Straight-4
Overview
 
The inline-four engine or straight-four engine is an internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 with all four cylinders
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...

 mounted in a straight line, or plane along the crankcase
Crankcase
In an internal combustion engine of the reciprocating type, the crankcase is the housing for the crankshaft. The enclosure forms the largest cavity in the engine and is located below the cylinder, which in a multicylinder engine are usually integrated into one or several cylinder blocks...

. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...

s driving a common crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

. Where it is inclined, it is sometimes called a slant-four. In a specification chart or when an abbreviation is used, an inline-four engine is listed either as I4 or L4 (for longitudinal, to avoid confusion between the digit 1 and the letter I).

The inline-four layout is in perfect primary balance
Engine balance
Engine balance is the design, construction and tuning of an engine to run smoothly. Improving engine balance reduces vibration and other stresses and can improve the overall performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress on other machinery...

 and confers a degree of mechanical simplicity which makes it popular for economy cars.
Encyclopedia
The inline-four engine or straight-four engine is an internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 with all four cylinders
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...

 mounted in a straight line, or plane along the crankcase
Crankcase
In an internal combustion engine of the reciprocating type, the crankcase is the housing for the crankshaft. The enclosure forms the largest cavity in the engine and is located below the cylinder, which in a multicylinder engine are usually integrated into one or several cylinder blocks...

. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...

s driving a common crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

. Where it is inclined, it is sometimes called a slant-four. In a specification chart or when an abbreviation is used, an inline-four engine is listed either as I4 or L4 (for longitudinal, to avoid confusion between the digit 1 and the letter I).

The inline-four layout is in perfect primary balance
Engine balance
Engine balance is the design, construction and tuning of an engine to run smoothly. Improving engine balance reduces vibration and other stresses and can improve the overall performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress on other machinery...

 and confers a degree of mechanical simplicity which makes it popular for economy cars. However, despite its simplicity, it suffers from a secondary imbalance which causes minor vibrations in smaller engines. These vibrations become worse as engine size and power increase, so the more powerful engines used in larger cars generally are more complex designs with more than four cylinders.

Today almost all manufacturers of four-cylinder engines for automobiles produce the inline-four layout, with Subaru
Subaru
; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...

's Flat-four engine being a notable exception, and so four-cylinder is synonymous with and a more widely used term than inline-four. The inline-four is the most common engine configuration in modern cars, while the V6 engine
V6 engine
A V6 engine is a V engine with six cylinders mounted on the crankcase in two banks of three cylinders, usually set at either a right angle or an acute angle to each other, with all six pistons driving a common crankshaft...

 is the second most popular. In the late 2000s, with auto manufacturers making efforts to reduce emissions; and increase fuel efficiency due to the high price of oil and the economic recession, the proportion of new vehicles with four-cylinder engines (largely of the inline-four type) rose from 30 percent to 47 percent between 2005 and 2008, particularly in mid-size vehicles where a decreasing number of buyers have chosen the V6 performance option.

Displacement

This inline engine
Straight engine
Usually found in four- and six-cylinder configurations, the straight engine, or inline engine is an internal-combustion engine with all cylinders aligned in one row, with no offset...

 configuration is the most common in car
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

s with a displacement
Engine displacement
Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...

 up to 2.4 L. The usual "practical" limit of the displacement of inline-four engines in a car is around 2.7 L. However, Porsche
Porsche
Porsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....

 used a 3.0 L four in its 944 S2
Porsche 944
The Porsche 944 is a sports car built by Porsche from 1982 to 1991. It was built on the same platform as the 924, although 924 production continued through 1988. The 944 was intended to last into the 1990s, but major revisions planned for a 944 S3 model were eventually rolled into the 968 instead,...

 and 968
Porsche 968
The 968 is a sports car sold by Porsche AG from 1992 to 1995. It took over the entry-level position in Porsche's lineup from the 944, with which it shared about 20% of its parts...

 sports cars; and Rolls Royce
Rolls-Royce Motors
Rolls-Royce Motors was created from the de-merger of the Rolls-Royce car business from Rolls-Royce Limited in 1973. The original Rolls-Royce Limited had been nationalised in 1971 due to the financial collapse of the company, caused in part by the development of the RB211 jet engine...

 produced several inline-four engines of 2,838 cc with basic cylinder dimensions of 3.5 in (88.9 mm) diameter and 4.5 in (114.3 mm) stroke (Rolls Royce B40). Early vehicles also tended to have engines with larger displacements to develop horsepower and torque. The Model A Ford was built with a 3.3 L inline-four engine.

