fbpx
Wikipedia

Flat-four engine

May 14, 2023

A flat-four engine, also known as a horizontally opposed-four 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.

2007 ULPower UL260i aircraft engine

A boxer-four engine has perfect primary and secondary balance, however, the two cylinder heads means the design is more expensive to produce than an inline-four engine. There is a minor, secondary unbalanced rotational torque pulse in the plane of the pistons, when a piston pair at one end of the engine is at TDC and the other pair at BDC. The TDC pair creates a torque greater than the BDC pair, so the net unbalanced torque pulse is the difference. The difference in TDC vs BDC inertial forces is explained in the Engine balance section. Boxer-four engines have been used in cars since 1897, especially by Volkswagen and Subaru. They have also occasionally been used in motorcycles and frequently in aircraft. Cessna and Piper use flat four engines from Lycoming and Continental in the most common civil aircraft in the world - the Cessna 172, and Piper Cherokee, while many ultralight and LSA planes use versions of the Rotax 912.

Design

 
Boxer-four animation

Most flat-four engines are designed so that each pair of opposing pistons moves inwards and outwards at the same time, which is known as a "boxer" configuration (somewhat like boxing competitors punching their gloves together before a fight). Therefore, the terms "flat-four" and "boxer-four" are often used synonymously.

The advantages of the boxer-four layout are perfect secondary vibration (resulting in minimal vibration), a low centre of gravity, and a short engine length. The layout also lends itself to efficient air cooling with the airflow being evenly distributed across the four cylinders. In aircraft, this avoids the need to carry heavy water cooling systems.

The downsides of boxer-four engines (compared with inline-four engines) are their extra width, the increased costs associated with having two cylinder heads instead of one, and the long exhaust manifold required to achieve evenly spaced exhaust pulses.[1] Due to these factors, inline-four engines are more commonly used than flat-four engines, and V6 engines are often used where larger displacements are required.

Engine balance

The equal and opposing forces generated in a boxer-four engine result in perfect secondary balance (unlike the unbalanced vertical forces produced by inline-four engines). Boxer-four engines are therefore better suited to displacements above 2.0 L (122 cu in), since they do not require balance shafts to reduce the secondary vibration.

In practice, each cylinder in a boxer engine is slightly offset from its opposing pair due to the distance between the crankpins along the crankshaft. This offset distance means that the equal and opposite forces from each cylinder pair produces a rocking couple.[2]: 27  The resulting vibration is not usually high enough to require balance shafts.

As per all four-stroke engines with four cylinder or less, the lack of overlap in the power strokes results in a pulsating delivery of torque to the flywheel, causing a torsional vibration along the crankshaft axis.[3] If necessary, this vibration can be minimised using a harmonic damper.

Exhaust manifold

The typical firing order for a boxer-four engine is for the left bank of cylinders to ignite one after another, followed by the right bank of cylinders (or vice versa), with the firing interval evenly spaced at 180 degrees. Traditionally, the exhausts from the two cylinders on each bank were merged, with the resulting uneven exhaust pulses causing a characteristic "flat-four burble" exhaust sound.

The other common exhaust configuration (such as used by Subaru since the mid-2000s) is to pair the cylinders with a firing interval offset of 360 degrees, in order to optimise the exhaust pulses.[4][5][6] This configuration requires long exhaust manifolds, in order to pair the cylinders on opposite banks, and results in a less distinctive exhaust sound.

Use in automobiles

1900–1935

 
1904 Wilson-Pilcher water-cooled engine

In 1900, the first flat-four engine was produced by Benz & Cie, based on Benz's 1897 "contra" flat-twin engine.[citation needed] This engine was used in Benz racing cars, produced 20 hp (15 kW), had a displacement of 5.4 L (330 cu in) and was designed by Georg Diehl.

London company Wilson-Pilcher released its first car in 1901, which was powered by a flat-four engine. This engine was mounted longitudinally in the chassis, water-cooled, produced 9 hp (7 kW) and had a displacement of 2.4 L (146 cu in). Unusually for its day, the bore and stroke were equal, with each being 95 mm (3.7 in).

