page_title: Inline-four engine
hierarchical_section_title: Inline-four engine
caption_attribution_description: The engine block of the en:Ford I4 DOHC engine (with the cylinder head removed).
context_page_description: The inline-four engine or straight-four engine is a four-cylinder internal combustion engine in which the cylinders are mounted in a straight line or plane along the crankcase. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the pistons driving a common crankshaft. Where it is inclined, it is sometimes called a slant-four. In a specification chart or when an abbreviation is used, an inline-four engine is listed either as I4 or L4.
  The inline-four layout is in perfect primary balance and confers a degree of mechanical simplicity that makes it popular for economy cars. However, it suffers from a secondary imbalance that causes minor vibrations in smaller engines, and more powerful vibrations as engine size and power increase. So, the more powerful engines used in larger cars are generally more complex designs with more than four cylinders.
  Today almost all manufacturers of four-cylinder automobile engines produce the inline-four layout, with Subaru and Porsche 718 flat-four engines being notable exceptions, and so four-cylinder is usually synonymous with and a more widely used term than inline-four.
context_section_description: The inline-four engine or straight-four engine is a four-cylinder internal combustion engine in which the cylinders are mounted in a straight line or plane along the crankcase. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the pistons driving a common crankshaft. Where it is inclined, it is sometimes called a slant-four. In a specification chart or when an abbreviation is used, an inline-four engine is listed either as I4 or L4 (for longitudinal, to avoid confusion between the digit 1 and the letter I).
  The inline-four layout is in perfect primary balance and confers a degree of mechanical simplicity that makes it popular for economy cars. However, it suffers from a secondary imbalance that causes minor vibrations in smaller engines, and more powerful vibrations as engine size and power increase. So, the more powerful engines used in larger cars are generally more complex designs with more than four cylinders.
  Today almost all manufacturers of four-cylinder automobile engines produce the inline-four layout, with Subaru and Porsche 718 flat-four engines being notable exceptions, and so four-cylinder is usually synonymous with and a more widely used term than inline-four. The inline-four is the most common engine configuration in modern cars, with the V6 engine the second most popular. In the late 2000s (decade), due to stringent government regulations mandating reduced vehicle emissions and increased fuel efficiency, the proportion of new vehicles sold in the U.S. with four-cylinder engines (largely of the inline-four type) rose from 30 percent to 47 percent between 2005 and 2008, particularly in mid-size vehicles where a decreasing number of buyers have chosen the V6 performance option.
caption: Ford inline-four engine with cylinder head removed
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