A straight-six engine (also referred to as an inline-six engine; abbreviated I6 or L6) is a
piston engine
A reciprocating engine, more often known as a piston engine, is a heat engine that uses one or more Reciprocating motion, reciprocating pistons to convert high temperature and high pressure into a Circular motion, rotating motion. This article ...
with six cylinders arranged in a straight line along the
crankshaft
A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...
. A straight-six engine has perfect primary and secondary
engine balance
Engine balance refers to how the inertial forces produced by moving parts in an internal combustion engine or steam engine are neutralised with counterweights and Balance shaft#Overview, balance shafts, to prevent unpleasant and potentially dam ...
, resulting in fewer vibrations than other designs of six or fewer cylinders.
Until the mid-20th century, the straight-six layout was the most common design for engines with six cylinders. However,
V6 engine
A V6 engine is a six- cylinder piston engine where the cylinders and cylinder blocks share a common crankshaft and are arranged in a V configuration.
The first V6 engines were designed and produced independently by Marmon Motor Car Company, ...
s gradually became more common in the 1970s and by the 2000s, V6 engines had replaced straight-six engines in most light automotive applications.
Characteristics
In terms of packaging, straight-six engines are almost always narrower than a
V6 engine
A V6 engine is a six- cylinder piston engine where the cylinders and cylinder blocks share a common crankshaft and are arranged in a V configuration.
The first V6 engines were designed and produced independently by Marmon Motor Car Company, ...
or
V8 engine
A V8 engine is an eight- cylinder piston engine in which two banks of four cylinders share a common crankshaft and are arranged in a V configuration.
Origins
The first known V8 was the Antoinette, designed by Léon Levavasseur, a ...
, but longer than
straight-four engine
A straight-four engine (also referred to as an inline-four engine) is a four-cylinder Reciprocating engine, piston engine where cylinders are arranged in a line along a common crankshaft.
The majority of automotive four-cylinder engines use a ...
s, V6s, and most V8s. Compared to V-configuration engines with similar power and displacement, the straight configuration has fewer injectors, a single head, and a single exhaust manifold, all contributing to better reliability and performance.
Straight-six engines are typically produced in displacements ranging from , however engines range in size from the
Benelli 750 Sei
The Benelli Sei is a series of motorcycles that were produced by Italian manufacturer Benelli (motorcycles), Benelli, and masterminded by automotive designer Alejandro de Tomaso, from 1973 to 1989.Benelli 750/900 Performance Portfolio 1973-1989. R. ...
motorcycle engine to the
Wärtsilä-Sulzer RTA96-C
The Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is designed for large container ships that run on heavy fuel oil. Its largest 14-cylinder version is high, lo ...
two-stroke marine diesel engine. Due to its well-balanced configuration, the straight-six can be scaled up to substantial sizes for heavy trucks, locomotives, industrial and marine use.. When two straight-six engines are mated with a common crankshaft it forms a
V12 engine
A V12 engine is a twelve-Cylinder (engine), cylinder Internal combustion engine#Reciprocating engines, piston engine where two banks of six cylinders are arranged in a V engine, V configuration around a common crankshaft. V12 engines are more c ...
.
Engine balance and vibration
If an appropriate
firing order
The firing order of an internal combustion engine is the sequence of ignition for the cylinders.
In a spark ignition (e.g. gasoline/petrol) engine, the firing order corresponds to the order in which the spark plugs are operated. In a diesel engi ...
is used, a straight-six engine has perfect primary and secondary
engine balance
Engine balance refers to how the inertial forces produced by moving parts in an internal combustion engine or steam engine are neutralised with counterweights and Balance shaft#Overview, balance shafts, to prevent unpleasant and potentially dam ...
. The primary balance is due to the front and rear trio of cylinders moving in pairs (albeit 360° out of phase), thus canceling out the rocking motion present in a
straight-three engine
A straight-three engine (also called an inline-triple or inline-three) is a three-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.
Less common than straight-four engine, straight-three engines have nonethel ...
. The secondary balance is due to the crank throws being arranged in three planes offset at 120°, resulting in the non-sinusoidal forces summing to zero for all free forces until the sixth order.
The engine balance characteristics of a straight-six engine compare favorably with the more common
straight-four engine
A straight-four engine (also referred to as an inline-four engine) is a four-cylinder Reciprocating engine, piston engine where cylinders are arranged in a line along a common crankshaft.
The majority of automotive four-cylinder engines use a ...
s,
V6 engine
A V6 engine is a six- cylinder piston engine where the cylinders and cylinder blocks share a common crankshaft and are arranged in a V configuration.
The first V6 engines were designed and produced independently by Marmon Motor Car Company, ...
s, and
V8 engine
A V8 engine is an eight- cylinder piston engine in which two banks of four cylinders share a common crankshaft and are arranged in a V configuration.
Origins
The first known V8 was the Antoinette, designed by Léon Levavasseur, a ...
s which experience significant secondary dynamic imbalance, resulting in engine vibration. As engine reciprocating forces increase with the cube of piston bore, the straight-six is a preferred configuration for large truck and industrial engines.
Two-stroke engines
An even-firing six-cylinder
two-stroke
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston, one up and one down, in one revolution of the crankshaft in contrast to a four-stroke engine which re ...
engine requires ignitions at 60° intervals, or else it would run with simultaneous ignitions and be no smoother than a
triple
Triple is used in several contexts to mean "threefold" or a " treble":
Sports
* Triple (baseball), a three-base hit
* A basketball three-point field goal
* A figure skating jump with three rotations
* In bowling terms, three strikes in a row
* I ...
in power delivery. As such, it also requires crank throws at 60°. Such designs appear to have been limited to diesel engines such as the Detroit 71 series, marine engines, and outboard motors.
Some of the 120 possible crankshaft configurations have useful properties. Still, all of them have a rocking imbalance that may or may not require a balance shaft, depending on the application. The six pistons with six unique phases cannot be "paired" as in the four-stroke case. The Detroit engines used a configuration that, once the primary
rocking couple
In physics, a couple or torque is a pair of forces that are equal in magnitude but opposite in their direction of action. A couple produce a pure rotational motion without any translational form.
