A straight-three engine (also called an inline-triple or inline-three)is a three-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.
Less common than straight-four engines, straight-three engines have nonetheless been used in various motorcycles, cars and agricultural machinery.
A crankshaft angle of 120 degrees is typically used by straight-three engines,since this results in an evenly spaced firing interval. Another benefit of this configuration is perfect primary balance and secondary balance, however an end-to-end rocking couple is induced because there is no symmetry in the piston velocities about the middle piston. A balance shaft is sometimes used to reduce the vibrations caused by the rocking couple.
Other crankshaft angles have been used occasionally. The 1976-1981 Laverda Jota motorcycle used a 180 degree crankshaft, where the outer pistons rise and fall together and inner cylinder is offset from them by 180 degrees. This results in three power strokes evenly-spaced at 180 degrees each, and then no power strokes during the final 180 degrees of crankshaft rotation. The 2020 Triumph Tiger 900 motorcycle uses a "T-Plane" crankshaft where the crankshaft throws are at 90 intervals, such that the throws for cylinders 1 and 3 are separated by 180 degrees (therefore the three throws together forming a "T" shape when viewed from the end).
Among the first cars to use a straight-three engine is the 1953-1955 DKW F91, powered by a 900 cc (55 cu in) two-stroke engine. The 1956-1960 Saab 93 saw the introduction of Saab's 750 cc (46 cu in) two-stroke engine, which was also used in the Saab 95, Saab 96 and Saab Sonett until 1968 after which it was replace by the Ford Taunus V4 engine.
The Wartburg cars (manufactured in East Germany) and FSO Syrena (manufactured in Poland) also used straight-three engines.
The 1967 Suzuki Fronte 360 uses a 256 cc (16 cu in) two-stroke engine. In 1980, Suzuki began production of a 543 cc (33 cu in) four-stroke engine, which was introduced in the Alto and Fronte models.
The Subaru EF engine is a 4-stroke petrol engine which was introduced in 1984 and used in the Justyand the Sumo (the export version of the Sambar).
The straight-three versions of the Ford EcoBoost engine - a turbocharged 1.0-litre petrol engine - was introduced in the 2012 Ford Focus.It uses an unbalanced flywheel to shift the inherent three-cylinder imbalance to the horizontal plane where it is more easily managed by engine mounts, and so remove the need to use balance shafts. In 2016, cylinder deactivation was added, claimed to be a world first for three-cylinder engines.
|1977-1993||Daihatsu C-series||Petrol||Used in the Daihatsu Charade and Daihatsu Mira/Cuore|
|1983-2001||Suzuki G10||Petrol||Debuted in the Suzuki Cultus/Swift|
|1986-1995||VM Motori R392||Diesel||Turbocharged, used in the Alfa Romeo 33|
|1987-present||Mitsubishi 3G8||Petrol||Debuted in the Mitsubishi Minica|
|1991-2008||Daewoo S-TEC||Petrol||Used in the Daewoo Tico and Daewoo Matiz|
|1996-2002||GM X10XE||Petrol||Debuted in the Opel Corsa|
|1998-2007||Mercedes-Benz M160||Petrol||Turbocharged, used by Smart|
|1998-2005||Volkswagen R3 PD TDI 3L||Diesel||Turbocharged, used in the Volkswagen Lupo and Audi A2|
|1999-2014||Mercedes-Benz OM660||Diesel||Turbocharged, used by Smart|
|1999-2005||VN Motori R 315||Diesel||Turbocharged, debuted in the Hyundai Accent|
|2000-2006||Honda ECA1||Petrol||Used by the Honda Insight hybrid car|
|2003-present||Mitsubishi 3A9||Petrol||Debuted in the Mitsubishi Mirage|
|2004-2011||Hyundai U engine||Diesel||Turbocharged, debuted in the Kia Picanto|
|2004-present||Volkswagen R3 (EA111)||Petrol||Debuted in the Volkswagen Fox|
|2004-2009||Mercedes-Benz OM639||Diesel||Turbocharged, used by the Smart Forfour and Mitsubishi Colt|
|2004-present||Toyota 1KR-FE||Petrol||Debuted in the Toyota Aygo|
|2010-present||Nissan HR||Petrol||Some versions supercharged, debuted in the Nissan Micra|
|2011-2017||Fiat XSDE||Diesel||Debuted in the India-market Chevrolet Beat|
|2012-present||Ford EcoBoost||Petrol||Some versions turbocharged, debuted in the Ford Focus (3rd generation)|
|2012-present||BMW B37||Diesel||Turbocharged, debuted in the Mini (F56)|
|2012-present||Renault TCe||Petrol||Turbocharged, debuted in the Renault Clio IV|
|2013-present||BMW B38||Petrol||Turbocharged, debuted in the BMW i8|
|2013-present||GM small gasoline engine||Petrol||Turbocharged, debuted in the Opel Adam|
|2014-present||PSA Group PureTech||Petrol||Turbocharged, debuted in the Peugeot 308|
|2020-present||Toyota G16E||Petrol||Turbocharged, debuted in the Toyota GR Yaris.|
The advantages of a straight-three engine for motorcycles are that it has a shorter length than an inline-four engine and produces less vibration than a straight-twin engine. [ page needed ]
Four-stroke straight-three engines have been used in road bikes and racing bikes by several companies. [ page needed ] [ page needed ] [ page needed ]
From 1985-1995, the BMW K75 was produced with a straight-three engine (based on the straight-four engine from the BMW K100). The British company Triumph has produced several models with transversely-mounted straight-three engines, such as the 1994-present Triumph Speed Tripleand the 2004-present Triumph Rocket III.