Inline-four diesel engines, which are lower revving than gasoline engines, often exceed 3.0 L. Mitsubishi
Mitsubishi
The Mitsubishi Group , Mitsubishi Group of Companies, or Mitsubishi Companies is a Japanese multinational conglomerate company that consists of a range of autonomous businesses which share the Mitsubishi brand, trademark and legacy...

 still employs a 3.2 L inline-four turbodiesel
Turbodiesel
Turbodiesel refers to any diesel engine with a turbocharger. Turbocharging is the norm rather than the exception in modern car and truck diesel engines...

 in its Pajero (called the Shogun or Montero in certain markets), and Tata Motors
Tata Motors
Tata Motors Limited is an Indian multinational automotive corporation headquartered in Mumbai, India. Part of the Tata Group, it was formerly known as TELCO...

 employs a 3.0 L inline-four diesel in its Spacio
Tata Sumo
Tata Sumo is a multi-utility vehicle produced by India's largest automotive companyTata Motors. The vehicle was launched in 1994 and was one of the first passenger vehicles designed in India. The Sumo received an extensive facelift in 2004 and was renamed the Sumo Victa in face of competition from...

 and Sumo Victa
Tata Sumo
Tata Sumo is a multi-utility vehicle produced by India's largest automotive companyTata Motors. The vehicle was launched in 1994 and was one of the first passenger vehicles designed in India. The Sumo received an extensive facelift in 2004 and was renamed the Sumo Victa in face of competition from...

.

The Toyota B engine series
Toyota B engine
The Toyota B engine family was a series of inline-4 diesel engines.Toyota also had a 3.4 L inline-6 gasoline engine from 1937 to 1947 that was also called the B engine. The earlier engine was used in early Toyota cars and trucks and in the first version of the Land Cruiser when it was known...

 of diesel engines varies in displacement from 3.0- 4.1 L. The largest engine in that series was used in the Mega Cruiser
Toyota Mega Cruiser
The Toyota Mega Cruiser is a large, heavy-duty sport utility vehicle introduced by Toyota in 1995. The largest SUV ever built by Toyota, it resembled the Hummer H1, and like the Hummer, was designed primarily for military use with the Mega Cruiser seeing duty as infantry transports equipped with...

.

One of the strongest Powerboat-4-cylinders is the Volvo Penta
Volvo Penta
Volvo Penta was founded in 1907 in conjunction with the production of the first marine engine, B1. The Penta company soon became an established internal combustion engine manufacturer, which in 1927 delivered the engine to Volvo's first passenger car....

 D4-300 turbodiesel. This is a 3.7 L-inline-4 with 300 hp and 516 lbft .

One of the strongest inline-4-engines is the MAN D0834 engine. This is a 4.6 L inline-4 with 220 hp and 627 lbft, which is available for the MAN TGL light-duty truck and VARIOmobil motorhomes.

The Isuzu Forward
Isuzu Forward
The Isuzu Forward & Isuzu F-Series is a line of medium-duty commercial vehicles built by Isuzu. All F-series trucks are cab over designs and the cabin comes fully built from the factory. Most models come with a diesel engine; but, some markets get CNG derivatives as well...

 is a medium-duty truck which is available with a 5.2 L inline-four engine that delivers 210 hp and 470 lbft .

The Hino Ranger
Hino Ranger
The Hino Ranger is a medium to heavy duty cab-over truck manufactured by Hino Motors.The Ranger is part of Hino's F-Series Truck with model code such as FC, FD, FE, FF, FG, FL, and FM. The further the alphabet means the higher payload. The 4WD models are FT and GT. The SG is Tractor Head to pull...

 is a medium-duty truck which is available with a 5.1 L inline-four engine that delivers 175 hp and 465 lbft .
The earlier Hino Ranger
Hino Ranger
The Hino Ranger is a medium to heavy duty cab-over truck manufactured by Hino Motors.The Ranger is part of Hino's F-Series Truck with model code such as FC, FD, FE, FF, FG, FL, and FM. The further the alphabet means the higher payload. The 4WD models are FT and GT. The SG is Tractor Head to pull...

 even had a 5.3 L inline-four engine.

The Kubota
Kubota
, is a tractor and heavy equipment manufacturer based in Osaka, Japan. One of its notable contributions was to the construction of the Solar Ark. The company was established in 1890.The company produces many products including:...

 M135X is a tractor with a 6.1 L inline-four. This turbo-diesel engine has a bore of 118 mm (4.6 in) and a relative long stroke of 140 mm (5.5 in).

Larger inline-four engines are used in industrial applications, such as in small trucks and tractors, are often found with displacements up to about 4.6 L. Diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s for stationary, marine and locomotive
Diesel locomotive
A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

 use (which run at low speeds) are made in much larger sizes.

Brunswick Marine
Mercury Marine
Mercury Marine, founded in 1939, is a division of Brunswick of Lake Forest, Illinois, in the United States. Mercury provides engines for private, commercial and government sales. Mercury also has its own line of very successful racing engines tailored for power and speed. The company's primary...

 built a 170 bhp 3.7 L 4-cylinder gasoline engine (designated as the "470") for their Mercruiser Inboard/outboard line. The block was formed from one half of a Ford 460 cubic inch V8 engine. This engine was produced in the 1970s and 1980s.