Simple couple
The simplest kind of couple consi ...
was balanced out, was also perfectly balanced at all other rocking couples until the 6th order. Mercury came to use a configuration that canceled only the primary rocking couple and was run without a balancer.
The reciprocating masses of all configurations are still imbalanced at only 6th-order and up in their plane of motion. Still, the balance of kinetic energy exchange between pistons has improved to a residual 6th-order-and-up inertial torque oscillation compared with the four-stroke design being imbalanced at 3rd-order and up.
Crankshaft
Crankshaft
A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...
s for straight-six engines usually have either four
main bearing
A main bearing is a bearing in a piston engine which holds the crankshaft in place and allows it to rotate within the engine block.
The number of main bearings per engine varies between engines, often in accordance with the forces produced b ...
s (i.e., a bearing in between each pair of
crankpin
A crankpin or crank pin, also known as a rod bearing journal, is a mechanical device in an engine which connects the crankshaft to the connecting rod for each cylinder. It has a cylindrical surface, to allow the crankpin to rotate relative to th ...
s and one at each end) or seven main bearings (i.e., a bearing between every crankpin):
* Large displacement and diesel engines typically use seven bearings to minimize crankshaft flex. When an engine is subject to high loads at low speeds, the greater distance between main bearings causes increased crankshaft flex. Modern high-compression engines subject the crankshaft to greater bending loads from higher peak gas pressures, requiring the crank throws to have more significant support from adjacent bearings. So, it is common for straight-six engines to use seven main bearings.
* Smaller and high-performance engines typically use four bearings since having fewer main journals decreases friction and increases the torsional stiffness of the crankshaft. The lack of torsional stiffness can make the seven main bearing designs susceptible to torsional flex and potential breakage at high engine speeds. Any torsional flex in the crankshaft is compounded by the torsional flex of the
camshaft
A camshaft is a shaft that contains a row of pointed cams in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition syst ...
s for the rear cylinders since the camshafts are rather long and subject to torsional flex. At high engine speeds, the combination of camshaft and crankshaft flex results in inaccurate timing of the valve openings, which, in the worst case, can cause the valves and pistons to collide with catastrophic results.
Usage in cars
The first production straight-six engine was introduced in the
Dutch
Dutch or Nederlands commonly refers to:
* Something of, from, or related to the Netherlands
** Dutch people as an ethnic group ()
** Dutch nationality law, history and regulations of Dutch citizenship ()
** Dutch language ()
* In specific terms, i ...
''
Spyker
Spyker or Spijker was a Dutch carriage, automobile and aircraft manufacturer, started in 1880 by blacksmiths Jacobus and Hendrik-Jan Spijker. Originally located in Hilversum, the company relocated to Trompenburg, Amsterdam in 1898.
Notable produ ...
60 HP'' racing car in 1903. Straight-six engines increased in popularity in the years after and by 1909, approximately 80 manufacturers were using them (including 62 in the United Kingdom). Prior to the 1950s,
V6 engine
A V6 engine is a six- cylinder piston engine where the cylinders and cylinder blocks share a common crankshaft and are arranged in a V configuration.
The first V6 engines were designed and produced independently by Marmon Motor Car Company, ...
s were rarely used, due to the poorer
engine balance
Engine balance refers to how the inertial forces produced by moving parts in an internal combustion engine or steam engine are neutralised with counterweights and Balance shaft#Overview, balance shafts, to prevent unpleasant and potentially dam ...
of V6 engines compared to straight-six engines. Since the 1980s, however, the shorter length of V6 engines has seen most manufacturers replace straight-six engines with V6 engines. An exception to this trend is the German brand
BMW
Bayerische Motoren Werke AG, trading as BMW Group (commonly abbreviated to BMW (), sometimes anglicised as Bavarian Motor Works), is a German multinational manufacturer of vehicles and motorcycles headquartered in Munich, Bavaria, Germany. Th ...
, which has always used a straight-six layout for its six-cylinder engines.
Since 2017, the trend of switching to V6 engines has reversed due to the ability to create a modular engine family of straight engines sharing many components. Examples include the 2017–present
Mercedes-Benz M256 engine
The Mercedes-Benz M256 engine is a turbocharged straight-six engine produced since 2017, when it was first introduced on the W222 S 450. It replaces the previous M276 V6 engine, and is Mercedes' first straight-six engine since the M104 engine.
...
Stellantis Hurricane engine
The Chrysler Hurricane GME-T6 engine is a twin-turbocharged straight-six engine produced by Chrysler(now Stellantis North America) since November 2021 at their plant in Saltillo, Mexico, and announced publicly in March 2022. It had been in develo ...
Skyactiv-D
Skyactiv (styled SKYACTIV) is a brand name for a series of automobile technologies developed by Mazda that increase fuel efficiency and engine output. The initial announcement of the Skyactiv technologies included new engines, transmissions, body ...
engines.
Europe
Alfa Romeo's first production straight-six engine - 6.3 L flathead petrol engine - was introduced in 1921 in the Alfa Romeo G1 luxury car. An
overhead valve
An overhead valve engine, abbreviated (OHV) and sometimes called a pushrod engine, is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with flathead (or "sidevalve") engines, where the v ...
design was introduced in the 1922
Alfa Romeo RL
The Alfa Romeo RL was produced between 1922 and 1927. It was Alfa's first sport model after World War I, designed in 1921 by Giuseppe Merosi. It had a straight-6 engine with overhead valves, and came in three different versions: Normale, Turismo a ...
sports car, and an
overhead camshaft
An overhead camshaft (OHC) engine is a piston engine in which the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustio ...
design was used in the 1927
Alfa Romeo 6C
The Alfa Romeo 6C name was used on road, race, and sports cars produced between 1927 and 1954 by Alfa Romeo; the "6C" name refers to the six cylinders of the car's straight-six engine. Bodies for these cars were made by coachbuilders such as Jam ...
sports car and various racing cars from 1927 until 1954. The last Alfa Romeo model using a straight-six was the 1961–1969
Alfa Romeo 2600
The Alfa Romeo 2600 (Tipo 106) was Alfa Romeo´s six-cylinder flagship produced from 1962 to 1968. It was the successor to the Alfa Romeo 2000. It has become historically significant as the last Alfa Romeo to have been fitted with a straight-six e ...
executive car before the company switched to V6 engines.
