Straight-four engine

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Diagram of a DOHC straight-four engine Engine movingparts.jpg
Diagram of a DOHC straight-four engine
1989-2006 Ford I4 DOHC engine with the cylinder head removed Ford-I4DOHC-engblock.jpeg
1989-2006 Ford I4 DOHC engine with the cylinder head removed
2006-2009 Nissan M9R diesel engine Nissan M9R Engine 03.JPG
2006-2009 Nissan M9R diesel engine

A straight-four engine (also called an inline-four) is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.

Contents

The majority of automotive four-cylinder engines use a straight-four layout [1] : pp. 13–16  (with the exceptions of the flat-four engines produced by Subaru and Porsche) [2] and the layout is also very common in motorcycles and other machinery. Therefore the term "four-cylinder engine" is usually synonymous with straight-four engines. When a straight-four engine is installed at an inclined angle (instead of with the cylinders oriented vertically), it is sometimes called a slant-four.

Between 2005 and 2008, the proportion of new vehicles sold in the United States with four-cylinder engines rose from 30% to 47%. [3] [4] By the 2020 model year, the share for light-duty vehicles had risen to 59%. [5]

Design

A four-stroke straight-four engine always has a cylinder on its power stroke, unlike engines with fewer cylinders where there is no power stroke occurring at certain times. Compared with a V4 engine or a flat-four engine, a straight-four engine only has one cylinder head, which reduces complexity and production cost.

Displacement

Petrol straight-four engines used in modern production cars typically have a displacement of 1.3–2.5 L (79–153 cu in), but larger engines have been used in the past, for example the 1927–1931 Bentley 4½ Litre.

Diesel engines have been produced in larger displacements, such as a 3.2 L turbocharged Mitsubishi engine (used the Pajero/Shogun/Montero SUV) and a 3.0 L Toyota engine. European and Asian trucks with a gross vehicle weight rating between 7.5 and 18 tonnes typically use inline four-cylinder diesel engines with displacements around 5 litres. [6] [7] [8] [9] [10] [11] [12] Larger displacements are found in locomotive, marine and stationary engines.

Displacement can also be very small, as found in kei cars sold in Japan. Several of these engines had four cylinders at a time when regulations dictated a maximum displacement of 550 cc; the maximum size is currently at 660 cc.

Primary and secondary balance

Straight-four engines with the preferred crankshaft configuration have perfect primary balance. [1] : p. 12  This is 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, straight-four engines have a secondary imbalance. This is caused by the acceleration/deceleration of the pistons during the top half of the crankshaft rotation being greater than that of the pistons in the bottom half of the crankshaft rotation (because the connecting rods are not infinitely long). 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 common among all piston engines, but the effect is particularly strong on four-stroke inline-four because of the two pistons always moving together.

The strength of this imbalance is determined by the reciprocating mass, the ratio of connecting rod length to stroke, and the peak piston velocity. Therefore, small displacement engines with light pistons show little effect, and racing engines use long connecting rods. However, the effect grows quadratically with engine speed (rpm).

Pulsations in power delivery

Animation of an Inline-four engine Reihenmotor Vier Zylinder 1-2-4-3.gif
Animation of an Inline-four engine

Four-stroke engines with five or more cylinders are able to have at least one cylinder performing its power stroke at any given point in time. However, four-cylinder engines have gaps in the power delivery, since each cylinder completes its power stroke before the next piston starts a new power stroke. This pulsating delivery of power results in more vibrations than engines with more than four cylinders.

Usage of balance shafts

A balance shaft system is sometimes used to reduce the vibrations created by a straight-four engine, most often in engines with larger displacements. The balance shaft system was invented in 1911 and consists of two shafts carrying identical eccentric weights that rotate in opposite directions at twice the crankshaft's speed. [1] : pp. 42–44  This system was patented by Mitsubishi Motors in the 1970s and has since been used under licence by several other companies. [13] [14]

Not all large displacement straight-four engines have used balance shafts, however. Examples of relatively large engines without balance shafts include the 2.4 litre Citroën DS engine, the 2.6 litre Austin-Healey 100 engine, the 3.3 L Ford Model A (1927) engine and the 2.5 L GM Iron Duke engine. Soviet/Russian GAZ Volga and UAZ engines with displacements of up to 2.9 litres were produced without balance shafts from the 1950s to the 1990s, however these were relatively low-revving engines which reduces the need for a balance shaft system. [1] : pp. 40–44 

