The Inline-four engine or Straight-four engine is an internal combustion engine The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber. In an internal combustion engine the expansion of the high temperature and pressure gases, which are produced by the combustion, directly applies force to a movable component of the engine, such as the with all four cylinders A cylinder is the central working part of a reciprocating engine, 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 precision features are machined into it. The cylinders may then be lined with sleeves or liners of some mounted in a straight line, or plane along the crankcase In an internal combustion engine, the crankcase is the housing for the crankshaft. The enclosure forms the largest cavity in the engine and is located below the cylinder block. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the pistons A piston is a component of reciprocating engines, pumps and gas compressors. It is located in a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from driving a common crankshaft The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation. To convert the reciprocating motion into rotation, the crankshaft has "crank throws" or "crankpins", additional bearing surfaces whose axis is offset from that of the crank, to. 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 the simplest design which is in perfect primary balance Engine balance is the design, construction and tuning of an engine to run smoothly. Engine balance reduces vibration and other stresses, and may improve the performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress on other machinery near the engine and confers a degree of mechanical simplicity which makes it popular for economy cars.[1] 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.

Contents

Displacement

This inline engine configuration is the most common in cars An automobile, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor. Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for one to eight people, to typically have four wheels, and to be constructed principally for the with a 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 (BDC). It is commonly specified in cubic centimeters (cc), litres (l), or (mainly in North America) cubic inches (CID). Motive power output of a combustion engine is 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 Automobil Holding SE, usually shortened to Porsche SE , a Societas Europaea or European Public Company, is a German automotive manufacturer of luxury high performance automobiles, which is majority-owned by the Piëch and Porsche families. Porsche SE is headquartered in Zuffenhausen, a city district of Stuttgart, Baden-Württemberg used a 3.0 L four in its 944 S2 The 944 is a sports car built by Porsche between 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, which replaced the 944. The 944 was a successful model and 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. The 968 became the final model in an evolving line, starting almost 20 years earlier with the introduction of the Porsche 924 and ending with the Turbo S, Turbo RS, and sports cars, and Rolls Royce produced several 4-cylinder engines of 2,838 cc with basic cylinder dimensions of 3.5 in (89 mm) diameter and 4.5 in (110 mm) stroke (Rolls Royce B40);

Classic and Antique vehicles tended to have larger displacements to develop horsepower and torque. The Model A Ford was built with a 3.3 L inline-four engine.

Four-cylinder diesel engines, which are lower revving than gasoline engines, often exceed 3.0 L. Mitsubishi still employs a 3.2 L four-cylinder 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. As with any turbocharged engine, turbodiesels can offer higher specific power outputs, lower emissions levels, improved efficiency and higher refinement levels than their naturally aspirated in its Pajero (called the Shogun or Montero in certain markets), and Tata Motors employs a 3.0 L four-cylinder diesel in its Spacio and Sumo Victa.

The Toyota B engine series of diesel engines varies in displacement from 3.0- 4.1 L. The largest engine in that series was used in the Mega Cruiser.

Larger four-cylinder 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 engines 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 during the final stage of compression. This is in contrast to spark ignition engines such as a petrol engine (known as a gasoline engine in North America) or gas engine (using a for stationary, marine and locomotive A Diesel locomotive is a type of railroad locomotive in which the prime mover is a Diesel engine. Several types have been developed, the principal distinction being in the means by which the prime mover's mechanical power is conveyed to the driving wheels use (which run at low speeds) are made in much larger sizes.

Displacement can also be very small, as found in kei cars Kei car, K-car, or keijidōsha (pronounced /keːdʑidoːɕa/), is a Japanese category of small automobiles, including passenger cars, vans, and pickup trucks. They are designed to exploit local tax and insurance relaxations, and in more rural areas are exempted from the requirement to certify that adequate parking is available for the vehicle sold in Japan, such as the Subaru EN series; engines that started out at 550 cc and are currently at 660 cc, with variable valve timing, DOHC Overhead camshaft, commonly abbreviated to OHC, valvetrain configurations place the engine camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters in a more direct manner compared to overhead valves and pushrods and superchargers resulting in engines that produce 65 PS (48 kW; 64 bhp).

Balance and smoothness

Computer generated image showing the major internal moving parts of an inline-four engine with belt-driven double overhead camshafts and 4 valves per cylinder.

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 is the design, construction and tuning of an engine to run smoothly. Engine balance reduces vibration and other stresses, and may improve the performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress on other machinery near the engine 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.[2]