Mercedes-Benz's history of straight-six engines began with the 1913 Mercedes D.I aircraft engine. The first automotive straight-six engine was the 1924–1929 ''Daimler M836'' 3.9 L petrol engine. Following World War 2, Mercedes resumed production of straight-six engines with the 1951 introduction of the Mercedes-Benz M180 overhead camshaft engine. In 1985, the
Mercedes-Benz OM603
The OM603 engine was a straight-6 Diesel automobile engine from Mercedes-Benz used from 1984 through 1999. The 603 saw limited use in the W124
The Mercedes-Benz W124 is a range of executive cars made by Daimler-Benz from 1984 to 1997. The ran ...
3.0 L diesel straight-six engine was introduced. In 1996, the company replaced its petrol straight-sixes with a series of V6 engines, although it continued producing diesel straight-six engines. Production of petrol straight-six engines resumed in 2017 with the introduction of the Mercedes-Benz M256 turbocharged DOHC engine.
Opel began production of straight-six engines in 1927 with a 1.8 L flathead petrol engine used by the Opel 8/40 PS. The displacement of this engine was expanded as it was used in later models such as the
Opel Kapitän
The Opel Kapitän is a luxury car made in several different generations by the German car manufacturer Opel from 1938 until 1970.
Kapitän (1938–1940)
The Kapitän was the last new Opel model to appear before the outbreak of the Second Wo ...
and Opel Admiral, with later versions switching to an overhead valve (pushrod) design. In 1968, the straight-six versions of the
Opel CIH engine
The Opel cam-in-head engine (CIH) is a family of automobile engines built by former General Motors subsidiary Opel from 1965 until 1998, appearing extensively in Opel/Vauxhall badged cars during this period. Both four- and six-cylinder inline conf ...
were introduced, initially using a single overhead camshaft (SOHC) with some later versions using double overhead camshafts (DOHC). Production of the Opel CIH engine continued until 1993, when a V6 engine replaced it.
Volvo began production of straight-six engines with the 1929–1958
Penta DB
Penta DB was an engine model produced by Volvo Penta, AB Pentaverken. The 1929 introduced engine was a Flathead engine, side-valve engine with a cast-iron block and seven main bearings, and the first straight-six engine used in Volvos. Four other ...
flathead petrol engines. The company resumed production in 1969 with the Volvo B30 overhead valve petrol engine, followed by the straight-six versions of the
Volvo Modular Engine
The Volvo Modular Engine is a family of straight-four, straight-five, and straight-six automobile piston engines that was produced by Volvo Cars in Skövde, Sweden from 1990 until 2016. All engines feature an aluminium engine block and aluminium ...
introduced in 1995 and then the
Volvo SI6 engine
The SI6 (Short Inline 6) is a family of straight-six engines developed by Volvo and used by Land Rover and Volvo.
History
Volvo designed the SI6 ("short inline 6") straight-six automobile engine for use in 2007 models. An evolution of the company ...
introduced in 2006. Several models (such as the 1998–2006
Volvo S80
The Volvo S80 is an executive car produced by the Swedish manufacturer Volvo Cars from 1998 to 2016 across two generations. It took the place of the rear-wheel-drive S90 as Volvo's flagship sedan.
The first generation (1998–2006) was made a ...
) used the uncommon design of a transversely-mounted straight-six engine. Production of Volvo straight-six engines ceased in 2015.
BMW's first product was the 1917
BMW IIIa
BMW IIIa was an inline six-cylinder SOHC valvetrain, water-cooled aircraft engine, the first-ever engine produced by Bayerische Motoren Werke AG, who, at the time, were exclusively an aircraft engine manufacturer. Its success laid the foundati ...
straight-six aircraft engine. The company began production of automotive straight-six engines in 1933 with the BMW M78 petrol engine, a 1.2 L overhead valve design that evolved over the years into the BMW M337 (produced until 1958). Production of straight-six engines resumed in 1968 with the
BMW M30
The BMW M30 is a SOHC straight-six petrol engine which was produced from 1968 to 1995. With a production run of 27 years, it is BMW's longest produced engine and was used in many car models.
The first models to use the M30 engine were the BMW 25 ...
single overhead camshaft engine, built for 27 years and used in various models. The 1978–1989
BMW M88
The BMW M88 is a straight-6 DOHC petrol engine which was produced from 1978 to 1989. It is based on the DOHC version of the BMW M49 engine, which was used in the BMW 3.0CSi racing cars.
The M88 was produced alongside the BMW M30 engine, as the ...
engine was a double overhead camshaft design that was introduced in the
BMW M1
The BMW M1 (model code E26) is a Mid-engine design, mid-engined sports car produced by German automotive manufacturer BMW from 1978 until 1981.
In the late 1970s, Italian automobile manufacturer Lamborghini entered into an agreement with BMW to ...
mid-engine sport car. BMW's introduction of turbocharged straight-six engines (aside from the low-volume variants of the M30 engine in the 1980s) was in 2006
BMW N54
The BMW N54 is a twin-turbocharged straight-six petrol engine that was produced from 2006 to 2016. It is BMW's first mass-produced turbocharged petrol engine and BMW's first turbocharged petrol engine since the limited-production BMW M106 was disc ...
and the production of naturally aspirated engines ceased in 2015. , the
BMW B58
The BMW B58 is a Turbocharger, turbocharged straight-six engine, which began production in 2015. The B58 replaced the BMW N55, N55 and was launched in the BMW F30, F30 340i.
The B58 is part of BMW's modular engine family, each engine using a disp ...
turbocharged straight-six engine remains in production, along with its higher performance
BMW S58
The BMW B58 is a turbocharged straight-six engine, which began production in 2015. The B58 replaced the N55 and was launched in the F30 340i.
