Flat-4

A flat-4 is a four cylinder internal combustion engine where the cylinders are arranged in a flat configuration. As of today Flat-4 engines are boxer engine, also known as a horizontally opposed engine, in which the corresponding pistons reach top dead centre simultaneously, thus balancing each other with respect to momentum. Flat engines with four or fewer cylinders are most commonly boxer engines. This is not a common configuration, but some brands of automobile have favored such engines and it is a common configuration for smaller aircraft engines such as made by Lycoming or Continental. Although they are considered to be superior to...