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 shafts In piston engine engineering, a balance shaft is an eccentric weighted shaft which offsets vibrations in engine designs that are not inherently balanced . They were first invented and patented by British engineer Frederick Lanchester in 1904 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 Corporation is the sixth largest automaker in Japan and the seventeenth largest in the world by global vehicle production. It is part of the Mitsubishi keiretsu, formerly the biggest industrial group in Japan, and was formed in 1970 from the automotive division of Mitsubishi Heavy Industries. The company has its headquarters in 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.[3] However, in the past, there were numerous examples of larger inline-fours without balance shafts, such as the Citroën DS 23 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, the DS is known for its aerodynamic futuristic body design and innovative technology, including a hydropneumatic self-levelling suspension 2,347 cc engine that was a derivative of the Traction Avant The Citroën Traction Avant was an innovative front wheel drive automobile produced by the French manufacturer Citroën. About 760,000 units were produced from 1934 to 1957 engine, the 1948 Austin The Austin Motor Company was a British manufacturer of automobiles. The trademark is currently owned by Nanjing Automitive 2,660 cc engine used in the Austin-Healey 100 and Austin Atlantic, the 3.3 L flathead engine A flathead engine or sidevalve 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. The design was common on early engine designs, but has since fallen from use used in the Ford Model A (1927) The Ford Model A 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. This new Model A (a previous model had used the Model A name back in 1903–1904) was designated as, and the 2.5 L GM Iron Duke engine The Iron Duke was a 2.5 L (150.8 cu in) I4 piston engine. All Iron Dukes were built by Pontiac beginning in 1977 and ending in 1993 used in a number of American cars and trucks. Soviet/Russian GAZ Volga cars and UAZ UAZ , Ulyanovsky Avtomobilny Zavod (Ульяновский Автомобильный Завод) is an automobile manufacturer based in Ulyanovsk, Russia which makes SUVs, buses and trucks. Production started in 1941 SUVs, vans and light trucks used aluminium Aluminium (UK: /ˌæljʉˈmɪniəm/ AL-yew-MIN-ee-əm) or aluminum (US: /əˈluːmɨnəm/ ( listen) ə-LOO-mi-nəm) 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. Aluminium is the most abundant metal in the Earth's crust, 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.[4]

Four cylinder engines also have a smoothness problem in that the power strokes of the pistons do not overlap. With four cylinders and four cycles to complete, 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.

Automobile use

Notable production inline-four engines

Ford Model T The Ford Model T is an automobile that was produced by Henry Ford's Ford Motor Company from 1908 through 1927. The Model T set 1908 as the historic year that the automobile became popular. It is generally regarded as the first affordable automobile, the car that opened travel to the common middle-class American; some of this was because of Ford's engine

The smallest Automobiles are frequently judged in their industry by many superlatives: the smallest, largest, fastest, lightest, best-selling, and so on. They vary greatly in size, engine displacement, power, price, and many other traits automobile production inline-four engine powered the 1961 Mazda P360 Carol The R360 was replaced in 1961 with the Mazda P360 Carol, the company's first 4-passenger car. It was larger than the Mazda R360 it replaced, running on a 193 cm wheelbase for a total length of 298 cm. It used a rear-mounted water-cooled 358 cc 4-cylinder OHV engine, which is one of the smallest 4-cylinder automobile engines in history kei car Kei cars, K-cars, or keijidōsha (pronounced /keːdʑidoːɕa/), are a Japanese category of small vehicles, including passenger cars, vans, and pickup trucks. They are designed to exploit local tax and insurance regulations, and in most rural areas are exempted from the requirement to certify that adequate parking is available for the vehicle. Displacing just 358 cc, the Mazda OHV was a conventional but tiny pushrod An overhead valve engine, also informally called pushrod engine or I-head engine, is a type of piston engine that places the camshaft within the cylinder block (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine), and uses pushrods or rods to actuate rocker arms above the engine. Honda produced, from 1963-1967, a 356 cc (21.7 cu in) inline-four engine for the T360 The T360 was a pickup truck from Honda. Introduced in June 1963, it was Honda's first production automobile truck. Inline-four motorcycle engines are built down to 250 cc, e.g. in the Honda CBR250.

Most inline-four engines, however, have been over 700 cc (43 cu in) displacement. A practical upper limit could be placed in the 2.5 L range for contemporary production cars. Larger engines (up to 4.5 L) have been seen in racing and light truck A truck or lorry (British English) is a motor vehicle designed to transport cargo. They vary greatly in size, power and configuration, with the smallest being mechanically similar to an automobile. Commercial trucks can be very large and powerful, and may be configured to mount specialized equipment, such as in the case of fire trucks and concrete use, especially using diesel fuel Diesel fuel in general is any liquid fuel used in diesel engines. The most common is a specific fractional distillate of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid (BTL) or gas to liquid (GTL) diesel, are increasingly being developed and adopted. To distinguish these types, (such as the Mercedes-Benz MBE 904). The use of balance shafts allowed Porsche Porsche Automobil Holding SE, usually shortened to Porsche SE , a Societas Europaea or European Public Company, is a German automotive manufacturer of luxury high performance automobiles, which is majority-owned by the Piëch and Porsche families. Porsche SE is headquartered in Zuffenhausen, a city district of Stuttgart, Baden-Württemberg to use a 3.0 L (2990 cc) inline-four engine on road cars first in the 944 S2 The 944 is a sports car built by Porsche between 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, which replaced the 944. The 944 was a successful model, but the largest modern non-diesel was the plain 3,188 cc (194.5 cu in) 195 in the 1961 Pontiac Tempest The Pontiac Tempest was an entry-level compact automobile produced by the Pontiac Motor Division of General Motors, introduced in September 1960 for the 1961 model year. It shared the new monocoque Y platform with the Buick Special and Skylark, and Oldsmobile F-85 and Cutlass. It also appeared under the LeMans nameplate largely beginning with the 1.

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 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 Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts (138 kW The watt is a derived unit of power in the International System of Units (SI), named after the Scottish engineer James Watt (1736–1819). The unit measures the rate of energy conversion. It is defined as one joule per second) at 5600 rpm and 195 ft·lbf (263 N·m) 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 (75 kW), 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 17,000 cc engine. Its cubic capacity is over twice the size of the Cadillac's 500 CID A cubic inch is a non-SI unit of volume, equal to the volume of a cube with sides of one inch 8.2 L 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:

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