A Straight-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. The use of a balance shaft in antiphase to that vibration produces a smoothly running engine.

Automobile use

The straight-3 is the smallest engine in use in modern cars, generally for engine displacements of around 1 litre. Cars in the 'super-mini' class often use them on base models, as do the Japanese Keicars. A straight-3 is also used in the Suzuki Swift and they were used in two stroke Saabs 93 - 96. One experimental Saab had two transverse straight-3 engines, the Saab Monster.

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 1198 cc Volkswagen unit seen as the largest petrol unit. A 1.8 L (1779 cc) Diesel was produced by Alfa Romeo for their 1984 33 1.8 TD, the largest straight-3 ever produced.

Motorcycle use

4-stroke :

Triumph, Laverda , Yamaha, BMW.

2-stroke :

Kawasaki, Suzuki

See Also

Straight engine