Usage in production cars

1908-1941 Ford Model T engine Fordsidevalve.jpg
1908–1941 Ford Model T engine
1970 Alfa Romeo Twin Cam engine Alfa Romeo 1750 GTV engine.jpg
1970 Alfa Romeo Twin Cam engine

Most modern straight-four engines used in cars have a displacement of 1.5–2.5 L (92–153 cu in). The smallest automotive straight-four engine was used in the 1963–1967 Honda T360 kei truck and has a displacement of 356 cc (21.7 cu in), while the largest mass-produced straight-four car engine is the 1999–2019 Mitsubishi 4M41 diesel engine which was used in the Mitsubishi Pajero and has a displacement of 3.2 L (195 cu in). [15] [16]

Significant straight-four car engines include:

Usage in racing cars

1980s BMW M12/13 Formula One engine BMW F1 Engine M12 M13.JPG
1980s BMW M12/13 Formula One engine

Many early racing cars used straight-four engines, however the Peugeot engine which won the 1913 Indianapolis 500 was a highly influential engine. Designed by Ernest Henry, this engine had double overhead camshafts (DOHC) with four valves per cylinder, a layout that would become the standard until today for racing inline-four engines. [19] : pp. 14–17 

Amongst the engines inspired by the Peugeot design was the Miller engine, which was a successful racing engine through the 1920s and early 1930s. The Miller engine evolved into the Offenhauser engine which had a highly successful spanning from the 1933 until 1981, including five straight victories at the Indianapolis 500 from 1971 to 1976. [19] : pp. 182–185 

Many cars produced for the pre-WWII voiturette Grand Prix motor racing category used inline-four engine designs. 1.5 L supercharged engines found their way into cars such as the Maserati 4CL and various English Racing Automobiles (ERA) models. These were resurrected after the war, and formed the foundation of what was later to become Formula One, 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 straight-four Ferrari engine designed by Aurelio Lampredi. 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 in the Ferrari 625. [19] : pp. 78–81, 86–89  For sports car racing, capacity was increased up to 3.4 L for the Ferrari 860 Monza.

The Coventry Climax straight-four engine was also a very successful racing engine, which began life as a 1.5 litre Formula 2 engine. Enlarged to 2.0 litres for Formula One in 1958, it evolved into the large 2,495 cc FPF that won the Formula One championship in Cooper's chassis in 1959 and 1960. [19] : pp. 130–133 

In Formula One, the 1980s were dominated by the 1,500 cc turbocharged cars. The BMW M12/13 engine was notable for the era for its high boost pressures and performance. The cast iron block was based on a standard road car block and powered the F1 cars of Brabham, Arrows and Benetton and won the world championship in 1983. The 1986 version of the engine was said to produce about 1,300 hp (969 kW) in qualifying trim. [20]

Usage in motorcycles

1970 Honda CB750 engine Honda CB750 Engine.jpg
1970 Honda CB750 engine

Belgian arms manufacturer FN Herstal, which had been making motorcycles since 1901, began producing the first motorcycles with inline-fours in 1905. [21] The FN Four had its engine mounted upright with the crankshaft longitudinal. Other manufacturers that used this layout included Pierce, Henderson, Ace, Cleveland, and Indian in the United States, Nimbus in Denmark, Windhoff in Germany, and Wilkinson in the United Kingdom. [22]

The first across-the-frame 4-cylinder motorcycle was the 1939 racer Gilera 500 Rondine, it also had double-over-head camshafts, forced-inducting supercharger and was liquid-cooled. [23] Modern inline-four motorcycle engines first became popular with Honda's SOHC CB750 introduced in 1969, and others followed in the 1970s. Since then, the inline-four has become one of the most common engine configurations in street bikes. Outside of the cruiser category, the inline-four is the most common configuration because of its relatively high performance-to-cost ratio.[ citation needed ] All major Japanese motorcycle manufacturers offer motorcycles with inline-four engines, as do MV Agusta and BMW. BMW's earlier inline-four motorcycles were mounted horizontally along the frame, but all current four-cylinder BMW motorcycles have transverse engines. The modern Triumph company has offered inline-four-powered motorcycles, though they were discontinued in favour of triples.

The 2009 Yamaha R1 has an inline-four engine that does not fire at even intervals of 180°. Instead, it uses a crossplane crankshaft that prevents the pistons from simultaneously reaching top dead centre. This results in better secondary balance, which is particularly beneficial in the higher rpm range, and "big-bang firing order" theory says the irregular delivery of torque to the rear tire makes sliding in the corners at racing speeds easier to control.