In 1902 the Buffum automobile was equipped with opposed four cylinder engines that were rated at 16 horsepower. Herbert H. Buffum produced an American Automobile called the Buffum in Abington, Massachusetts from 1903 to 1907.[7]

Having previously produced flat-twin engines, the 1926 Tatra 30 was the Czech company's first model powered by a flat-four engine. Tatra produced various flat-four engined model through the 1920s and 1930s.

1936–1999

 
1952 Jowett Jupiter water-cooled engine
 
1955 Porsche 550 Spyder air-cooled engine

The 1936 Tatra T97 pioneered the rear-engined, air-cooled flat-four, backbone chassis layout (later used by the Volkswagen Beetle), and at the same time, though unrelated, came the Steyr 50 from Austria, sporting a front boxer 4 engine with rear wheel drive. Also in 1936, English company Jowett expanded its model range from flat-twin engines to also include flat-four engines. Production of Jowett flat-four engines continued until 1954, when the Jowett Javelin saloon and Jowett Jupiter sports models ended production.

The longest production flat-four engine is the Volkswagen air-cooled engine, which was produced from 1938 until 2006 and was most famously used in the rear-engined 1938–2003 Volkswagen Beetle and 1950–2005 Volkswagen Transporter.[8] This air-cooled engine was designed by Porsche and was also used in the 1948–1965 Porsche 356, 1953–1956 Porsche 550, 1965–1969 Porsche 912 and 1969–1976 Porsche 914. In 1982, to comply with exhaust emissions regulations a water-cooled version called the Volkswagen Wasserboxer was introduced in the Volkswagen Transporter (T3)

During the 1960s and 1970s, several manufacturers produced flat-four engines including the air-cooled Citroën flat-four engine, the water-cooled Alfa Romeo flat-four engine, the water-cooled Lancia flat-four engine and the water-cooled Subaru EA engine.

Two important engines designed during this period, but never saw the light of day in series production, were the Morris 800cc side valve engine by Alec Issigonis in 1947 originally destined for the Morris Minor, and the Ferguson 2.2 litre SOHC engine by Claude Hill in 1966 as part of the R5 vehicle research project.

2000–present

 
2012–present Subaru FA water-cooled engine

By 2000, most manufacturers had replaced flat-four engines with inline-four engines. A notable exception is Subaru, with the water-cooled Subaru EJ engine being available in turbocharged form in the Subaru WRX sports sedan and its World Rally Car counterpart. Subaru's adoption of all-wheel drive was a factor in retaining the flat-four engine, since the shorter length of this engine assists in fitting the all-wheel drive components into the chassis.[9] Although it is more expensive than an inline-four engine, the flat-four engine allows Subaru to build an all-wheel drive vehicle at little extra cost from two-wheel drive.[9]

In 2012, a naturally aspirated version of the Subaru FA engine was used in the Toyota 86 (also called the "Subaru BRZ" and "Scion FR-S") rear-wheel drive sports coupe.[10] This engine is water-cooled, has gasoline direct injection, produces 147 kW (197 hp) and has a displacement of 2.0 L (122 cu in).

The 2016 Porsche Boxster/Cayman (982) mid-engined sports cars downsized from a naturally aspirated flat-six engine to a turbocharged flat-four engine, Porsche's first flat-four since the mid-1970s. This engine is produced in displacements of 2.0–2.5 L (122–153 cu in) and produces up to 365 hp (272 kW).[11] Several reviewers criticised the Boxster/Cayman for an uninspiring engine sound.[12][13][14]

Use in motorcycles

See also: Motorcycle engine

Most motorcycles with four-cylinder engines use an inline-four engine layout, however, several flat-four engine engines have been used in shaft drive motorcycles:

Use in aircraft

 
ULPower UL260i aircraft engine

Light aircraft commonly use flat-four engines with displacements up to 6.4 L (390 cu in) from manufacturers such as Lycoming Engines, Continental Motors and Franklin Engine Company.

For radio-controlled aircraft, flat-four engines with displacements of 40–50 cc (2.4–3.1 cu in) are produced by companies such as O.S. Engines.