The B58 is part of BMW's modular engine family, each engine using a displacement of per cylinder, fol ...
variants.
United Kingdom
Rolls-Royce's first straight-six engine was a 6.0 L IOE petrol engine, which was used in the 1905
Rolls-Royce 30 hp
The Rolls-Royce 30 hp was one of four cars to be produced as a result of an agreement of 23 December 1904 between Charles Rolls and Henry Royce. Badged as a Rolls-Royce, the 30 hp was produced during 1905 and 1906 by Royce's company, ...
luxury car. This car was replaced by the 1906–1926
Rolls-Royce Silver Ghost
The Rolls-Royce Silver Ghost name refers both to a car model and one specific car from that series. Originally named the "Tax horsepower#Britain, 40/50 h.p." the chassis was first made at Royce's Manchester works, with production moving t ...
, which switched to a flathead (side-valve) design for its straight-six engine.
In 1906, the ''
Standard Standard may refer to:
Symbols
* Colours, standards and guidons, kinds of military signs
* Standard (emblem), a type of a large symbol or emblem used for identification
Norms, conventions or requirements
* Standard (metrology), an object ...
Six'' luxury car was introduced, powered by a I6 petrol engine. Standard's engines were also used in several cars built by SS Cars and its successor Jaguar, such as the 1932
SS 1
The SS 1 (the top of its radiator says 'SS One') is a British two-door sports saloon and tourer built by Swallow Sidecar Company, Swallow Coachbuilding Company in Foleshill, Coventry, England. It was first presented to the public at the 1931 ...
sports car, the 1936
SS Jaguar 100
The SS Jaguar 100 is a British 2-seat sports car built between 1936 and 1939 by SS Cars Ltd of Coventry, England. The manufacturer's name 'SS Cars' used from 1934 maintained a link to the previous owner, Swallow Sidecar Company, Swallow Sidec ...
and the 1938 Jaguar 3½ Litre sports saloon/coupe and the 1948
Jaguar Mark V
The Jaguar Mark V (pronounced ''mark five'') is a luxury automobile built by Jaguar Cars Ltd of Coventry in England from 1948 to 1951. It was available as a four-door Saloon (sedan) and a two-door convertible known as the Drop Head Coupé, both ...
luxury car.
The 1927
Rover Two-litre
The Rover Two-litre was a mid-size luxury open tourer, saloon or limousine produced from 1927 by the Rover Company of Coventry and available through to 1932. The chassis was also available to coach builders.
The 16 hp Two-litre was supp ...
luxury car introduced the company's IOE straight-six petrol engine. This engine was used in various Rover models until the
Rover P5
The Rover P5 is a series of large sedan (car), saloon and coupé cars that were produced by Rover (car), Rover from 1958 until 1973. The models were marketed under the names Rover 3 Litre, Rover 3.5 Litre and Rover 3½ Litre.
The P5 was a lar ...
was discontinued in 1973, and in various Land Rover models from the 1961 Land Rover Series IIA until 1980 Land Rover Series III.
The 1928 Austin 20/6 luxury car introduced Austin's flathead straight-six petrol engine. The 1938-1939 Austin Twenty-Eight used an enlarged version of this engine. This was replaced by the Austin D-Series engine, an overhead valve engine initially designed for trucks, which was used in passenger cars from 1947 until 1968 (along with several
Jensen Motors
Jensen Motors Limited was a England, British manufacturer of sports cars and commercial vehicles in West Bromwich, England. Brothers Alan and Richard Jensen gave the new name, Jensen Motors Limited, to the commercial- and sports car body-making ...
models from 1946 to 1962). The overhead valve BMC C-Series was used by various BMC brands from 1954 to 1971, followed by the 2.2 L version of the BMC E-Series overhead camshaft engine, which was produced from 1970 until 1982.
The 1930–1936
Wolseley Hornet six
The Wolseley Hornet is a six-cylinder twelve fiscal horsepower lightweight automobile which was offered as a saloon car, coupé and open two-seater as well as the usual rolling chassis for bespoke coachwork. Produced by Wolseley Motors, Wolseley ...
lightweight car was powered by a 1.3-1.6 L overhead camshaft straight-six petrol engine.
The 1931–1932
MG F-type
The MG F-type Magna is a six-cylinder-engined car that was produced by MG from October 1931 to 1932. It was also known as the 12/70.
Looking for a car to fill the gap between the M-Type Midget and the 18/80, MG turned to another of the engi ...
tourers, 1932–1934
MG K-type
The MG K-type Magnette is a motor car produced in the United Kingdom by MG from October 1932 to 1934.
Launched at the 1932 London Motor Show, the K-Type replaced the F-Type Magna but having at first a slightly smaller capacity engine it took ...
sports cars, and 1934–1936
MG N-type
The MG N-type Magnette is a sports car that was produced by MG (car), MG from October 1934 to 1936. The car was developed from the MG K-type, K-Type and MG L-type, L-Type but had a new chassis that broke away in design from the simple ladder typ ...
sports cars were powered by an overhead camshaft straight-six petrol engine.
During the mid-1930s, the
Riley MPH
The Riley MPH is a small production, two-seat sports car made between 1934 and 1935 by the Riley company of Coventry, England. Very few were made, and examples are now highly sought after.
The chassis, with half-elliptic springs and rigid axles ...
sports car and ''Riley Kestrel 6'' saloon were produced in small numbers and were powered by dual overhead camshaft straight-six petrol engine.
The 1947 Bristol 400 luxury car was powered by an overhead valve straight-six petrol engine based on the design of the BMW M328 engine. This engine remained in use until the
Bristol 406
The Bristol 406 was a luxury car produced between 1958 and 1961 by British manufacturer Bristol Aeroplane Co. Their cars were constructed to very high engineering standards and were intended to be long-lasting to justify their very high price. ...
was discontinued in 1961.