One of the largest inline-four engines is the MAN B&W 4K90 marine engine. This two-stroke turbo-diesel has a giant displacement of 6,489 L. This results from a massive 0.9 meter bore and 2.5 meter stroke. The 4k90 engine develops 18280 kW at 94 rpm and weighs 787 tons.

Displacement can also be very small, as found in kei cars sold in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, such as the Subaru EN series
Subaru EN engine
The EN series engine is used for kei cars sold by Subaru in Japan. It is a four-cylinder, four-cycle engine introduced in 1988 as a replacement for the EK23 that was used in the Subaru Rex. While others manufacturers adopted a three-cylinder engine, the Subaru-EN is a four-cylinder. The EN05...

; engines that started out at 550 cc and are currently at 660 cc, with variable valve timing
Variable valve timing
In internal combustion engines, variable valve timing , also known as Variable valve actuation , is a generalized term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine...

, DOHC and superchargers resulting in engines that produce 65 PS.

Balance and smoothness

The inline-four engine is much smoother than one-, two-, and three-cylinder engines, and this has resulted in it becoming the engine of choice for most economy cars, although it can be found in some sports cars as well. However, the inline-four is not a fully balanced
Engine balance
Engine balance is the design, construction and tuning of an engine to run smoothly. Improving engine balance reduces vibration and other stresses and can improve the overall performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress on other machinery...

 configuration.

An even-firing inline-four engine is in primary balance because the pistons are moving in pairs, and one pair of pistons is always moving up at the same time as the other pair is moving down. However, piston acceleration and deceleration are greater in the top half of the crankshaft rotation than in the bottom half, because the connecting rods are not infinitely long, resulting in a non sinusoidal motion. As a result, two pistons are always accelerating faster in one direction, while the other two are accelerating more slowly in the other direction, which leads to a secondary dynamic imbalance that causes an up-and-down vibration at twice crankshaft speed. This imbalance is tolerable in a small, low-displacement, low-power configuration, but the vibrations get worse with increasing size and power.

The reason for the piston's higher speed during the 180° rotation from mid-stroke through top-dead-centre, and back to mid-stroke, is that the minor contribution to the piston's up/down movement from the connecting rod's change of angle here has the same direction as the major contribution to the piston's up/down movement from the up/down movement of the crank pin. By contrast, during the 180° rotation from mid-stroke through bottom-dead-centre and back to mid-stroke, the minor contribution to the piston's up/down movement from the connecting rod's change of angle has the opposite direction of the major contribution to the piston's up/down movement from the up/down movement of the crank pin.

Most inline-four engines below 2.0 L in displacement rely on the damping effect of their engine mounts to reduce the vibrations to acceptable levels. Above 2.0 L, most modern inline-four engines now use balance shaft
Balance shaft
In piston engine engineering, a balance shaft is an eccentric weighted shaft which offsets vibrations in engine designs that are not inherently balanced...

s to eliminate the second-order harmonic vibrations. In a system invented by Dr. Frederick W. Lanchester in 1911, and popularised by Mitsubishi Motors
Mitsubishi Motors
is a multinational automaker headquartered in Minato, Tokyo. In 2009 it was the fifth-largest Japan-based automaker and the 17th-largest in the world measured by production...

 in the 1970s, an inline-four engine uses two balance shafts, rotating in opposite directions at twice the crankshaft's speed, to offset the differences in piston speed. However, in the past, there were numerous examples of larger inline-fours without balance shafts, such as the Citroën DS 23
Citroën DS
The Citroën DS is an executive car produced by the French manufacturer Citroën between 1955 and 1975. Styled by Italian sculptor and industrial designer Flaminio Bertoni and the French aeronautical engineer André Lefèbvre, the DS was known for its aerodynamic futuristic body design and innovative...

 2,347 cc engine that was a derivative of the Traction Avant
Citroën Traction Avant
The Citroën Traction Avant is an automobile which was produced by the French manufacturer Citroën from 1934 to 1957. About 760,000 units were produced.-Impact on the world:...

 engine, the 1948 Austin
Austin Motor Company
The Austin Motor Company was a British manufacturer of automobiles. The company was founded in 1905 and merged in 1952 into the British Motor Corporation Ltd. The marque Austin was used until 1987...

 2,660 cc engine used in the Austin-Healey 100
Austin-Healey 100
The Austin-Healey 100 is a sports car built from 1953 until 1959. There were two models, the original four-cylinder Austin-Healey 100, built 1953-1956, and the six-cylinder Austin-Healey 100-6, built 1956-1959....

 and Austin Atlantic
Austin Atlantic
The Austin A90 Atlantic was a British car produced by the Austin Motor Company, launched initially as a sporting four seat convertible. It made its début at the 1948 Earls Court Motor Show in London, with production models built between spring 1949 and late 1950...

