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A straight-three engine, also known as an inline-triple, or inline-three (abbreviated I3, L3 or R3), is a reciprocating piston internal combustion engine with three cylinders arranged in a straight line or plane, side by side.
Straight-three engines employ a crank angle of either 120° or 180°.
120° cranks are rotationally balanced; however, since the three cylinders are offset from each other, the firing of the end cylinders induces a rocking motion from end to end, since there is no opposing cylinder moving in the opposite direction as in a rotationally balanced straight-six engine. The use of a balance shaft in an antiphase to that vibration produces a smoothly running engine.
A 180° crankshaft can be found in straight-three engines made by motorcycle manufacturer Laverda and in small cars such as the Suzuki Cultus 1.0. In these engines, the outer pistons rise and fall together like a 360° straight-two engine. The inner cylinder is offset 180° from the outer cylinders. In these engines, cylinder number one fires, then 180° later cylinder number two fires, and then 180° later cylinder number three fires. There is no power stroke on the final 180° of rotation.
The smallest inline-three, four-stroke automobile engine was the 543 cubic centimetres (33.1 cu in) Suzuki F5A, which was first used in the 1979 Suzuki Alto/Fronte. Smart currently produces a diminutive 799 cubic centimetres (48.8 cu in) inline-three diesel engine, the smallest automotive diesel engine yet. Most inline-three engines fall below 1.2 litres, with a 1,198 cubic centimetres (73.1 cu in) Volkswagen Group unit seen as the largest petrol engine. A 1,779 cubic centimetres (108.6 cu in) diesel engine was produced by VM Motori to the 1984 Alfa Romeo 33 1.8 TD, the largest inline-three produced for automotive use.
Basic versions of the Suzuki Swift/Forsa and related Chevy Sprint/Geo Metro/Chevy Metro/Pontiac Firefly used an inline-three.
Some Daihatsu cars use straight-three engines. The Charade used and the Mira/Cuore uses this engine type. Three-cylinder 1.0 litre diesel and turbo diesel engines were also offered in Daihatsu Charades. Korean cars Daewoo Tico, based on the 1988 Suzuki Alto, and later base versions of Daewoo Matiz also used inline-three 796 cubic centimetres (48.6 cu in) 41 horsepower (31 kW; 42 PS) S-TEC petrol engine.
The Volkswagen Group is known for using three-cylinder petrol and diesel engines; in the Audi A2, Volkswagen Polo, Volkswagen Fox, SEAT Ibiza and Škoda Fabia. The engines in these cars range from 1.2 litre petrol with four valves per cylinder that deliver 47 to 65 kilowatts (64 to 88 PS; 63 to 87 bhp), to 1.4 TDI diesels that deliver 51 to 66 kilowatts (69 to 90 PS; 68 to 89 bhp) and have turbos with variable vane geometry and deliver outstanding economy, this particular engine is used in small cars of all marques of the Volkswagen Group. The most innovative three-cylinder engine the Volkswagen Group released was the 1.2 TDI diesel, it was one of the first all-aluminium diesel engines, and at the time of release it was the lightest and most economic engine in production. It was used in the "3L" versions (from its diminutive fuel consumption of only 3 litres per 100 kilometres or 94.2 miles per imperial gallon; 78.4 miles per US gallon) of the Audi A2 and the Volkswagen Lupo.
In the 1950s and 1960s, the Saab 93, Saab 95, Saab 96, and certain DKW automobiles were powered by inline-three-cylinder, two-stroke engines. Also, the Wartburg automobiles manufactured in Eastern Germany, and FSO Syrena manufactured in Poland, used this kind of engine.
Ford started offering their new 1.0 Ecoboost unit in the Focus from 2012. This new engine features several innovations, including the use of an unbalanced flywheel to remove the need to use balancer shafts.
The Triumph Rocket III, has a 2,294 cc (140.0 cu in) straight-three engine and the company has produced a number of other transversely mounted straight-three engines, such as the water-cooled Daytona 955i, which was also the company's first fuel injected machine; and 1,050 cc Speed Triple.
Following a comparative study at Osaka University's Faculty of Engineering, between in-line and L-shaped motors, Kawasaki Motors decided to develop a range of high performance, two stroke straight-three engines. Between 1969 and 1978, the company produced air-cooled inline, triple engines with capacities of 250 cc, 350 cc, 400 cc, 500 cc, and 750 cc, and the H1-R 500cc and H2-R or KR750 750 cc racing models in both air-cooled and water-cooled forms.
Inline three-cylinder engines are not limited to propelling motor vehicles. The may also be used in general industrial applications. An example is the Fairbanks-Morse 32E14 slow-speed diesel engine which is shown coupled to a water pump.