The dual overhead camshaft
Jaguar XK6 engine
The Jaguar XK is an inline 6-cylinder dual overhead camshaft (DOHC) engine produced by Jaguar Cars between 1949 and 1992. Introduced as a 3.4-litre, it earned fame on both the road and track, being produced in five hemispherical head di ...
petrol engine was produced from 1948 to 1992 in the
Jaguar XK120
The Jaguar XK120 is a sports car manufactured by Jaguar between 1948 and 1954. It was Jaguar's first sports car since SS 100 production ended in 1939. The XK120 was launched in open two-seater or (US) roadster form at the 1948 London Motor Sho ...
sports car. Introduced as a 3.4 L, it was used in passenger and racing cars, produced in displacements of 2.4 to 4.2 L. The XK6 engine was followed by the AJ6 and AJ16 engines, produced from 1984 to 1996, before being replaced by a Ford-derived V6 engine.
The 1948–1959 Lagonda straight-6 dual overhead camshaft petrol engine was used in various Aston Martin and Lagonda cars. This engine's successor was the Tadek Marek-designed straight-six used in the DB4 (1958), DB5 (1963), DB6 (1965) and DBS (1967).
The Ford Zephyr 6 overhead valve engine was used in the ''Ford Zephyr'' executive car and several other models from 1951 to 1966.
The Triumph I6 overhead valve straight-six petrol engine was produced from 1960 to 1977 and debuted in the Standard Vanguard Six sports saloon. The Leyland PE166 engine was loosely based on the Triumph design and was produced from 1977 to 1986.
The 1972–1977 TVR 2500M sports car was powered by the Triumph I6 engine. Then, from 1999 to 2007, TVR's own
TVR Speed Six
The TVR Speed Six was the name of a naturally aspirated straight-six engine manufactured from 1999 to 2007 by British car manufacturer TVR, and used in several of their cars including the Tuscan, Cerbera, Tamora, T350, Sagaris and Typhon.
...
dual overhead camshaft engine was used in several of the company's sports cars.
United States
The 1906–1908
Ford Model K
The Ford Model K is an upscale automobile that was produced by Ford Motor Company. Introduced in 1906, the “K” replaced the earlier Model B. It was built at the Ford Piquette Avenue Plant. The Model K was aimed at the top end of the market ...
luxury car used a straight-six petrol engine and was the only Ford six-cylinder passenger car engine until the 1940s. The Ford flathead I6 was produced from 1941 until 1951, followed by the Ford OHV I6 overhead valve engine from 1952 through 1964, then the Ford Thriftpower Six overhead valve engine from 1960 until 1982, and the Ford 240 I6 from 1965 through 1972. The Ford version of the straight-six engine was built from 1965 until 1996, with notable uses in trucks, SUVs, and vans. However, Ford straight-sixes were replaced by V6 engines in passenger cars during the mid-1970s.
In 1908, the Oldsmobile Model Z was powered by a flathead straight-six petrol engine, which was produced until 1912 (in the
Oldsmobile Limited
The Oldsmobile Limited was a top-level passenger car produced by GM's Oldsmobile Division in 1910, offered as an upgraded replacement to the Oldsmobile Model Z when it was discontinued in 1909. The Oldsmobile Limited was very large and expensive ...
luxury car) in displacements of , and . Oldsmobile's next straight-six engine was introduced in the 1913 Oldsmobile Six luxury car, initially with a displacement of , followed by a displacement of for the 1917-1921 Oldsmobile Model 37 luxury car. The later generations of the Oldsmobile Straight-6 also used a flathead design from its introduction in the 1923 Oldsmobile Model 30 luxury car until it was replaced in 1950 by Oldsmobile's V8 engine.
The 1913–1929
Oakland Six
The Oakland Six was the first six-cylinder engine offered by the Oakland Motor Company in 1913 which became a division of General Motors in 1909. The Oakland Six was offered in many different model names that changed every year, along with severa ...
luxury car was powered by a flathead petrol engine produced in displacements of and . In 1926, the
Pontiac Six
The Pontiac 6 was a more affordable version of its predecessor Oakland Six that was introduced in 1926, sold through Oakland Dealerships. Pontiac was the first of General Motors companion make program where brands were introduced to fill in pricin ...
was introduced as a lower-cost version of the Oakland six, powered by the Pontiac Split-Head Six flathead engine, which used two cylinder heads. This engine was replaced by the 1941–1954 Pontiac flathead six. The unrelated Pontiac OHV 6 overhead valve engine was produced in 1964–1965, based on a Chevrolet design. Pontiac's final straight-six engine was the 1966–1969 Pontiac OHC 6 overhead camshaft engine, which was replaced by Chevrolet's straight-six engine and Buick's V6 engine.
a
The overhead valve Buick Straight-6 petrol engine was introduced in the 1914
Buick Six
The Buick Six was a top level automobile produced by GM's Buick Division which was first introduced in 1914, and was the senior vehicle to the Buick Series B Four. It was an all new platform which was shared with the Oldsmobile Six and was the ...
luxury car and was produced until 1930. Buick did not make another six-cylinder engine until they introduced a V6 engine in 1962.
The 1916 through 1926 Hudson Super Six was powered by a straight-six petrol engine. This was followed by an IOE version in 1916. The 1951
Hudson Hornet
''For the NASCAR car, see Fabulous Hudson Hornet.''
The Hudson Hornet is a full-size car manufactured by Hudson Motor Car Company of Detroit, Michigan from 1951 until 1954, when Nash-Kelvinator and Hudson merged to form American Motors Corpor ...
introduced a flathead straight-six engine. These engines dominated dirt track and NASCAR racing at the time. Production of the Hudson I6 continued after the 1954 merger forming
American Motors Corporation
American Motors Corporation (AMC; commonly referred to as American Motors) was an American automobile manufacturing company formed by the mergers and acquisitions, merger of Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1, 19 ...
and was eventually replaced by a new
Rambler V8
The Rambler Six and the Rambler V8 are Mid-size car, intermediate sized automobiles that were built and marketed by American Motors Corporation (AMC) for model years 1956 through 1960.
Launched on 15 December 1955, the 1956 model year Rambler ...
after 1956.