, the 3.3 L flathead engine
Flathead engine
A flathead engine is an internal combustion engine with valves placed in the engine block beside the piston, instead of in the cylinder head, as in an overhead valve engine...

 used in the Ford Model A (1927)
Ford Model A (1927)
The Ford Model A of 1927–1931 was the second huge success for the Ford Motor Company, after its predecessor, the Model T. First produced on October 20, 1927, but not sold until December 2, it replaced the venerable Model T, which had been produced for 18 years...

, and the 2.5 L GM Iron Duke engine
GM Iron Duke engine
Iron Dukes were fitted with fuel injection in 1982. This version was christened the Tech IV, though Car and Driver later ridiculed it as the low-Tech IV. Power output remained at ....

 used in a number of American cars and trucks. Soviet/Russian GAZ Volga
Volga (automobile)
Volga is an automobile brand that originated in the Soviet Union to replace the venerated GAZ-M20 Pobeda in 1956. Modern in design, it became a symbol of higher status in the Soviet nomenklatura...

 cars and UAZ
UAZ
UAZ , Ulyanovsky Avtomobilny Zavod is an automobile manufacturer based in Ulyanovsk, Russia which manufactures off-road vehicles, buses and trucks. It is best known for its Model 469 jeep, which has seen wide use as a military vehicle in Russia and around the world...

 SUVs, vans and light trucks used aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 big-bore inline-four engines (2.5 or later 2.9 L) with no balance shafts from the 1950s-1990s. These engines were generally the result of a long incremental evolution process and their power was kept low compared to their capacity. However, the forces increase with the square of the engine speed — that is, doubling the speed makes the vibration four times worse — so modern high-speed inline-fours have more need to use balance shafts to offset the vibrations.

Four-cylinder engines also have a smoothness problem in that the power strokes of the pistons do not overlap. With four cylinders and four strokes to complete in the four-stroke cycle, each piston must complete its power stroke and come to a complete stop before the next piston can start a new power stroke, resulting in a pause between each power stroke and a pulsating delivery of power. In engines with more cylinders, the power strokes overlap, which gives them a smoother delivery of power and less vibration than a four can achieve. As a result, six- and eight- cylinder engines are generally used in more luxurious and expensive cars.

Notable production inline-four engines

The smallest automobile production inline-four engine powered the 1962-1970 Mazda P360 Carol
Mazda Carol
The Mazda Carol is a name used by Mazda for its kei cars from 1962 until 1970. It was revived again with Mazda's 1989 reentry into the Kei car class.-Carol :...

 kei car
Kei car
Kei cars, K-cars, or , are a Japanese category of small vehicles, including passenger cars, vans, and pickup trucks. They are designed to comply with Japanese government tax and insurance regulations, and in most rural areas are exempted from the requirement to certify that adequate parking is...

. Displacing just 358 cc, the Mazda DA was a conventional but tiny pushrod engine. Honda produced, from 1963 to 1967, a 356 cc inline-four engine for the T360
Honda T360
The T360 was a pickup truck from Honda. Introduced in June 1963, it was Honda's first production automobile.The T360 used a 356 cc AK250E series DOHC straight-4 engine also found in the Honda S360 roadster prototype. The mid-mounted unit propelled the truck to a top speed of . The engine...

 truck. Inline-four motorcycle engines are built down to 250 cc, e.g. in the Honda CBR250
Honda CBR250
The CBR250 series of motorcycles was produced by Honda between 1986 and 1996. It is a lightweight sport bike with a six-speed gearbox and a , four-cylinder, four-stroke engine capable of revving up to 19,000 rpm...

.

Most inline-four engines, however, have been over 700 cc displacement. A practical upper limit could be placed in the 2.5 L range for contemporary production cars. Larger engines (up to 6.1 L) have been seen in tractors (Kubota M135X) and medium duty truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

 use (Isuzu Forward, Hino Ranger), especially using diesel fuel (one of the strongest is the MAN D0834 engine with 220 hp and 627 lbft ). The use of balance shafts allowed Porsche
Porsche
Porsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....

 to use a 3.0 L (2990 cc) inline-four engine on road cars first in the 944 S2, but the largest modern non-diesel was the plain 3188 cc 195 in the 1961 Pontiac Tempest
Pontiac Tempest
The Pontiac Tempest was an entry-level compact produced by the Pontiac Motor Division of General Motors, introduced in September 1960 for the 1961 model year....

.

