Straight-five engine
inline piston engine with five cylinders
The straight-five engine (also referred to as an inline-five engine; abbreviated I5 or L5) is a piston engine with five cylinders mounted in a straight line along the crankshaft.
Although less common than straight-four engines and straight-six engines, straight-five engine designs have been used by automobile manufacturers since the late 1930s. The most notable examples include the Mercedes Benz's diesel engines from 1974 to 2006 and Audi's petrol engines from 1979 to the present. Straight-five engines are smoother running than straight-four engines and shorter than straight-six engines. However, achieving consistent fueling across all cylinders was problematic prior to the adoption of fuel injection.
Characteristics
Straight-five engines are typically shorter than straight-six engines, making them easier to fit transversely in an engine bay. They are also smoother than straight-four engines, and are narrower than V engines and flat engines.
Engine balance and vibration
Five-cylinder engines have a crankshaft with 72 degree angles. Amongst four-stroke engines, an advantage of engines with five or more cylinders is that the power strokes are overlapping if the engine has an even firing order.
A disadvantage of the odd number of cylinders in a straight-five engine is it results in imperfect primary and secondary engine balance, unlike a straight-six engine which has perfect primary and secondary balance.
The public source identifies “Straight-five engine” as inline piston engine with five cylinders. This brief keeps that definition visible, then builds a research path around Straight-five, engine and inline.
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This entry incorporates text from “Straight-five engine” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.