In 1924, Chrysler began production of a straight six version of the Chrysler flathead petrol engine. This was replaced by the 1959–2000 Chrysler Slant-6 overhead valve straight-six petrol engine, which was so named due to the 30-degree angle used to reduce the height of the engine (with the trade-off of a wider engine). The Slant-6 was released in the
Dodge Dart
The Dodge Dart is a line of passenger cars produced by Dodge from the 1959 to 1976 model years in North America, with production extended to later years in various other markets.
The production Dodge Dart was introduced as a lower-priced full-si ...
economy car and used in many models until a V6 engine replaced it after 30 years.
The Chevrolet Stovebolt overhead valve straight-six petrol engine was introduced in 1929 as a replacement for the brand's straight-four engines and was produced in displacements of , and . The second generation of this engine family - often referred to as the Blue Flame engine - was produced from 1937 to 1962 in displacements of , and . This was followed by the 1962–1988
Chevrolet Turbo-Thrift engine
The Chevrolet Turbo-Thrift engine is a Straight-six engine, straight-six produced from 1962 to 2001 by the Chevrolet division of General Motors. The entire series of engines was commonly called ''Turbo-Thrift'', although the name was first used on ...
(also using an overhead valve design), which was replaced by various General Motors V6 engines.
The 1952 through 2006 AMC Straight-6 petrol engine initially used a flathead design before being upgraded to an overhead valve design in 1956. A new I6 design with a short stroke and seven
main bearing
A main bearing is a bearing in a piston engine which holds the crankshaft in place and allows it to rotate within the engine block.
The number of main bearings per engine varies between engines, often in accordance with the forces produced b ...
crankshaft was introduced in 1964. The engine was rugged, reliable, and became noted for longevity. A turbocharged racing engine based on the AMC Straight-6 engine block produced and competed in the 1978 Indianapolis 500 race. The final application for the AMC Straight-6 engine was the 2006
Jeep Wrangler (TJ)
The Jeep Wrangler (TJ) is the second generation of the Jeep Wrangler off-road and sport utility vehicle (SUV). Introduced in 1996 as a 1997 model, the TJ reintroduced the circular headlights the classic Jeep models had been known for. For the 2004 ...
, after which a V6 replaced it.
The 1962 through 1973 Jeep Tornado overhead camshaft straight-six engine was introduced in the
Willys Jeep Station Wagon
The Willys Jeep Station Wagon, Jeep Utility Wagon and Jeep Panel Delivery are automobiles produced by Willys and Kaiser Jeep in the United States from 1946 to 1964, with production in Argentina and Brazil continuing until 1970 and 1977, respecti ...
. At the time of its introduction, the Tornado engine had the lowest specific fuel consumption of an American gasoline (petrol) engine. The Tornado engine was replaced by the AMC I6 engine.
In 2001, General Motors resumed production of straight-six engines with the Vortec 4200 dual overhead camshaft petrol engine. This engine was used in various SUV models until 2009. Also, the Duramax Straight-6 turbocharged diesel engine has been available in several General Motors SUV and light truck models since 2020.
On March 25, 2022, Stellantis announced their new turbocharged straight-six engine, called Hurricane. Two outputs are available, a standard high performance rated at of torque. The turbos on the Hurricane Standard Output deliver a peak boost of 22 psi, while the Hurricane High Output turbos deliver 26 psi of peak boost. The 3.0 L Hurricane is produced at Stellantis’ Saltillo Engine Plant in Mexico.
Asia
Toyota's first straight-six engine was the Toyota Type A, produced from 1935 through 1947. The Type A was an overhead-valve petrol engine based on the ''Chevrolet Stovebolt'' engine. This was followed by the first generation Toyota F overhead valve engine, which was produced from 1949 to 1975, which in turn was followed by the 2F version from 1975 to 1988 and the fuel-injected 3F / 3FE version from 1988 to 1992. This was replaced by the dual overhead camshaft
Toyota FZ engine
The Toyota FZ engine was a 24-valve, DOHC straight-6 internal combustion engine manufactured by Toyota to replace the F-series engine. It was used primarily in SUVs because of its large displacement, smoothness, ruggedness and torque.
Technical ...
, produced from 1993 until 2008. Produced alongside these engines was the single overhead camshaft
Toyota M engine
Toyota Motor Corporation's M family of engines were a Longitudinal engine, longitudinally mounted straight-6 engine design. They were used from the 1960s through the 1990s. All M family engines were OHC designs. While the M family was born with ...
, which was introduced in 1965 and produced over seven generations until 1993 (with the ''7M-GTE'' being the final version of the M engine). The M engine was replaced by the dual overhead camshaft
Toyota JZ engine
The Toyota JZ engine family is a series of inline-6 automobile engines produced by Toyota. As a replacement for the M-series inline-6 engines, the JZ engines were 24-valve DOHC engines in 2.5- and 3.0-litre versions.
1JZ
The 1JZ version w ...
, which was produced from 1990 to 2007 and is arguably known as Toyota's best straight-six engine. Toyota's third line of straight-six engines was the 2.0 L
Toyota G engine
The Toyota Motor Corporation
is a Japanese Multinational corporation, multinational Automotive industry, automotive manufacturer headquartered in Toyota City, Aichi, Japan. It was founded by Kiichiro Toyoda and incorporated on August 28, 1 ...
, which was released as a single overhead camshaft engine in 1979 and upgraded to dual overhead camshafts before production ended in 2008 (with the 1G-FE being the final variant).
Nissan's first straight-six engine was the 1950–1952 Nissan NAK flathead petrol engine, which continued in various forms until production of the Nissan P engine ended in 2003. The 1963-1965 Nissan K overhead valve petrol engine was used in the Nissan Cedric Special 50 luxury car. Using a similar design, the Nissan H30 engine was used in several luxury cars from 1965 through 1989. In 1966, Nissan began production of the six-cylinder versions of the Nissan L single overhead camshaft engine, which was produced until 2009. The 1985–2004
Nissan RB engine
The RB engine is an oversquare 2.0–3.0 L straight-6 Four-stroke cycle, four-stroke Petrol engine, gasoline engine from Nissan, originally produced from 1985 to 2004. The RB followed the 1983 Nissan VG engine, VG-series V6 engines to offe ...