Inline-four engines are also used in MotoGP by the Suzuki (since 2015) and Yamaha (since 2002) teams. In 2010, when the four-stroke Moto2 class was introduced, the engines for the class were a 600 cc (36.6 cu in) inline-four engine made by Honda based on the CBR600RR with a maximum power output of 110 kW (150 hp). Starting in 2019, the engines were replaced by a Triumph 765 cc (46.7 cu in) triple engine.

Usage in light and medium duty commercial vehicles

Inline-four engines are also used in light duty commercial vehicles such as Karsan Jest and Mercedes-Benz Sprinter.

See also

Related Research Articles

<span class="mw-page-title-main">Reciprocating engine</span> Engine utilising one or more reciprocating pistons

A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.

<span class="mw-page-title-main">V6 engine</span> Piston engine with six cylinders in a "V" configuration

A V6 engine is a six-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.

<span class="mw-page-title-main">Radial engine</span> Reciprocating engine with cylinders arranged radially from a single crankshaft

The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is called a "star engine" in some other languages.

<span class="mw-page-title-main">V10 engine</span> Piston engine with ten cylinders in V configuration

A V10 engine is a ten-cylinder piston engine where two banks of five cylinders are arranged in a V configuration around a common crankshaft. V10 engines are much less common than V8 and V12 engines. Several V10 diesel engines have been produced since 1965, and V10 petrol engines for road cars were first produced in 1991 with the release of the Dodge Viper.

<span class="mw-page-title-main">V4 engine</span> Piston engine with four cylinders in "V" configuration

A V4 engine is a four-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.

<span class="mw-page-title-main">Flat-four engine</span> Horizontally opposed four-cylinder piston engine

A flat-four engine, also known as a horizontally opposed-four engine or boxer engine, is a four-cylinder piston engine with two banks of cylinders lying on opposite sides of a common crankshaft. The most common type of flat-four engine is the boxer-four engine, each pair of opposed pistons moves inwards and outwards at the same time.

<span class="mw-page-title-main">Straight-twin engine</span> Inline piston engine with two cylinders

A straight-twin engine, also known as an inline-twin, vertical-twin, or parallel-twin, is a two-cylinder piston engine whose cylinders are arranged in a line along a common crankshaft.

<span class="mw-page-title-main">Straight-six engine</span> Internal combustion engine

The inline-six engine is a piston engine with six cylinders arranged in a straight line along the crankshaft. A straight-six engine has perfect primary and secondary engine balance, resulting in fewer vibrations than other designs of six or fewer cylinders.

The straight-five engine is a piston engine with five cylinders mounted in a straight line along the crankshaft.

<span class="mw-page-title-main">Engine displacement</span> Volume swept by all of the pistons

Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. It is commonly used as an expression of an engine's size, and by extension as an indicator of the power an engine might be capable of producing and the amount of fuel it should be expected to consume. For this reason displacement is one of the measures often used in advertising, as well as regulating, motor vehicles.

<span class="mw-page-title-main">Straight-three engine</span> Type of engine

A straight-three engine is a three-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.

<span class="mw-page-title-main">U engine</span>

A U engine is a piston engine made up of two separate straight engines placed side-by-side and coupled to a shared output shaft. When viewed from the front, the engine block resembles the letter "U".

<span class="mw-page-title-main">Flat-six engine</span> Horizontally opposed 6-cylinder piston 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 cylinders moves inwards and outwards at the same time. An alternative configuration for flat engines is a 180-degree V engine, where both cylinders move to the right then the left at the same time.

<span class="mw-page-title-main">Balance shaft</span> Weights used to balance otherwise unbalanced engine movement

Balance shafts are used in piston engines to reduce vibration by cancelling out unbalanced dynamic forces. The counter balance shafts have eccentric weights and rotate in opposite direction to each other, which generates a net vertical force.

<span class="mw-page-title-main">Motorcycle engine</span> Engine that powers a motorcycle

A motorcycle engine is an engine that powers a motorcycle. Motorcycle engines are typically two-stroke or four-stroke internal combustion engines, but other engine types, such as Wankels and electric motors, have been used.

<span class="mw-page-title-main">Crossplane</span> Crankshaft with throws extending in two planes

The crossplane or cross-plane is a crankshaft design for piston engines with a 90° angle between the crank throws. The crossplane crankshaft is the most popular configuration used in V8 road cars.

