at certain engine speeds. These engines were often referred to by mechanics as "shakers", due to the tendency of the engine to vibrate at idle speed. Other examples included the Maserati V6 used in the Citroën SM, the PRV V6, the Rover KV6 (2.0- and 2.5-litre), the Honda C engine used in the NSX, Chevrolet's 4.3 L Vortec 4300 and Chrysler's 3.9 L (238 in³) Magnum V6 and 3.7 L (226 in³) PowerTech V6.

More modern 90° V6 engine designs avoid these vibration problems by using more sophisticated crankshafts with split crankpins offset by 30° between piston pairs to make the firing intervals an even 120°. They often add balancing shafts to eliminate the other vibration problems inherent in the layout. Examples include the later versions of the Buick V6, Chevrolet Vortec 4300, and earlier versions of the Mercedes-Benz V6. The 90° Mercedes V6, although it was designed to be built on the same assembly lines as the V8, used split crankpins, a counter-rotating balancing shaft, and careful acoustic design to make it almost as smooth as the inline-6 it replaced. However, in later versions Mercedes changed the cylinder banks to a 60° angle to make the engine more compact and eliminate the balancing shaft. Despite the difference in V angles, Mercedes modified its production lines so it could build 60° V6s on the same assembly lines as 90° V8s.^[13]

120 degrees

At first glance, 120° might be considered the natural angle for a V6 since pairs of pistons in alternate banks can share crank pins in a three-throw crankshaft, and the cylinders will fire evenly every 120° of crankshaft rotation. Unlike the 60° or 90° configurations, it does not require crankshafts with flying arms, split crankpins, or seven main bearings to be even-firing. This is equivalent to the 90° V8 in which cylinders fire every 90°. However, in the 120° V6 there is a primary dynamic imbalance caused by the fact there are an odd number of cylinders in each bank. At any given time in, each bank, two cylinders will be moving up while one moves down, and vice-versa. Each cylinder bank acts like a straight-3 and experiences a strong vibration at crankshaft speed.

By contrast, in the 90° V8 engine with a simple flat-plane crankshaft, each cylinder bank acts like a straight-4, which is much smoother than a straight-3. In addition, in 1915 the crossplane crankshaft was invented, which allowed the secondary vibrations from one cylinder bank of a V8 to cancel those from the other cylinder bank. This resulted in an almost perfectly smooth V8 engine which has been popular in luxury and sports cars since 1923.

Unfortunately, the crossplane crankshaft does not work for the V6. There is no way to arrange the 120° V6 so that unbalanced forces from the two cylinder banks will completely cancel each other. As a result, the 120° V6 acts like two straight-3s running on the same crankshaft and suffers from a primary dynamic vibration which requires a balance shaft to cancel. This has limited its use to trucks and racing cars where vibration is not as important as in passenger cars.

The 120° layout also produces an engine which is too wide for most automobile engine compartments, so it is more often used in racing cars where the car is designed around the engine rather than vice versa, and light weight and low center of gravity are major considerations. By comparison, the 180° flat-6 boxer engine is only moderately wider than the 120° V6, and is an almost fully balanced configuration with few vibration problems. It can be scaled up to very large and powerful configurations, so it has been commonly used in aircraft and in sports/luxury cars where space is not a constraint, but power and smoothness are important.

Spanish truck manufacturer Pegaso built the first production 120° V6 for the Z-207 midsize truck in 1955. The engine, a 7.5-litre alloy Diesel designed under the direction of engineer Wifredo Ricart uses a single balance shaft rotating at the speed of the crankshaft^[14]

Ferrari introduced a very successful 120° V6 racing engine in 1961. The Ferrari Dino 156 engine was shorter and lighter than the 65° Ferrari V6 engines that preceded it, and the simplicity and low center of gravity of the engine was an advantage in racing. It won a large number of Formula One races between 1961 and 1964. However, Enzo Ferrari had a personal dislike of the 120° V6 layout, preferring a 65° angle, and after that time it was replaced by other engines.^[15]

