Red marquis at 13:07, 24 May 2010

2010-05-24T13:07:04Z

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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 (e.g. [[Microcars]], [[Kei cars|"light" cars]], and [[City cars]] like the [[Fiat 500]] and [[Mitsubishi Minica]]) 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 [[Honda N360|N360]] and its successors N400 and N600 with straight-two engines in 360cc, 400cc, and 600cc sizes. The [[Honda Z600|Z600]] was produced from 1970 to 1972. From 1958 to 1971, Subaru produced the [[Subaru 360|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 Ferrari|Enzo]] and [[Alfredino Ferrari|Dino Ferrari]] on [[Ferrari Lampredi engine|this design]] but abandoned development due to unsatisfactory balance. It is believed that all the prototypes built simply exploded during tests.

==See Also==
{{Piston engine configurations}}

==External links==
* [http://www.captain.norton.clara.net/cnn2sec14.html A detailed analysis of the effect of different crankshaft offset angles] on the [[engine balance]] of a straight twin engine.

[[Category:Piston engine configurations|Straight-02]]

Straight-two engine - Revision history

Red marquis at 13:07, 24 May 2010