<span class="mw-page-title-main">Stroke ratio</span> Mechanical measurement

Stroke ratio, today universally defined as bore/stroke ratio, is a term to describe the ratio between cylinder bore diameter and piston stroke length in a reciprocating piston engine. This can be used for either an internal combustion engine, where the fuel is burned within the cylinders of the engine, or external combustion engine, such as a steam engine, where the combustion of the fuel takes place outside the working cylinders of the engine.

A flat-eight engine, also called a horizontally-opposed eight, is an eight-cylinder piston engine with two banks of four inline cylinders, one on each side of a central crankshaft, 180° apart.

<span class="mw-page-title-main">Single-cylinder engine</span> Piston engine with one cylinder

A single-cylinder engine, sometimes called a thumper, is a piston engine with one cylinder. This engine is often used for motorcycles, motor scooters, motorized bicycles, go-karts, all-terrain vehicles, radio-controlled vehicles, power tools and garden machinery. Single-cylinder engines are made both as 4-strokes and 2-strokes.

<span class="mw-page-title-main">V8 engine</span> Piston engine with eight cylinders in V-configuration

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.

References

  1. 1 2 3 4 Nunney, M J (2006). Light and Heavy Vehicle Technology (4th ed.). Butterworth-Heinemann. ISBN   0-7506-8037-7.
  2. ↑ "Performance: The new 718 Boxster". Porsche. 2016. Retrieved 2016-11-01.
  3. ↑ Schembari, James (2010-10-15). "A Family Sedan Firing on Fewer Cylinders - 2010 Buick LaCrosse CX - Review". The New York Times.
  4. ↑ Ulrich, Lawrence (2010-08-13). "Four-Cylinder Engines Are Smaller, Quieter and Gaining New Respect". The New York Times.
  5. ↑ "Explore the Automotive Trends Data". November 2021. Retrieved 2021-11-25.
  6. ↑ "4-Zylinder Reihenmotor für Nutzfahrzeuge" (PDF). Archived from the original (PDF) on 2011-07-14. Retrieved 2011-08-01.
  7. ↑ "MAN Truck & Bus - TGL". Archived from the original on 2011-05-23. Retrieved 2011-05-09.
  8. ↑ "VARIOmobil - Welcome to a lap of luxury coaches - recreation vehicles - motor homes". Archived from the original on 2011-08-27. Retrieved 2011-05-09.
  9. ↑ "Isuzu Commercial Vehicles - Low Cab Forward Trucks - Commercial Vehicles - 4HK1-TC 5.2L Diesel Engine". Archived from the original on 2010-12-24. Retrieved 2010-12-14.
  10. ↑ "Euro 4 'Forward' F11O.21O" (PDF). Archived from the original (PDF) on 2010-11-26. Retrieved 2010-12-14.
  11. ↑ "Diesel Engines | Products". Hino Global. Retrieved 2017-05-23.
  12. ↑ "Hino 500 Series" (PDF). Archived from the original (PDF) on 2010-12-14. Retrieved 2010-12-14.
  13. ↑ Carney, Dan (2014-06-10). "Before they were carmakers". UK: BBC. Retrieved 2018-11-01.
  14. ↑ Nadel, Brian (June 1989). "Balancing Act". Popular Science. p. 52.
  15. ↑ Pajero/Montero Specifications (PDF)
  16. ↑ "MITSUBISHI MOTORS in Deutschland". Mitsubishi-motors.de. 2016-08-16. Archived from the original on 2013-06-06. Retrieved 2017-05-23.
  17. ↑ "GIUSEPPE BUSSO, 1913-2006: A TRIBUTE TO ALFA ROMEO AND FERRARI'S GREAT ENGINEER". www.italiaspeed.com.
  18. ↑ "Variable Valve Timing (VVT)". www.autobytel.com.
  19. 1 2 3 4 Ludvigsen, Karl (2001). Classic Racing Engines. Haynes Publishing. ISBN   1-85960-649-0.
  20. ↑ "BMW Turbo F1 Engine". Gurneyflap.com. Retrieved 2010-09-13.
  21. ↑ Siegal, Margie (May–June 2017). "The Same, But Different: 1927 Cleveland 4-45 and 4-61 Motorcycles". Motorcycle Classics . Retrieved 2017-06-20.
  22. ↑ Edwards, David (August 1997). Edwards, David (ed.). "Four-Runners". Cycle World . 36 (8). Newport Beach, CA USA: Hachette Filipacchi Magazines: 42–43. ISSN   0011-4286 . Retrieved 2013-09-21.
  23. ↑ Hamish, Cooper (January–February 2018). "Radical Rondine: 1939 Gilera 500 Rondine". Motorcycle Classics . Retrieved 2018-04-13.
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