Bombardier designed 120° V220/V300T V6 engines for use in light aircraft. A balance shaft on the bottom of the engine offset the primary dynamic imbalance. However, it was costly, the market was small, and it had no overwhelming advantages over the 180° flat-6 engines already in common use in light planes. The design was shelved in 2006 and there are no plans for production.^[16]

Narrow angle VR6

Volkswagen's VR6 engines are a family of V6 engines characterized by extremely narrow-angle (10.5° or 15°) V configurations. These engines were developed by the manufacturer in the late 1980s for transverse engine installations in its front-wheel drive vehicles, which were originally designed for straight-4 engines. The wider configuration of a wider angle V6 engine would have required an extensive redesign of the vehicles to enlarge the engine compartment. The narrow angle of 15° (and later 10.5°) between the two cylinder banks in the VR6 engine made it much narrower than other V6 designs. The VR6 engine is only moderately longer and wider than a straight-4 engine but has 50% greater engine displacement. This made it possible to install more powerful six-cylinder engines in existing four-cylinder cars.^[17]

The VR6 engine is also smoother than most V6s without balance shafts. It uses a firing order of 1,5,3,6,2,4 similar to a straight-6 rather than a more typical V6 firing order like 1,2,3,4,5,6. In terms of balance and smoothness the VR6 acts more like a staggered-cylinder straight-6 rather than a conventional V6.

The narrow angle between cylinders allows the use of just one cylinder head that covers both cylinder banks, whereas wider angle V engines require two separate cylinder heads, one for each cylinder bank. The VR6 arrangement has "twin SOHC" valve gear operating the 24 valves via rocker arms; it is NOT a true DOHC design. This simplifies engine construction and reduces costs. Since there is no room in the V between the cylinder banks for an intake system, all the intakes are on one side of the engine, and all the exhausts are on the other side.^[17] This system is efficient and simplifies installation into the engine compartment.

The Volkswagen VR6 was originally designed as a 2.8 litre engine, but some versions have been built as large as 3.6 litres in size. In addition to Volkswagen, VR6 engines have also been used by Audi and Porsche, although Audi also uses its own designs of wider-angle V6s. Some other manufacturers have also used VR6 engines in their vehicles.

Other angles

Other angle V6 engines are possible but can suffer from severe vibration problems unless very carefully designed. Notable V6 bank angles include:

• The 45° Electro-Motive 6-, 8-, 12-, 16- and 20-cylinder versions of their 567 Series, 645 Series and 710 Series locomotive, marine and stationary Diesel engines. This angle is optimum for the more common 8- and 16-cylinder versions. In all of these engines, directly opposite cylinders always fire 45 degrees apart, so engines other than 8- and 16-cylinder versions are uneven firing. 6-cylinder engines were only made in the 567 and 645 Series; 20-cylinder engines were only made in the 645 and 710 Series.
• The 54° GM/Opel V6, designed to be narrower than normal for use in small front-wheel drive cars.
• The 65° Ferrari Dino V6, allowing larger carburetors (for potentially higher power in race tuning) than a 60° angle and having crankpins with a 115 degree offset to get the same level of vibration as in a 60 degree V6, while having an even firing order.
• The 65° Renault V6 diesel named V9X, has a 65° bank angle for easier installation of turbocharger inside the vee
• The 72° Mercedes-Benz Bluetec Diesel V6 utilizes a counter-rotating balance shaft and crankpins offset by 48° to eliminate vibration problems and make the engine even-firing.
• The 75° Isuzu V engine used in the Isuzu Rodeo and Isuzu Trooper of 3.2 and 3.5 L in both SOHC and DOHC versions. Honda also introduced a 75° V6 engine in the second generation Honda NSX.
• The 80° Honda RA168-E Formula One engine in the McLaren MP4/4.