Currently, one of the largest straight-4 engines in production is General Motors' Vortec 2900 installed in the GMC Canyon and Chevrolet Colorado small pickup trucks. It shares the same 95.5 mm (3.8 in) bore and 102 mm (4.0 in) stroke as the larger inline-five Vortec 3700. The latest version of the Vortec 2900, the LLV, displaces 2.9 L (2921 cc, 178 in³) and produces 185 hp at 5600 rpm and 195 lbft at 2800 rpm. Engine redline is 6300 rpm. Another example of a large inline-four engine is the Russian 2.89 L UMZ 421 series UMZ engine.

In the early 20th century, bigger engines existed, both in road cars and sports cars. Due to the absence of displacement limit regulations, manufacturers took increasing liberties with engine size. In order to achieve power over 100 hp, most engine builders simply increased displacement, which could sometimes achieve over 10.0 L. One of the biggest inline-fours of its time was De Dietrich
De Dietrich
De Dietrich is a holding company based in France which traces its history back to the early 17th century. It was active in the automobile, railway and industrial machines industry. It sold it holding stake in De Dietrich Ferroviaire to Alstom in 1990...

 17,000 cc engine. Its cubic capacity is over twice the size of the Cadillac's 500 CID 8.2 L V8 engine
V8 engine
A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft....

, which was considered the largest engine of its type in the 1970s. These engines ran at very low rpm, often less than 1,500 rpm maximum, and had a specific output of about 10 hp/L. The US tractor industry both farm and industrial relied on large four-cylinder power units until the early 1960s, when six-cylinder designs came into favor. International Harvester built a large 5.7 litre (350 CID) four-cylinder for their WD-9 series tractors.

Other technologically or historically notable engines using this configuration include:
  • Alfa Romeo Twin Cam engine
    Alfa Romeo Twin Cam engine
    The all alloy Alfa Romeo Twin Cam engine series was an inline-4 cylinder engine produced by Alfa Romeo from 1954 to 1994. For earlier Alfa Romeo engines featuring twin camshafts, refer to the main Alfa Romeo page...

     - one of the first mass-produced twin cam engines produced from 1954. Also first engine in production car with variable valve timing
    Variable valve timing
    In internal combustion engines, variable valve timing , also known as Variable valve actuation , is a generalized term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine...

    .
  • BMC A-Series engine
    BMC A-Series engine
    Austin Motor Company's small straight-4 automobile engine, the A-Series, is one of the most common in the world. Launched in 1951 with the Austin A30, production lasted until 2000 in the Mini. It used a cast-iron block and cylinder head, and a steel crankshaft with 3 main bearings...

     - the first engine to be used in a transverse drive train powering the front wheels of a mass-produced automobile (Mini
    Mini
    The Mini is a small car that was made by the British Motor Corporation and its successors from 1959 until 2000. The original is considered a British icon of the 1960s, and its space-saving front-wheel-drive layout influenced a generation of car-makers...

    ).
  • Chevrolet
    Chevrolet
    Chevrolet , also known as Chevy , is a brand of vehicle produced by General Motors Company . Founded by Louis Chevrolet and ousted GM founder William C. Durant on November 3, 1911, General Motors acquired Chevrolet in 1918...

     Cosworth
    Cosworth
    Cosworth is a high performance engineering company founded in London in 1958, specialising in engines and electronics for automobile racing , mainstream automotive and defence industries...

     Twin-Cam Vega
    Chevrolet Vega
    The Chevrolet Vega is a subcompact, two-door automobile that was produced by the Chevrolet division of General Motors for the 1971-1977 model years. Named after the star Vega, the car was powered by a lightweight aluminum-block inline four-cylinder engine...

     - 2.0 L all aluminum (block & head), DOHC, 16 valves, electronic fuel injection, stainless steel header.
  • Dodge
    Dodge
    Dodge is a United States-based brand of automobiles, minivans, and sport utility vehicles, manufactured and marketed by Chrysler Group LLC in more than 60 different countries and territories worldwide....

     A853 - intercooled turbo engine from the SRT-4
    Dodge SRT-4
    The Dodge SRT-4 is a sport compact car manufactured by Dodge from 2003-2005. A turbocharged variant of the Neon, the car was developed by DaimlerChrysler's in house PVO tuner group. PVO was officially renamed SRT in 2004. The "4" in the SRT-4's name denotes the number of cylinders of the engine...

    , set the land speed record for 4-cylinder production cars at the Bonneville Salt Flats.
  • Fiat Twin Cam engine
    Fiat Twin Cam engine
    Designed by Aurelio Lampredi the Fiat Twin Cam was an advanced inline-4 automobile engine produced from 1959 through 1994 as a Fiat/Lancia engine until it was replaced by the "family B" series of engines...

     - One of the first mass-produced twincam engines, produced from 1959.
  • Ford Model T engine
    Ford Model T engine
    The Ford Model T used a 177-cubic-inch inline 4-cylinder engine. It was primarily a petrol engine, but it had multifuel ability and could also burn kerosene or ethanol. It produced for a top speed of . The engine had side valves and 3 main bearings and was built in-unit with the Model T's novel...

