Boxermotors

Boxermotors, commonly known in English as boxer engines, are a type of internal combustion engine with horizontally opposed cylinders. In this layout, cylinders are arranged in pairs on opposite sides of a central crankshaft, and pistons of each pair move toward and away from each other in opposite directions. The design is valued for its smooth operation and balanced forces, contributing to reduced vibration and a low overall center of gravity.

Design and operation

Boxer engines use a single crankshaft with opposing cylinders. The opposing piston motion cancels much of the primary and secondary forces, yielding smooth idling and refined running. The flat configuration can be air- or liquid-cooled, and the engine is typically wider and shorter than an inline counterpart. The layout allows a low hoodline and favorable weight distribution, which can enhance handling in cars and stability in aircraft.

Variants and applications

Boxermotors are built in 2-, 4-, 6-, and 8-cylinder configurations, with the most common automotive examples being flat-four and flat-six layouts. They are widely used in automobiles by brands such as Subaru (notably flat-four engines) and Porsche (notably flat-six engines in the 911). Boxers have also seen extensive use in light aircraft and motorcycles, where compact dimensions and smoothness are advantageous.

Advantages and drawbacks

Advantages include excellent balance, low center of gravity, and smooth operation. Drawbacks include a wider engine footprint, potentially higher production costs, and more complex servicing in some designs.

Notable examples

Porsche 911 flat-six engines, Subaru flat-four engines, and various aircraft engines of the horizontally opposed family illustrate the boxer's long-standing influence in both automotive and aviation engineering.