Straight-four 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.
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
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
However, straight-four engines have a
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
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
Usage in production cars
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:
- 1954–1994 Alfa Romeo Twin Cam engine: one of the first mass-produced twin-cam engines.[17] In 1990, it became the first production engine with variable valve timing.[18]
- 1908–1941 Ford Model T engine: one of the most widely produced engines in the world.
- 1951–2000 BMC A-Series engine: the first engine to be used in a mass-production transverse-engined front-wheel drive car.
- 1966–2000 Fiat Twin Cam engine: one of the first mass-produced twin-cam engines, produced from 1959.
- 1968–1981 Triumph Slant-4 engine: an early multi-valveengine which formed the basis of Saab's first turbocharged engines.
- 2000–2009 Honda F20C engine: produced the highest specific output for a naturally aspirated engine of its time.
Usage in racing cars
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
Many cars produced for the pre-WWII
Another engine that played an important role in racing history is the straight-four
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
Belgian arms manufacturer
The first across-the-frame 4-cylinder motorcycle was the 1939 racer
The 2009
Inline-four engines are also used in
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
References
- ^ ISBN 0-7506-8037-7.
- ^ "Performance: The new 718 Boxster". Porsche. 2016. Retrieved 2016-11-01.
- ^ Schembari, James (2010-10-15). "A Family Sedan Firing on Fewer Cylinders - 2010 Buick LaCrosse CX - Review". The New York Times.
- ^ Ulrich, Lawrence (2010-08-13). "Four-Cylinder Engines Are Smaller, Quieter and Gaining New Respect". The New York Times.
- ^ "Explore the Automotive Trends Data". November 2021. Retrieved 2021-11-25.
- ^ "4-Zylinder Reihenmotor für Nutzfahrzeuge" (PDF). Archived from the original (PDF) on 2011-07-14. Retrieved 2011-08-01.
- ^ "MAN Truck & Bus - TGL". Archived from the original on 2011-05-23. Retrieved 2011-05-09.
- ^ "VARIOmobil - Welcome to a lap of luxury coaches - recreation vehicles - motor homes". Archived from the original on 2011-08-27. Retrieved 2011-05-09.
- ^ "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.
- ^ "Euro 4 'Forward' F11O.21O" (PDF). Archived from the original (PDF) on 2010-11-26. Retrieved 2010-12-14.
- ^ "Diesel Engines | Products". Hino Global. Retrieved 2017-05-23.
- ^ "Hino 500 Series" (PDF). Archived from the original (PDF) on 2010-12-14. Retrieved 2010-12-14.
- ^ Carney, Dan (2014-06-10). "Before they were carmakers". UK: BBC. Retrieved 2018-11-01.
- ^ Nadel, Brian (June 1989). "Balancing Act". Popular Science. p. 52.
- ^ Pajero/Montero Specifications (PDF)
- ^ "MITSUBISHI MOTORS in Deutschland". Mitsubishi-motors.de. 2016-08-16. Archived from the original on 2013-06-06. Retrieved 2017-05-23.
- ^ "GIUSEPPE BUSSO, 1913-2006: A TRIBUTE TO ALFA ROMEO AND FERRARI'S GREAT ENGINEER". www.italiaspeed.com.
- ^ "Variable Valve Timing (VVT)". www.autobytel.com.
- ^ ISBN 1-85960-649-0.
- ^ "BMW Turbo F1 Engine". Gurneyflap.com. Retrieved 2010-09-13.
- ^ Siegal, Margie (May–June 2017). "The Same, But Different: 1927 Cleveland 4-45 and 4-61 Motorcycles". Motorcycle Classics. Retrieved 2017-06-20.
- ISSN 0011-4286. Retrieved 2013-09-21.
- ^ Hamish, Cooper (January–February 2018). "Radical Rondine: 1939 Gilera 500 Rondine". Motorcycle Classics. Retrieved 2018-04-13.
External links
- Media related to Straight-4 engines at Wikimedia Commons