The Napier Deltic was a high-speed, two-stroke diesel engine developed in the United Kingdom by D. Napier & Son in the 1950s. Its most distinctive feature was its triangular (“delta”) layout: three banks of cylinders arranged in a triangle, with three crankshafts—one at each corner—connected by gears. The Deltic used an opposed-piston design, meaning each cylinder contained two pistons moving toward each other without a conventional cylinder head. This configuration made the engine compact, ligh