Odd and even firing

Many older V6 engines were based on V8 engine designs, in which a pair of cylinders was cut off the front of V8 without altering the V angle or using a more sophisticated crankshaft to even out the firing interval. Most V8 engines share a common crankpin between opposite cylinders in each bank, and a 90° V8 crankshaft has just four pins shared by eight cylinders, with two pistons per crankpin, allowing a cylinder to fire every 90° to achieve smooth operation.

Early 90° V6 engines derived from V8 engines had three shared crankpins arranged at 120° from each other. Since the cylinder banks were arranged at 90° to each other, this resulted in a firing pattern with groups of two cylinders separated by 90° of rotation, and groups separated by 150° of rotation, causing a notorious odd-firing behavior, with cylinders firing at alternating 90° and 150° intervals. The uneven firing intervals resulted in rough-running engines with unpleasant harmonic vibrations at certain engine speeds.

An example is the Buick 231 odd-fire, which has a firing order 1-6-5-4-3-2. As the crankshaft is rotated through the 720° required for all cylinders to fire, the following events occur on 30° boundaries:

Angle	0°									90°									180°									270°									360°									450°									540°									630°
Odd firing	1															6									5															4									3															2
Even firing	1												4												5												6												3												2

More modern 90° V6 engines avoid this problem by using split crankpins, with adjacent crankpins offset by 15° in opposite directions to achieve an even 120° ignition pattern. Such a 'split' crankpin is weaker than a straight one, but modern metallurgical techniques can produce a crankshaft that is adequately strong.

In 1977, Buick introduced the new "split-pin crankshaft" in the 231. Using a crankpin that is 'split' and offset by 30° of rotation resulted in smooth, even firing every 120°. However, in 1978 Chevrolet introduced a 90° 200/229 V6, which had a compromise 'semi-even firing' design using a crankpin that was offset by only 18°. This resulted in cylinders firing at 108° and 132°, which had the advantage of reducing vibrations to a more acceptable level and did not require strengthening the crankshaft. In 1985, Chevrolet's 4.3 (later the Vortec 4300) changed it to a true even-firing V6 with a 30° offset, requiring larger crank journals to make them adequately strong.

In 1986, the similarly designed 90° PRV engine adopted the same 30° crankshaft offset design to even out its firing. In 1988, Buick introduced a V6 engine that not only had split crankpins, but had a counter-rotating balancing shaft between the cylinder banks to eliminate almost all primary and secondary vibrations, resulting in a very smooth-running engine.

Racing use

The V6 engine was introduced into racing by Lancia in the early 1950s. After good results with privately entered Aurelia saloons Lancia set a works competition department in 1951. Four B20 Coupes were entered in the '51 Mille Miglia and the one driven by Giovanni Bracco and Umberto Maglioli caused quite a stir by finishing second overally after the 4.1-litre Ferrari driven by Villoresi and Cassani, a car which had three times more power than the Lancia. After that encouraging start Lancia decided to carry on with the endurance racing program, first with specially prepared Aurelias (called Da Corsa) and then with specially built prototypes. A D24 with a 3,102 cc (189 cu in) V6 making 230 PS (170 kW) won the 1953 Carrera Panamericana with Juan Manuel Fangio at the wheel.

After that came the Ferrari Dino V6. Alfredo Ferrari (nicknamed Dino), son of Enzo Ferrari, suggested to him the development of a 1.5 L DOHC V6 engine for Formula Two at the end of 1955. The Dino V6 underwent several evolutions, including an increased engine displacement to 2,417 cc (147 cu in), for use in the Ferrari 246 Formula One car in 1958.^[18][19]

The use of a wide 120° bank angle is appealing for racing engine designers as it permits a low center of gravity. This design is even considered superior to the flat-6 in that it leaves more space under the engine for exhaust pipes; thus the crankshaft can be placed lower in the car. The Ferrari 156 built for new Formula One 1.5 L regulations used a Dino V6 engine with this configuration.^[20]

The Dino V6 engine saw a new evolution in 1966 when it was adapted to road use and produced by a Ferrari-Fiat joint-venture for the Fiat Dino and Dino 206 GT (this car was made by Ferrari but sold under the brand Dino). This new version was redesigned by Aurelio Lampredi initially as a 65° 2.0 L (120 cu in) V6 with an aluminum block but was replaced in 1969 by a 2.4 L (150 cu in) cast-iron block version (the Dino car was renamed the 246GT).