     - one of the most widely produced engines in the world.
  • GM Quad-4 engine
    GM Quad-4 engine
    The engine family known as the Quad 4 was debuted to the public in the spring of 1987. The Quad 4 was a DOHC inline 4-cylinder produced by General Motors' Oldsmobile division...

     - twin-cam Oldsmobile engine offered in GM small, sporty cars.
  • Honda ED engine - first use of Honda's CVCC
    CVCC
    CVCC is a trademark by the Honda Motor Company for an engine with reduced automotive emissions, which stood for "Compound Vortex Controlled Combustion". This technology allowed Honda's cars to meet United States emission standards in the 1970s without a catalytic converter...

     technology.
  • Honda F20C engine
    Honda F20C engine
    The F20C and F22C1 are inline-4 engines produced by Honda. They are one of the few Honda 4-cylinder automobile engines that are designed to sit longitudinally for rear wheel drive....

     - its 240 hp from 2.0 L was the highest specific output of its time, particularly noteworthy in that it achieved this without forced induction
    Forced induction
    Forced induction is the process of compressing air on the intake of an internal combustion engine . A forced induction engine uses a gas compressor to increase the pressure, temperature and density of the air...

    .
  • Mitsubishi Sirius engine
    Mitsubishi Sirius engine
    The Mitsubishi Sirius or 4G6/4D6 engine is the name of one of Mitsubishi Motors' four series of inline 4 automobile engines, along with Astron, Orion, and Saturn. The 4G6 are gasoline engines, the 4D6 diesels.-4G61:...

     - includes the 4G63, which has the highest specific output of a turbocharged production engine in the world with the Lancer Evolution FQ-400 available in the United Kingdom (202.9 hp/L)
  • GM Iron Duke engine
    GM Iron Duke engine
    Iron Dukes were fitted with fuel injection in 1982. This version was christened the Tech IV, though Car and Driver later ridiculed it as the low-Tech IV. Power output remained at ....

     - A versatile 151 CID 2.5 L 95 hp engine used in many GM cars in longitudinal configuration powering rear wheels or a transverse configuration powering front wheels or rear wheels. "Super Duty" racing versions of the Iron Duke were developed by Pontiac Racing.
  • Triumph Slant-4 engine
    Triumph Slant-4 engine
    The Triumph Slant-4 is an engine developed by Triumph. According to Triumph historians Graham Robson and Richard Langworth in Triumph Cars, the complete story, the engine was developed in-house by a design team led by Lewis Dawtry and Harry Webster....

     - the first mass-produced multi-valve
    Multi-valve
    In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and can operate at higher revolutions per minute than a two-valve engine, delivering more power.- Multi-valve rationale :A multi-valve design...

     engine for Triumph
    Triumph Motor Company
    The Triumph Motor Company was a British car and motor manufacturing company. The Triumph marque is owned currently by BMW. The marque had its origins in 1885 when Siegfried Bettmann of Nuremberg initiated S. Bettmann & Co and started importing bicycles from Europe and selling them with his own...

     and an early turbo engine for Saab
    Saab Automobile
    Saab Automobile AB, better known as Saab , is a Swedish car manufacturer owned by Dutch automobile manufacturer Swedish Automobile NV, formerly Spyker Cars NV. It is the exclusive automobile Royal Warrant holder as appointed by the King of Sweden...

    .
  • Willys L-134 engine
    Willys Go Devil engine
    The Willys L134 was a straight-4 automobile engine made famous in the Jeep produced in World War II. The engine displaced with a bore and stroke, a very undersquare design. It was an L-head design, with valves parallel to the cylinders...

     - nicknamed the Go Devil engine. Powered the World War II Jeep
    Willys MB
    The Willys MB US Army Jeep and the Ford GPW, were manufactured from 1941 to 1945. These small four-wheel drive utility vehicles are considered the iconic World War II Jeep, and inspired many similar light utility vehicles. Over the years, the World War II Jeep later evolved into the "CJ" civilian...

     and post-war models. Notably undersquare, with 3.125 in (79.4 mm) bore and 4.375 in (111.1 mm) stroke.


In the late 2000s, with auto manufacturers making efforts to increase fuel efficiency and reduce emissions, due to the high price of oil and the economic recession, the proportion of new vehicles with inline-four engines have increased considerably at the expense of V6 and V8 engines. This is particularly evident in mid-size vehicles where a decreasing number of buyers have chosen the V6 performance options.