, used in the
Nissan Skyline
The is a brand of automobile originally produced by the Prince Motor Company starting in 1957, and then by Nissan after the two companies merged in 1967. After the merger, the Skyline and its larger counterpart, the Nissan Gloria, were sold in ...
and several other cars, was produced in single overhead camshaft and dual overhead camshaft configurations until a V6 engine replaced it. The Nissan TB overhead valve engine was introduced in 1987 and produced alongside the other straight-six engines.
The six-cylinder versions of the
Prince G engine
The Prince Motor Company, Prince G-series engine was the company's only Inline-four engine, straight-four and straight-six engines which began production in 1955. A number of variations were made, with both Overhead valve, OHV and OHC heads. A di ...
were introduced in 1963 and remained in production until 1969, three years after Prince's merger with Nissan. The 1969–1973 Nissan S20 dual overhead camshaft engine (used in the
Nissan Fairlady
The Datsun Sports (called Datsun Fairlady in the Japanese and Australian markets and simply given a numerical designation alone in other export markets), was a series of roadsters produced by Nissan in the 1960s. The series was a predecessor to th ...
and first generation of the
Nissan Skyline GT-R
The is a Japanese sports car based on the Nissan Skyline range. The first cars named "Skyline GT-R" were produced between 1969 and 1972 under the model code KPGC10, and were successful in Japanese touring car racing events. This model was fol ...
) was based on the Prince G engine.
Mitsubishi produced six-cylinder versions of the
Mitsubishi KE engine
The Mitsubishi KE engine is a range of engines produced by Mitsubishi Motors during the 1960s and early 1970s. They were extensively used in the various Colt-branded vehicles the company produced from 1963.
The engines were overhead valve iron-b ...
from 1963 to 1970, as well as the rare six-cylinder versions of the Mitsubishi 6G34 version of the single overhead camshaft "Saturn" engine from 1970 to 1976.
The 2000–2006
Daewoo Magnus
The Daewoo Magnus is a mid-sized sedan developed and manufactured by Daewoo for model years 2000–2006 under a single generation, and marketed globally by GM Daewoo and other General Motors divisions, as well as GMDAT stake holder Suzuki. Deve ...
(also called the Chevrolet Evanda, Chevrolet Epica, Holden Epica, or Suzuki Verona) was powered by the ''Daewoo XK6'' straight-six petrol engine, which is one of the few straight-six engines to be used in a
transverse engine
A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the direction of travel. Many modern front-wheel drive vehicles use this arrangement. Most rear-wheel drive vehicles use a longitudinal ...
front-wheel drive car.
Australia
From the 1950s to the 2010s, many cars produced in Australia were powered by a straight-six engine.
Holden's first car, the 1948
Holden 48-215
The Holden 48-215 is a mid-size car, mid-size sedan (automobile), sedan which was produced by the Australian automaker Holden between November 1948 and October 1953. A coupe utility derivative, coded as the 50-2106 and marketed as the Holden Cou ...
sedan, was powered by the Holden 'grey' motor, an overhead valve petrol engine. This engine was replaced by the Holden 'red' motor, which was produced from 1963 to 1980 and in turn followed by the 1980–1984 Holden 'blue' motor. The final locally produced Holden straight-six was the 1984–1986 Holden 'black' motor, which was initially replaced by the Japanese-built Nissan RB30 engine before Holden switched to a locally-built V6 engine.
Ford produced straight-six engines for the longest time of any Australian manufacturer. In 1960, the
Ford Falcon
The Ford Falcon is an automobile nameplate by Ford Motor Company, Ford that applied to several vehicles worldwide.
* Ford Falcon (North America), an automobile produced by Ford from 1960 to 1970.
* Ford Falcon (Argentina), a car built by Ford ...
large sedan was introduced with a locally-built version of the American Ford Straight-6 overhead valve engine. In 1998, these engines were upgraded to a single overhead camshaft design. This was followed in 2002 by the Ford Barra dual overhead camshaft engine in 2002, which was produced in both naturally aspirated and turbocharged versions. The Ford Barra engine remained in use until Ford Australia ceased local production in 2016.
The
Chrysler Valiant
The Chrysler Valiant was a full-size car which was sold by Chrysler Australia between 1962 and 1981. Initially a rebadged locally assembled Plymouth Valiant from the United States, from the second generation launched in 1963, the Valiant was fu ...
was introduced in 1962, powered by the American Chrysler Slant 6. In 1970, the Valiant switched to the Chrysler Hemi-6 overhead valve engine, an Australia-only engine that was produced until Chrysler Australia ceased production of large cars in 1981.
The 1962–1965
Austin Freeway
The Austin Freeway is an automobile which was developed by BMC Australia, based on the British Austin A60 Cambridge. Introduced in 1962, it was marketed under the Austin name in both four-door sedan and five-door station wagon body styles.
U ...
and
Wolseley 24/80
The Wolseley 24/80 is an automobile produced by British Motor Corporation (Australia) from May 1962 to October 1965,BMC E-series overhead camshaft engines, which were introduced in the 1970 Austin Kimberley / Austin Tasman front-wheel-drive sedans, which were produced until 1972. This engine was upsized to a 2.6 L displacement in 1973 and used
Leyland P76
The Leyland P76 is a large car that was produced by Leyland Australia, the Australian subsidiary of British Leyland. Featuring what was described at the time as the "standard Australian wheelbase of 111 inches", it was intended to provide the c ...
and the
Morris Marina
The Morris Marina is a front-engined, rear-wheel-drive C-segment, small family car that was manufactured by the Morris Motors, Austin-Morris division of British Leyland from 1971 until 1980. It served to replace the Morris Minor in the Mo ...
large cars until 1975.