See also

References

  1. ^ Nunney, M. J. (2007). Light and Heavy Vehicle Technology. Butterworth-Heinemann. p. 13. ISBN 978-0-7506-8037-0.
  2. ^ Wilson, Hugo (1995). "The A–Z of Motorcycles". The Encyclopedia of the Motorcycle. London, UK: Dorling Kindersley. ISBN 0-7513-0206-6.
  3. ^ Thomson. Vibration Theory and Applications. p. 190. Dynamics of reciprocating forces. Prentice Hall Inc., USA, 1965.
  4. ^ Announcement on Legacy exhaust in Japanese: . 2003-05-23. Archived from the original on 2016-05-15. Retrieved 2013-12-16.
  5. ^ Announcement on Forester exhaust in Japanese: "Fuji Heavy Industries, News Release". 2005-01-27. Retrieved 2013-12-16.
  6. ^ Announcement on Impreza exhaust in Japanese: "Fuji Heavy Industries, News Release". 2007-06-05. Retrieved 2013-12-16.
  7. ^ "The Buffum Automobile". Farber and Associates.
  8. ^ "The engine that Benz built still survives". www.theglobeandmail.com. Retrieved 1 September 2019.
  9. ^ a b Stepler, Richard (September 1994). "Preview Drive: Three Ways to Get a Grip". Popular Science. 245 (3): 44. Retrieved 2011-10-23.
  10. ^ Bonk, Aaron (2013-02-07) (2013-02-07). . Archived from the original on 2014-02-27. Retrieved 8 January 2014.
  11. ^ "Performance: The new 718 Boxster". Porsche. 2016. Retrieved 2016-11-01.
  12. ^ "2019 Porsche 718 Cayman". www.caranddriver.com. 14 May 2019. Retrieved 1 September 2019.
  13. ^ "Porsche 718 Cayman review – The entry-level Porsche punches above its weight". www.evo.co.uk. Retrieved 1 September 2019.
  14. ^ "2017 Porsche 718 Cayman First Drive Review: Performance Trumps Sound". www.motortrend.com. Retrieved 1 September 2019.
  15. ^ Julian Marsh (2000-06-10). "BFG and MF motorcycles". Citroenet.org.uk. Retrieved 2011-12-06.
  16. ^ Julian Marsh. "GS & GSA boxer engine". Citroenet.org.uk. Retrieved 2011-12-06.
 
Wikimedia Commons has media related to Flat-4 engines.

