Stright Two Engine

A straight-two engine, parallel twin or inline twin is a two-cylinder piston engine that has its cylinders arranged in a single row. There are two primary crankshaft configurations for this engine with a new third configuration. One has both pistons moving identically (360° offset) and is commonly called parallel twin. An inline twin or straight-two has one piston moving up as the other moves down (180° offset). The third and new concept offsets the pistons 90° from each other similar to a V-Twin or a crossplane (American) V8.

Straight-two engines regardless of configuration do not use a common crank pin for both cylinders. Even in a parallel twin each cylinder has its own crank pin, they are just set at the same angle.

Automobile use

In the past, straight-two engines have been used in very small cars (eg. Microcars and City cars like the Fiat 500) and in farm equipment, notably by John Deere whose large two-cylinder engines were used in their line of farm tractors up until 1960.

From 1967 to 1972 Honda produced the N360 and its successors N400 and N600 with straight-two engines in 360cc, 400cc, and 600cc sizes. The Z600 was produced from 1970 to 1972. From 1958 to 1971, Subaru produced the 360 with a rear mounted, rear drive 358cc air-cooled engine.

The only current production car to use an inline twin engine is the Tata Nano, announced 10 January, 2008, which has a 623 cc engine with a single balance shaft. Most cars now use at least a straight-3 because of its better power characteristics.

Ferrari briefly considered creating an inline two-cylinder engine for Formula One use in the 1950s. Aurelio Lampredi worked with Enzo and Dino Ferrari on this design but abandoned development due to unsatisfactory balance. It is believed[by whom?] that all the prototypes built simply exploded during tests.Automobile use

Motorcicle Use

In the past, straight-two engines have been used in very small cars (eg. Microcars and City cars like the Fiat 500) and in farm equipment, notably by John Deere whose large two-cylinder engines were used in their line of farm tractors up until 1960.

From 1967 to 1972 Honda produced the N360 and its successors N400 and N600 with straight-two engines in 360cc, 400cc, and 600cc sizes. The Z600 was produced from 1970 to 1972. From 1958 to 1971, Subaru produced the 360 with a rear mounted, rear drive 358cc air-cooled engine.
The only current production car to use an inline twin engine is the Tata Nano, announced 10 January, 2008, which has a 623 cc engine with a single balance shaft. Most cars now use at least a straight-3 because of its better power characteristics.

Ferrari briefly considered creating an inline two-cylinder engine for Formula One use in the 1950s. Aurelio Lampredi worked with Enzo and Dino Ferrari on this design but abandoned development due to unsatisfactory balance. It is believed[by whom?] that all the prototypes built simply exploded during tests.

Source : Wikipedia