In 2019, the Moto2 class in the MotoGP World Championship switched to using Triumph 765 cc (46.7 cu in) triple engines.
Two-stroke designs are less common in straight-three engines than four-stroke designs, however several were produced by Japanese manufacturers in the late 1960s through to 1980s.
The Kawasaki triple engine was produced from 1968 to 1980 and was used in various road bikes and racing bikes.Most versions were air-cooled, however several were water-cooled. Similarly, the 1972-1980 Suzuki GT series engines were used for both road bike and racing bikes, and were available in both air-cooled and water-cooled versions.
An example of an agricultural application is the Fairbanks-Morse 32E14 low-speed diesel engine, which is shown in the picture to the right coupled to a water pump.
The straight-three layout is common for diesel tractor engines, such as the Perkins AD3.152. This engine was used in the Massey Ferguson 35 and Fordson Dextra tractors, as well as for marine and stationary applications.
The Hewland AE75 is a 750 cc two-stroke aircraft engine that was produced in the mid-1980s. It was an inverted three-cylinder design with liquid-cooling that produced 75 bhp (56 kW).
|Wikimedia Commons has media related to Straight-3 engines .|
A V6 engine is a six-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.
A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.
The straight or inline engine is an internal combustion engine with all cylinders aligned in one row and having no offset. Usually found in four, six and eight cylinder configurations, they have been used in automobiles, locomotives and aircraft, although the term in-line has a broader meaning when applied to aircraft engines, see Inline engine (aviation).
A V4 engine is a four-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.
A straight-twin engine, also known as an inline-twin, vertical-twin, or parallel-twin is a two-cylinder piston engine where two cylinders are arranged in a line along a common crankshaft.
A straight-four engine is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.
The straight-six engine is an internal combustion engine, with six cylinders mounted in a straight line along the crankcase with all the pistons driving a common crankshaft.
The straight-five engine or inline-five engine is an internal combustion engine with five cylinders aligned in one row or plane, sharing a single engine block and crankcase. The justification for a five cylinder engine is that it is almost as compact as an inline-four, and almost as smooth as a straight-six engine.
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".
In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and may be able to operate at higher revolutions per minute (RPM) than a two-valve engine, delivering more power.
The Triumph Triples are a family of modern DOHC inline three-cylinder motorcycle engines made from 1990 onwards by the Triumph Motorcycle Company at their Hinckley, Leicestershire factory. The inspiration for the later triples was the pushrod Triumph Trident, produced from 1968 to 1974 at the Triumph factory at Meriden Works.
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.
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.
The Saab two-stroke was a two-stroke cycle, two cylinder, and later Straight-three engine that Saab based on a DKW design. The first version was 764 cc (46.6 cu in) displacement twin that was transversally mounted in the 1950–1956 Saab 92. It had with 25 hp (19 kW), and a top speed of 100 km/h (62 mph). The 1954 model engine output was raised to 28 hp (21 kW). It had some features only found in modern cars such as one ignition coil per cylinder.
A single-cylinder engine, sometimes called a thumper, is a piston engine with one cylinder. They are often used for motorcycles, motor scooters, go-karts, all-terrain vehicles, radio-controlled  vehicles, portable tools and garden machinery.
The Triumph Daytona 955i is a sport bike manufactured by Triumph from 1997 to 2006. It was powered by a 955 cc (58.3 cu in) liquid cooled, inline three four stroke engine. The bike was launched in 1997 as the Triumph T595 Daytona and renamed Triumph Daytona 955i in 1999.
The Kawasaki triples were a range of 250 to 750 cc motorcycles made by Kawasaki from 1968 to 1980. The engines were air-cooled, three-cylinder, piston-controlled inlet port two-strokes with two exhaust pipes exiting on the right side of the bike, and one on the left. It was the first production street motorcycle with capacitor discharge ignition (CDI). Right from the first triple model, the 1968 Mach III H1 500 cc, it was a sales success that gained a reputation for almost unmatched acceleration as well as an air of danger for inexperienced riders trying to cope with the bike's increased power to weight ratio over any previously available stock motorcycles.
In internal combustion engines, a split-single design is a type of two-stroke where two cylinders share a single combustion chamber.
A big bang engine is an unconventional engine designed so that some of the power strokes occur simultaneously or in close succession. This is achieved by changing the ignition timing, changing or re-timing the camshaft, and sometimes in combination with a change in crankpin angle. The goal is to change the power delivery characteristics of the engine. A regular firing multi-cylinder engine fires at approximately even intervals, giving a smooth-running engine. Because a big-bang engine has uneven power delivery, they tend to run rougher and generate more vibration than an even-firing engine.
V4 replaces straight three
The 1071cc, inline, triple-cylinder configuration produces 803 pounds of thrust and pushes the boat to about 55 mph.
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...
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.
Motivation comes from a 3-cylinder, 650cc petrol engine that kicks out a mere 51bhp (52PS/38kW) and 60Nm (44lb-ft) of torque.
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.