May 14, 2023
flat, four, engine, flat, four, engine, also, known, horizontally, opposed, four, engine, four, cylinder, piston, engine, with, banks, cylinders, lying, opposite, sides, common, crankshaft, most, common, type, flat, four, engine, boxer, four, engine, each, pai. A flat four engine also known as a horizontally opposed four 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 2007 ULPower UL260i aircraft engine A boxer four engine has perfect primary and secondary balance however the two cylinder heads means the design is more expensive to produce than an inline four engine There is a minor secondary unbalanced rotational torque pulse in the plane of the pistons when a piston pair at one end of the engine is at TDC and the other pair at BDC The TDC pair creates a torque greater than the BDC pair so the net unbalanced torque pulse is the difference The difference in TDC vs BDC inertial forces is explained in the Engine balance section Boxer four engines have been used in cars since 1897 especially by Volkswagen and Subaru They have also occasionally been used in motorcycles and frequently in aircraft Cessna and Piper use flat four engines from Lycoming and Continental in the most common civil aircraft in the world the Cessna 172 and Piper Cherokee while many ultralight and LSA planes use versions of the Rotax 912 Contents 1 Design 1 1 Engine balance 1 2 Exhaust manifold 2 Use in automobiles 2 1 1900 1935 2 2 1936 1999 2 3 2000 present 3 Use in motorcycles 4 Use in aircraft 5 See also 6 ReferencesDesign Edit Boxer four animation Most flat four engines are designed so that each pair of opposing pistons moves inwards and outwards at the same time which is known as a boxer configuration somewhat like boxing competitors punching their gloves together before a fight Therefore the terms flat four and boxer four are often used synonymously The advantages of the boxer four layout are perfect secondary vibration resulting in minimal vibration a low centre of gravity and a short engine length The layout also lends itself to efficient air cooling with the airflow being evenly distributed across the four cylinders In aircraft this avoids the need to carry heavy water cooling systems The downsides of boxer four engines compared with inline four engines are their extra width the increased costs associated with having two cylinder heads instead of one and the long exhaust manifold required to achieve evenly spaced exhaust pulses 1 Due to these factors inline four engines are more commonly used than flat four engines and V6 engines are often used where larger displacements are required Engine balance Edit The equal and opposing forces generated in a boxer four engine result in perfect secondary balance unlike the unbalanced vertical forces produced by inline four engines Boxer four engines are therefore better suited to displacements above 2 0 L 122 cu in since they do not require balance shafts to reduce the secondary vibration In practice each cylinder in a boxer engine is slightly offset from its opposing pair due to the distance between the crankpins along the crankshaft This offset distance means that the equal and opposite forces from each cylinder pair produces a rocking couple 2 27 The resulting vibration is not usually high enough to require balance shafts As per all four stroke engines with four cylinder or less the lack of overlap in the power strokes results in a pulsating delivery of torque to the flywheel causing a torsional vibration along the crankshaft axis 3 If necessary this vibration can be minimised using a harmonic damper Exhaust manifold Edit The typical firing order for a boxer four engine is for the left bank of cylinders to ignite one after another followed by the right bank of cylinders or vice versa with the firing interval evenly spaced at 180 degrees Traditionally the exhausts from the two cylinders on each bank were merged with the resulting uneven exhaust pulses causing a characteristic flat four burble exhaust sound The other common exhaust configuration such as used by Subaru since the mid 2000s is to pair the cylinders with a firing interval offset of 360 degrees in order to optimise the exhaust pulses 4 5 6 This configuration requires long exhaust manifolds in order to pair the cylinders on opposite banks and results in a less distinctive exhaust sound Use in automobiles Edit1900 1935 Edit 1904 Wilson Pilcher water cooled engine In 1900 the first flat four engine was produced by Benz amp Cie based on Benz s 1897 contra flat twin engine citation needed This engine was used in Benz racing cars produced 20 hp 15 kW had a displacement of 5 4 L 330 cu in and was designed by Georg Diehl London company Wilson Pilcher released its first car in 1901 which was powered by a flat four engine This engine was mounted longitudinally in the chassis water cooled produced 9 hp 7 kW and had a displacement of 2 4 L 146 cu in Unusually for its day the bore and stroke were equal with each being 95 mm 3 7 in In 1902 the Buffum automobile was equipped with opposed four cylinder engines that were rated at 16 horsepower Herbert H Buffum produced an American Automobile called the Buffum in Abington Massachusetts from 1903 to 1907 7 Having previously produced flat twin engines the 1926 Tatra 30 was the Czech company s first model powered by a flat four engine Tatra produced various flat four engined model through the 1920s and 1930s 1936 1999 Edit 1952 Jowett Jupiter water cooled engine 1955 Porsche 550 Spyder air cooled engine The 1936 Tatra T97 pioneered the rear engined air cooled flat four backbone chassis layout later used by the Volkswagen Beetle and at the same time though unrelated came the Steyr 50 from