Please improve this article if you can. (July 2008)
A straight-3 or inline-3 is an internal combustion engine with three cylinders arranged in a straight line side by side.
Most straight-3 engines employ a crank angle of 120° and are thus 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. The use of a balance shaft in antiphase to that vibration produces a smoothly running engine.
An exception to the 120° crankshaft can be found in some of the straight-3 engines made by motorcycle manufacturer Laverda. In these engines, sometimes referred to as 180° triples, the outer pistons rise and fall together like a 360° straight-2. The inner cylinder is offset 180° from the outer cylinders. In these engines cylinder 1 fires, 180° later cylinder 2 fires, and then 180° later cylinder 3 fires. There's no power stroke on the final 180° of rotation—much like a 4-cylinder engine that's missing the fourth cylinder.
The smallest straight-3 engine was the 543 cc Suzuki F5A used in the 1982 Cervo. Smart currently produces a diminutive 799 cc diesel straight-3, the smallest ever. Most straight-3 engines fall below 1.2 liters, with a 1,198 cc Volkswagen unit seen as the largest petrol unit. A 1.8 L (1779 cc) diesel was produced by VM Motori to 1984 Alfa Romeo 33 1.8 TD, the largest straight-3 produced for automotive use. Straight-3 engine are also used in a some of Daihatsu cars. The Daihatsu Charade and the Cuore used or are still fitted with this engine type. The 3 cylinder 1.0 liter Daihatsu Diesel engine was also available with a turbo charger.
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This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (July 2008) |
4-stroke:
Aprilia, Laverda, Triumph, Yamaha, BMW.
The Triumph Rocket III has a 2,294 cc straight-3 engine, currently the largest engine in a motorcycle being made by a major manufacturer.
2-stroke :
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