Usage in motorcycles
From 1964 to 1967, Honda produced several
Grand Prix motorcycle racing
Grand Prix motorcycle racing is the highest class of motorcycle road racing events held on Road racing, road circuits sanctioned by the Fédération Internationale de Motocyclisme (FIM). Independent motorcycle racing events have been held sin ...
motorcycles powered by straight-six versions of the Honda RC petrol racing engine; these versions were designated the '3RC164', 'RC165', 'RC166' and
Honda RC174
The Honda RC174 was a road racing, racing motorcycle built by Honda for the 350 cc class of Grand Prix motorcycle racing in the 1967 season. Based on the 250 cc class Honda RC166, it had less than 300 cc, yet won seven out of the ...
. The unrelated road-use
Honda CBX
The Honda CBX Types of motorcycles#Sport bike, sports motorcycle was manufactured by Honda from 1978 to 1982. With a 1047cc Straight-six engine, transverse six-cylinder engine producing , it was the flagship of the Honda range. The CBX was well r ...
was produced from 1978 to 1982 and was powered by a dual overhead camshaft petrol engine.
The 1973–1989 Benelli Sei series was the first road-use motorcycle to use a straight-six engine. Initially released with a single overhead camshaft petrol engine, in 1979 it was upgraded to a engine.
The 1979–1989 Kawasaki Z1300 roadster motorcycle was powered by a dual overhead camshaft petrol engine.
From 2011–present, the
BMW K1600
The BMW K1600GT, K1600GTL, K1600 Grand America and K1600B are Touring motorcycles manufactured by BMW Motorrad. The former two were announced in July 2010,
unveiled at the Intermot motorcycle show in Cologne in October 2010; they went on sale in ...
series of touring motorcycles have been powered by a dual overhead camshaft petrol engine.
Usage in trucks
Straight-six engines used in trucks include:
* 5.9 and 6.7 L versions of the 1984–present Cummins B Series turbocharged diesel engine
* General Motors' 2002–2009 Vortec 4200 naturally-aspirated petrol engine
Diesel engines
Automotive engines
Straight-six engines used in automobiles include:
* 1978-1995 Volkswagen D24 naturally-aspirated engine and the 1982–1992 Volkswagen D24T turbocharged engine
* 1986-1997
Mercedes-Benz OM603
The OM603 engine was a straight-6 Diesel automobile engine from Mercedes-Benz used from 1984 through 1999. The 603 saw limited use in the W124
The Mercedes-Benz W124 is a range of executive cars made by Daimler-Benz from 1984 to 1997. The ran ...
engine - produced in naturally aspirated and turbocharged variants
* BMW's line of diesel engines consists of the
BMW M21
The BMW M21 is a straight-six diesel engine developed by the German engine manufacturer BMW. It has swirl chamber injection and is based on the BMW M20, M20 petrol engine and was produced for BMW by the Oberösterreich, Upper Austrian Steyr-Daimle ...
(introduced in 1981) through to the current
BMW B57
The BMW B57 is a turbo-diesel straight-six engine, produced by BMW since 2015.
Design
The B57 belongs to a family of modular engines, including the B37 and B47 diesel engines, and B38, B48, and B58 petrol engines. The engines utilise a co ...
engine
* 1985-2009 Nissan RD (naturally-aspirated and turbocharged variants) and 1987-2007 Nissan TD42 (turbocharged) engines
*
General Motors
General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. The company is most known for owning and manufacturing f ...
Toyota engines
This is a list of piston engines developed, independently or with other car companies, by Toyota Motor Corporation.
Engine codes
Toyota has produced a wide variety of automobile engines, including three-cylinder, four-cylinder, V6 and V8 engin ...
from 1956–present
*
Caterpillar
Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).
As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...
manufactures several inline six-cylinder diesel engines, known for their reliability and use in various industrial and commercial applications. These engines include the C13, C7, 3126, and others, ranging in size and power output.
* Cummins B Series (5.9 and 6.7 L versions) from 1984–present
* industrial and truck engines from
International
International is an adjective (also used as a noun) meaning "between nations".
International may also refer to:
Music Albums
* ''International'' (Kevin Michael album), 2011
* ''International'' (New Order album), 2002
* ''International'' (The T ...
,
MAN Truck & Bus
MAN Truck & Bus SE (formerly MAN Nutzfahrzeuge AG, ) is a German automotive manufacturer and the subsidiary of Traton, one of the leading international providers of commercial vehicles. Headquartered in Munich, Germany, MAN Truck & Bus produces v ...
,
Scania
Scania ( ), also known by its native name of Skåne (), is the southernmost of the historical provinces of Sweden, provinces () of Sweden. Located in the south tip of the geographical region of Götaland, the province is roughly conterminous w ...
V12 engine
A V12 engine is a twelve-Cylinder (engine), cylinder Internal combustion engine#Reciprocating engines, piston engine where two banks of six cylinders are arranged in a V engine, V configuration around a common crankshaft. V12 engines are more c ...
is a twelve-
cylinder
A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.
A cylinder may also be defined as an infinite ...
piston engine
A reciprocating engine, more often known as a piston engine, is a heat engine that uses one or more Reciprocating motion, reciprocating pistons to convert high temperature and high pressure into a Circular motion, rotating motion. This article ...
where two six cylinder banks are arranged in a V configuration around a common
crankshaft
A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...
.
See also
*
Flat-six engine
A flat-six engine, also known as a horizontally opposed-six, is a six-cylinder piston engine with three cylinders on each side of a central crankshaft. The most common type of flat-six engine is the boxer-six engine, where each pair of opposed c ...
*
V6 engine
A V6 engine is a six- cylinder piston engine where the cylinders and cylinder blocks share a common crankshaft and are arranged in a V configuration.
The first V6 engines were designed and produced independently by Marmon Motor Car Company, ...
*
VR6 engine
The VR6 engine is a six-cylinder engine configuration developed by Volkswagen. The name VR6 comes from the combination of German words "Verkürzt" and "Reihenmotor" meaning "shortened inline engine" referring to the VR-engine having characteristi ...
*
V12 engine
A V12 engine is a twelve-Cylinder (engine), cylinder Internal combustion engine#Reciprocating engines, piston engine where two banks of six cylinders are arranged in a V engine, V configuration around a common crankshaft. V12 engines are more c ...