Austria sporting a front boxer 4 engine with rear wheel drive Also in 1936 English company Jowett expanded its model range from flat twin engines to also include flat four engines Production of Jowett flat four engines continued until 1954 when the Jowett Javelin saloon and Jowett Jupiter sports models ended production The longest production flat four engine is the Volkswagen air cooled engine which was produced from 1938 until 2006 and was most famously used in the rear engined 1938 2003 Volkswagen Beetle and 1950 2005 Volkswagen Transporter 8 This air cooled engine was designed by Porsche and was also used in the 1948 1965 Porsche 356 1953 1956 Porsche 550 1965 1969 Porsche 912 and 1969 1976 Porsche 914 In 1982 to comply with exhaust emissions regulations a water cooled version called the Volkswagen Wasserboxer was introduced in the Volkswagen Transporter T3 During the 1960s and 1970s several manufacturers produced flat four engines including the air cooled Citroen flat four engine the water cooled Alfa Romeo flat four engine the water cooled Lancia flat four engine and the water cooled Subaru EA engine Two important engines designed during this period but never saw the light of day in series production were the Morris 800cc side valve engine by Alec Issigonis in 1947 originally destined for the Morris Minor and the Ferguson 2 2 litre SOHC engine by Claude Hill in 1966 as part of the R5 vehicle research project 2000 present Edit 2012 present Subaru FA water cooled engine By 2000 most manufacturers had replaced flat four engines with inline four engines A notable exception is Subaru with the water cooled Subaru EJ engine being available in turbocharged form in the Subaru WRX sports sedan and its World Rally Car counterpart Subaru s adoption of all wheel drive was a factor in retaining the flat four engine since the shorter length of this engine assists in fitting the all wheel drive components into the chassis 9 Although it is more expensive than an inline four engine the flat four engine allows Subaru to build an all wheel drive vehicle at little extra cost from two wheel drive 9 In 2012 a naturally aspirated version of the Subaru FA engine was used in the Toyota 86 also called the Subaru BRZ and Scion FR S rear wheel drive sports coupe 10 This engine is water cooled has gasoline direct injection produces 147 kW 197 hp and has a displacement of 2 0 L 122 cu in The 2016 Porsche Boxster Cayman 982 mid engined sports cars downsized from a naturally aspirated flat six engine to a turbocharged flat four engine Porsche s first flat four since the mid 1970s This engine is produced in displacements of 2 0 2 5 L 122 153 cu in and produces up to 365 hp 272 kW 11 Several reviewers criticised the Boxster Cayman for an uninspiring engine sound 12 13 14 Use in motorcycles EditSee also Motorcycle engine Honda GL1000 Most motorcycles with four cylinder engines use an inline four engine layout however several flat four engine engines have been used in shaft drive motorcycles 1938 1939 Zundapp K800 air cooled 1974 1987 Honda Gold Wing liquid cooled 1955 1956 Wooler 500cc air cooled 1981 1982 BFG 1300 in French using the air cooled Citroen flat four car engine Approximately 450 were built with one quarter of these purchased by the French police 15 16 Use in aircraft Edit ULPower UL260i aircraft engine Light aircraft commonly use flat four engines with displacements up to 6 4 L 390 cu in from manufacturers such as Lycoming Engines Continental Motors and Franklin Engine Company For radio controlled aircraft flat four engines with displacements of 40 50 cc 2 4 3 1 cu in are produced by companies such as O S Engines See also EditInline four engine V4 engineReferences Edit Nunney M J 2007 Light and Heavy Vehicle Technology Butterworth Heinemann p 13 ISBN 978 0 7506 8037 0 Wilson Hugo 1995 The A Z of Motorcycles The Encyclopedia of the Motorcycle London UK Dorling Kindersley ISBN 0 7513 0206 6 Thomson Vibration Theory and Applications p 190 Dynamics of reciprocating forces Prentice Hall Inc USA 1965 Announcement on Legacy exhaust in Japanese Fuji Heavy Industries Press Information 2003 05 23 Archived from the original on 2016 05 15 Retrieved 2013 12 16 Announcement on Forester exhaust in Japanese Fuji Heavy Industries News Release 2005 01 27 Retrieved 2013 12 16 Announcement on Impreza exhaust in Japanese Fuji Heavy Industries News Release 2007 06 05 Retrieved 2013 12 16 The Buffum Automobile Farber and Associates The engine that Benz built still survives www theglobeandmail com Retrieved 1 September 2019 a b Stepler Richard September 1994 Preview Drive Three Ways to Get a Grip Popular Science 245 3 44 Retrieved 2011 10 23 Bonk Aaron 2013 02 07 2013 02 07 How Boxer Engines Work And Why You Should Care About Subaru s New FA20 Archived from the original on 2014 02 27 Retrieved 8 January 2014 Performance The new 718 Boxster Porsche 2016 Retrieved 2016 11 01 2019 Porsche 718 Cayman www caranddriver com 14 May 2019 Retrieved 1 September 2019 Porsche 718 Cayman review The entry level Porsche punches above its weight www evo co uk Retrieved 1 September 2019 2017 Porsche 718 Cayman First Drive Review Performance Trumps Sound www motortrend com Retrieved 1 September 2019 Julian Marsh 2000 06 10 BFG and MF motorcycles Citroenet org uk Retrieved 2011 12 06 Julian Marsh GS amp GSA boxer engine Citroenet org uk Retrieved 2011 12 06 Wikimedia Commons has media related to Flat 4 engines Retrieved from https en wikipedia org w index php title Flat four engine amp oldid 1154594043, wikipedia, wiki, book, books, library,

article

, read, download, free, free download, mp3, video, mp4, 3gp, jpg, jpeg, gif, png, picture, music, song, movie, book, game, games.