Racing use

1913 saw a Peugeot
Peugeot
Peugeot is a major French car brand, part of PSA Peugeot Citroën, the second largest carmaker based in Europe.The family business that precedes the current Peugeot company was founded in 1810, and manufactured coffee mills and bicycles. On 20 November 1858, Emile Peugeot applied for the lion...

 driven by Jules Goux
Jules Goux
Jules Goux, born Valentigney 6 April 1885 - died Valentigney 6 March 1965, was a Grand Prix motor racing champion and the first Frenchman, and the first European, to win the Indianapolis 500.-Biography:...

 winning the Indianapolis 500
Indianapolis 500
The Indianapolis 500-Mile Race, also known as the Indianapolis 500, the 500 Miles at Indianapolis, the Indy 500 or The 500, is an American automobile race, held annually, typically on the last weekend in May at the Indianapolis Motor Speedway in Speedway, Indiana...

. This car was powered by an inline-four engine designed by Ernest Henry. This design was very influential for racing engines as it featured for the first time dual overhead camshafts (DOHC) and four valve
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...

s per cylinder, a layout that would become the standard until today for racing inline-four engines.

This Peugeot was sold to the American driver "Wild Bob" Burman
Bob Burman
Bob Burman was an American racecar driver active in the formative years of auto racing.-Biography:He was born on April 23, 1884 in Imlay City, Michigan. He was the winner of the Prest-O-Lite Trophy Race in 1909. He competed at the inaugural Indianapolis 500 in 1911...

 who broke the engine in 1915. As Peugeot couldn't deliver a new engine during World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, Burman asked Harry Arminius Miller
Harry Arminius Miller
Harry Arminius Miller was an influential and famous American race car builder, most active in the 1920s and 1930s...

 to build a new engine. With John Edward and Fred Offenhauser
Fred Offenhauser
Fred Offenhauser , was an automotive engineer and mechanic who designed the Offenhauser racing engine, nicknamed the "Offy", which dominated competition in the Indianapolis 500 race for decades....

, Miller created a Peugeot-inspired inline-four engine. This was the first version of the engine that would dominate the Indianapolis 500 until 1976 under the brand Miller and later Offenhauser
Offenhauser
Offenhauser was an American racing engine manufacturer that operated from 1933 to 1983.The Offenhauser engine, familiarly known as the "Offy", was developed by Fred Offenhauser and his employer Harry Arminius Miller, after maintaining and repairing a 1913 Peugeot Grand Prix car of the type which...

. The Offenhausers won five straight victories at Indianapolis from 1971 to 1976, and it was not until 1981 that they were eliminated as competitors by engines such as the Cosworth
Cosworth
Cosworth is a high performance engineering company founded in London in 1958, specialising in engines and electronics for automobile racing , mainstream automotive and defence industries...

 V8 engine
V8 engine
A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft....

.

Many cars produced for the pre-WWII
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 voiturette
Voiturette
Voiturette is a word mostly used to describe a miniature automobile; however, it has several nuanced meanings, depending largely on the usage date.-History:...

 Grand Prix motor racing
Grand Prix motor racing
Grand Prix motor racing has its roots in organised automobile racing that began in France as far back as 1894. It quickly evolved from a simple road race from one town to the next, to endurance tests for car and driver...

 category used inline-four engine designs. 1.5 L supercharged
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...

 engines found their way into cars such as the Maserati 4CL and various English Racing Automobiles
English Racing Automobiles
English Racing Automobiles was a British racing car manufacturer active from 1933 to 1954. Currently the ERA trademark is owned by a British kit-car manufacturer.-Prewar history:...

 (ERA) models. These were resurrected after the war, and formed the foundation of what was later to become Formula One
Formula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

, although the straight-eight supercharged Alfettas would dominate the early years of F1.

Another engine that played an important role in racing history is the inline-four Ferrari
Ferrari
Ferrari S.p.A. is an Italian sports car manufacturer based in Maranello, Italy. Founded by Enzo Ferrari in 1929, as Scuderia Ferrari, the company sponsored drivers and manufactured race cars before moving into production of street-legal vehicles as Ferrari S.p.A. in 1947...

 engine designed by Aurelio Lampredi
Aurelio Lampredi
Aurelio Lampredi was an Italian automobile and aircraft engine designer.Born in Livorno, he began his career at Piaggio, makers of the Vespa scooter, but quickly moved up to larger engines...

. This engine was originally designed as a 2 L Formula 2 engine for the Ferrari 500, but evolved to 2.5 L to compete in Formula One
Formula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

 in the Ferrari 625. For sports car
Sports car
A sports car is a small, usually two seat, two door automobile designed for high speed driving and maneuverability....

 racing, capacity was increased up to 3.4 L for the Ferrari 860 Monza.

