The vehicles we drive are powered by many engine types (and electric motors, of course) — but perhaps two of the most emotive forms of internal combustion engine are the V and flat configurations.

Flat engines are horizontally-opposed piston engines, and this group includes Boxer engines, but not opposed-piston engines like the Cummins 14.3L Advanced Combat Engine (ACE) designed to power tanks.

Boxer engines feature flat, opposing pistons that move in opposite directions for smooth operation. Subaru and Porsche are primary modern users, benefiting from low center of gravity and performance.