Inline 3 engines are very common in diesel engined tractors, as well as other agricultural machinery. Nearly all manufacturers of diesel tractors have or have had models with 3 cylinder engines on their program. The perhaps best known example of any kind of 3 cylinder diesel engine is the Perkins AD3.152 that were used in Massey Ferguson 35 tractors, as well as in Fordson Dexta and several other tractors. This engine was also used for marine and stationary applications. Other examples of manufacturers include Nuffield(BMC), Bolinder-Munktell/Volvo BM, International Harvester, John Deere, Deutz-Fahr, Ford and many others.
- Robson, Graham (August 15, 2010). "The car and the team". Saab 96 & V4. Rally Giants. Veloce Publishing. p. 27. ISBN 978-1-84584-256-7. "V4 replaces straight three"
- Let's Ride: Sonny Barger's Guide to Motorcycling. Sonny Barger, Darwin Holmstrom. HarperCollins, 8 Jun 2010
- Superbikes: The World's Top Performance Machines. Alan Dowds. Tangerine Press, 2004
- Cycle world, Volume 44. CBS Publications, 2005
- Gorant, Jim (December 1997). "Jet Ski Saviors". In Oldham, Joe. Popular Mechanics (New York, NY USA: Hearst) 174 (12): 54–57. ISSN 0032-4558. Retrieved 2012-07-02. "The 1071cc, inline, triple-cylinder configuration produces 803 pounds of thrust and pushes the boat to about 55 mph."
- Dinkel, John, ed. (July 1988). "Comparison Road Test: 3x3". Road & Track (Newport Beach, CA USA: Diamandis Communications) 39 (11): 66–74. ISSN 0035-7189. "Its engine is still the same 993-cc sohc inline-3, producing 48 bhp at 5100 5100 rpm and 57 lb-ft torque at 3200..."
- Mayersohn, Norman; Zino, Ken (March 1988). "Car of the Future Part 3 of a Series – Power for Tomorrow". In Oldham, Joe. Popular Mechanics (New York, NY USA: Hearst) 165 (3): 53–57. ISSN 0032-4558. Retrieved 2012-07-02. "Under a more sophisticated modular engine plan, a basic 3-liter V6 could be split into an inline Three, chopped into a V4 or melded into a V12."
- "Inline 3-cylinder engines". Mark Wan - AutoZine Technical School. AutoZine.org. Retrieved 3 January 2010.
- Logan (September 23, 2011). "New car: 2012 Daihatsu Mira e:S". Motor Mania. Retrieved 2012-07-03. "Motivation comes from a 3-cylinder, 650cc petrol engine that kicks out a mere 51bhp (52PS/38kW) and 60Nm (44lb-ft) of torque."
- "New VW Fox in depth". Volkswagen AG. WorldCarFans.com. 2005-04-04. Retrieved 2009-08-18.
- "New Audi A2 1.4 TDI with 90 bhp engine". AUDI AG. WorldCarFans.com. 2003-11-10. Retrieved 2009-08-22.
- "Audi A2 1.2 TDI: the three-litre car from Audi". AUDI AG - press release. AudiWorld.com. 1999-11-28. Retrieved 2009-08-22.
- Jackson, Paul (February 1, 2008). "Chapter 6: The Next Generation". The Little Book of Smart. Veloce Publishing. pp. 94–95. ISBN 978-1-84584-148-5. "There were plenty of changes under the skin, too, with the original smart-built turbocharged engine being replaced (on petrol-engined versions) by a Mitsubishi design – still with three cylinders but now a larger (999cc) capacity."
- How Your Motorcycle Works: Your Guide to the Components & Systems of Modern Motorcycles. Peter Henshaw Veloce Publishing Ltd, 15 Sep 2012
- 365 Motorcycles You Must Ride. Dain Gingerelli, Charles Everitt, James Manning Michels. MBI Publishing Company, 10 Jan 2011
- The Motorcycle Book, Alan Seeley. MotorBooks International, 2 May 2004
- Human Hurricane, Wilson, Steve. Walneck's Classic Cycle Trader, April 2005
- Triumph Motorcycles: Twins & Triples. Timothy Remus. MotorBooks International, 10 Oct 1997
- The Illustrated Directory of Motorcycles. Micro De Cet, Mirco De Cet. MotorBooks International, 13 Feb 2003
- Superbikes: The World's Top Performance Machines. Alan Dowds 0 Reviews Tangerine Press, 2004
- Cycle world, Volume 44 CBS Publications, 2005. "inline triple"
- Japanese Production Racing Motorcycles. Mick Walker. Redline Books, Sep 2004
- The Kawasaki Triples Bible: All Road Models 1968-1980, Plus H1r and H2r Racers in Profile. Alastair Walker, Veloce Publishing Ltd, 15 Jan 2011. P.18
- 365 Motorcycles You Must Ride. Dain Gingerelli, Charles Everitt, James Manning Michels. MBI Publishing Company, 10 Jan 2011. P.188
- “Pilot” magazine February 1986 page 32
- Media related to Straight-3 engines at Wikimedia Commons