Yet another very successful engine was the Coventry Climax
Coventry Climax
Coventry Climax was a British forklift truck, fire pump, and speciality engine manufacturer.-History:The company was started in 1903 as Lee Stroyer, but two years later, following the departure of Stroyer, it was relocated to Paynes Lane, Coventry, and renamed to Coventry-Simplex by H...

 inline-four originally designed by Walter Hassan
Walter Hassan
Walter Hassan OBE, C.Eng., M.I. Mech.E. was a distinguished UK automotive engineer who took part in the design and development of three very successful engines: Jaguar XK, Coventry Climax and Jaguar V12 as well as the ERA racing car....

 as a 1.5 L Formula 2 engine. Enlarged to 2.0 L for Formula One in 1958, it evolved into the large 2495 cc FPF that won the Formula One championship in Cooper
Cooper Car Company
The Cooper Car Company was founded in 1946 by Charles Cooper and his son John Cooper. Together with John's boyhood friend, Eric Brandon, they began by building racing cars in Charles' small garage in Surbiton, Surrey, England in 1946...

's chassis in 1959 and 1960.

In formula One, the 1980s were dominated by the 1500 cc turbocharged cars. The BMW model M12/13 turbo was notable for the era for its high boost pressures and performance. The cast iron block 4-cylinder turbocharged Formula One motor, based on the standard BMW M10 engine introduced in 1961, powered the F1 cars of Brabham, Arrows and Benetton and won the world championship in 1983. In the years 1986 and 1987, the version M12/13/1 was tilted sideways by 72° for use in the extremely low Brabham BT55
Brabham BT55
The Brabham BT55 was a Formula One racing car designed by Gordon Murray and David North for the Brabham team owned by Bernie Ecclestone. It used a BMW four-cylinder turbocharged engine tilted over on its side to allow a clear supply of air to the rear wing. The car competed during the 1986 Formula...

, unfortunately the design was not successful, probably due to cooling issues in the tight compartment. The 1986 engine was said to produce about 1300 hp in qualifying.

Motorcycle use

For racing, Honda built inline-four engines as small as a 125 cc for the Honda 125/4. This engine was replaced by a 125 cc straight-five engine. The largest proprietary inline-four engine in a commercially produced motorcycle is the 1402 cc engine in the Suzuki GSX1400
Suzuki GSX1400
The GSX1400 was a Suzuki muscle bike standard motorcycle, made from 2001–2007, as a faster and more powerful premium offering, upmarket in relation to Suzuki's similar Bandit 1200. The GSX1400 was characterized as a "disco-era", "seventies-style metal mountain", but loaded with the latest...

.

Modern inline-four motorcycle engines first gained their popularity with Honda
Honda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...

's SOHC CB750
Honda CB750
The Honda CB750 is a motorcycle built in several model series between 1969 and 2003 and 2007 that is recognized as a milestone for Honda's successful introduction of a transverse, overhead camshaft inline four-cylinder engine that has ever since been the dominant sport bike configuration...

 in the 1970s. Since then, the inline-four has become one of the most common engine configurations in street bikes. Outside of the cruiser
Cruiser (motorcycle)
Cruiser is the term for motorcycles that mimic the design style of American machines from the 1930s to the early 1960s, including those made by Harley-Davidson, Indian, Excelsior and Henderson. The market for models evocative of the early cruisers has grown to embrace 60 percent of the U.S...

 category, the inline-four is simply the most common configuration because of its relatively high performance-to-cost ratio. All of the Japanese motorcycle manufacturers offer motorcycles with inline-four engines, as does MV Agusta
MV Agusta
MV Agusta is a motorcycle manufacturer founded in 1945 near Milan in Cascina Costa, Italy. The company began as an offshoot of the Agusta aviation company formed by Count Giovanni Agusta in 1923. The Count died in 1927, leaving the company in the hands of his wife and sons, Domenico, Vincenzo,...

 and BMW
BMW motorcycles
BMW's motorcycle history began in 1921 when the company commenced manufacturing engines for other companies. Motorcycle manufacturing now operates under the BMW Motorrad brand...

 who employ both longitudinal
Longitudinal engine
In automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....

 and transverse
Transverse engine
A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...

-mounted engines. Even the modern Triumph
Triumph Motorcycles Ltd
Triumph Motorcycles Ltd is the largest surviving British motorcycle manufacturer, which was established in 1984 by John Bloor after the original manufacturer Triumph Engineering went into receivership...

 company has offered inline-four-powered motorcycles, though they were discontinued in favour of a triple
Triumph Triple
Triumph Triple is an inline three-cylinder motorcycle engine manufactured by the Triumph Motorcycle Company. It has received credit for "bringing Triumph back from the grave"....

.

The 2009 Yamaha R1 has an interesting inline-four engine that does not fire at even intervals of 180°. Instead, it uses a crossplane
Crossplane
The crossplane or cross-plane is a crankshaft design for V8 engines with a 90° angle between the cylinder banks.The crossplane crankshaft has four crankpins, each offset at 90° from the adjacent crankpins...

crankshaft that prevents the pistons from simultaneously reaching top dead centre. This results in increased torque at lower engine speeds.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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