The Fiat Dino and Dino 246GT were phased out in 1974, but 500 engines among the last built were delivered to Lancia, who was like Ferrari already under the control of Fiat. Lancia used them for the Lancia Stratos which would become one of the most successful rally cars of the decade.

The Alfa Romeo V6 was designed in the 1970s by Giuseppe Busso, the first car to use them being the Alfa Romeo 6. The over-square V6, with aluminium alloy block and heads, has seen continuous use in road vehicles, from the Alfetta GTV6 onwards. The 164 introduced a 3.0 L (180 cu in) V6, a 2.0 V6 turbocharged in 1991 and in 1992, a 3.0 L DOHC 24-valve version. The Alfa 156 introduced a 2.5 L DOHC 24-valve version in 1997. The engine capacity was later increased to 3.2 L (200 cu in), where it found application in the 156 GTA, 147 GTA, 166, GT, GTV and Spider 916. Production was discontinued in 2005.

A notable racing use of the V6 engine was the Alfa Romeo 155 V6 TI, designed for the 1993 Deutsche Tourenwagen Meisterschaft season and equipped with a 2.5 L (150 cu in) engine making a peak power of 490 PS (360 kW; 480 hp) at 11,900 rpm.

Another influential V6 design was the Renault-Gordini CH1 V6, designed by François Castaing and Jean-Pierre Boudy, and introduced in 1973 in the Alpine-Renault A440. The CH1 was a 90° cast-iron-block V6, similar to the mass-produced PRV engine in those two respects but otherwise dissimilar. It has been suggested that marketing purposes made the Renault-Gordini V6 adopt those characteristics of the PRV in the hope of associating the two in the public's mind.

Despite such considerations, this engine won the European 2 L prototype championship in 1974 and several European Formula Two titles. This engine was further developed in a turbocharged 2 L version that competed in Sports car and finally won the 24 Hours of Le Mans in 1978 with a Renault-Alpine A 442 chassis.

The capacity of this engine was reduced to 1.5 L to power the Formula One Renault RS01. Despite frequent breakdowns that resulted in the nickname of the 'Little Yellow Teapot', the 1.5 L finally saw good results in 1979.

Ferrari followed Renault in the turbo revolution by introducing a turbocharged derivative of the Dino design (a 1.5 L 120° V6) with the Ferrari 126.^[21] However, the 120° design was not considered optimal for the wing cars of the era and later engines used V angles of 90° or less.

Both Renault and Ferrari failed in their attempt to win the Drivers' Championship with V6 Turbo engines. The first turbocharged engine to win the championship was the Straight-4 BMW.

They were followed by a new generation of Formula One engines, the most successful of these being the TAG V6 (designed by Porsche) and the Honda V6. This new generation of engines were characterized by odd V angles (around 80°). The choice of these angles was mainly driven by aerodynamic consideration. Despite their unbalanced designs these engines were both quickly reliable and competitive; this is generally viewed as a consequence of the quick progress of CAD techniques in that era.

In 1989 Shelby tried to bring back the Can-Am series, using the Chrysler 3.3 L (201 cu in) V6 (not yet offered to the general public) as the powerplant in a special racing configuration making 255 hp (190 kW). This was the same year that the Viper concept was shown to the public.

Originally the plan was to produce two versions of this race car, a 255 hp (190 kW) version and a 500 hp (370 kW) model, the 255 hp (190 kW) version being the entry circuit. The cars were designed to be a cheap way for more people to enter auto racing. Since all the cars were identical, the winners were to be the people with the best talent, not the team with the biggest pockets. The engines had Shelby seals on them and could only be repaired by Shelby's shop, ensuring that all the engines are mechanically identical.

