The C Series is an inline, six cylinder, direct injection diesel engine with a bore of 114 mm and stroke of 135 mm, resulting in a displacement of 8.3 liters. The engine was developed to achieve high levels of turbocharging while still maintaining the conservative component loading required to meet aggressive reliability and durability goals. The proliferation of components was held to a minimum to avoid cost and complexity. Ease of adaptability to a variety of off-and-on highway installations, however, was still retained through the design of flexible options.This paper describes the primary components of the engine, and much of the design and development work that led to meeting the technical objectives. Examples of the more interesting mechanical and thermal analyses are also discussed. Combustion and emissions optimzation is described, and various examples of the combustion characteristics are shared.