Only 100 of these 3.3s were ever built. Of these 100, 76 were put into Shelby Can-Am cars (the only 76 that were ever sold). No significant amount of spare parts were produced, and the unsold engines were used for parts/spares. The Shelby specific parts, such as the upper intake manifold, were never made available to the general public. According to a small article in the USA Today (in 1989), these cars were making 250 hp (190 kW) (stock versions introduced in 1990 produced 150 hp or 110 kW) and hitting 160 mph (260 km/h) on the track. The engine itself was not that far from a standard-production 3.3. The Shelby engine is only making about 50 hp (37 kW) more than the newest 3.3 factory engines from Chrysler. The Can-Am engine has a special Shelby Dodge upper intake manifold, a special Shelby Dodge throttle body, and a special version of the Mopar 3.3 PCM (which had this engine redlining at 6800 rpm).

Nissan also has a quite successful history of using V6's for racing in both IMSA and the JGTC. Development of their V6s for sports cars began in the early 1980s with the VG engine initially used in the Z31 300ZX. The engine began life as a SOHC, turbocharged 3.0L power plant with electronic fuel injection, delivering 230 PS (169 kW). The VG30ET was later revised into the VG30DETT for the Z32 300ZX in 1989. The VG30DETT sported both an additional turbocharger and an extra pair of camshafts, making the engine a genuine DOHC twin-turbo V6 producing 300 PS (221 kW). Nissan used both of these engines in its AIMS racing program throughout the 1980s and 1990s each producing well over 800 hp (600 kW). In the Japan Grand Touring Car Championship, or JGTC, Nissan opted for a turbocharged version of its VQ30 making upwards of 500 hp (370 kW) to compete in the GT500 class.

V6 turbos have been used in the IndyCar Series since 2012, with Chevrolet and Honda currently supplying the engines. Lotus also made engines in the 2012 season, but pulled out at the end of the year.

The 2014 Formula One season included the return of the V6 engine to Formula One, in the form of a regulation mandated, turbocharged 1.6L 90° hybrid engine. This engine integrates the combustion engine with a (mandated maximum output) 161 bhp (120 kW) 'motor generator unit' electric motor system consisting of a 'motor generator unit - kinetic' component, which is the electric motor itself, capable of energy recovery through regenerative braking and a 'motor generator unit - heat' component, which is a similar system integrated into the turbocharging system, to allow the elimination of turbolag and additional system charging through the turbocharger once the turbine system is kept up at speed by exhaust gasses.

Motorcycle use

Laverda showed a 996 cc V6-engined motorcycle at the 1977 Milan show.^[22] The motorcycle was raced in the 1978 Bol d'Or.

Marine use

V6 engines are popular powerplants in medium to large outboard motors.

Notes

References

• Borgeson, Griffith (1998). The Golden Age of the American Racing Car (2nd ed.). Society of Automotive Engineers. ISBN 0-7680-0023-8. 
• Box, Rob De La Rive (1998). The Complete Encyclopedia of Vintage Cars 1886 - 1940 (3rd ed.). Rebo Productions. ISBN 90-366-1517-8. 
• Kane, Jack (2006). Torsional Output of Piston Engines. Aircraft Engine Technology. 2006 Advanced Engine Technology Conference (AETC): EPI, Inc. Retrieved 2008-01-14. 
• Ludvigsen, Karl (2001). Classic Racing Engines. Haynes Publishing. ISBN 978-1-85960-649-0. 
• Matschoss, Conrad (1921). Geschichte der Gasmotorenfabrik Deutz. Berlin. 
• Nunney, M J (2007). Light and Heavy Vehicle Technology (4th ed.). Butterworth-Heinemann. ISBN 0-7506-8037-7. 

External links

Wikimedia Commons has media related to V6 automobile engines.

• AutoZine Technical School - V6 Engines
• 60-66 GMC Truck Club Celebrating the Legendary GMC V6 Engine - V6 Engines