The N series is Honda's first automotive diesel engine, an inline-four for medium-sized vehicles. It uses common rail direct injection, which Honda brands as i-CTDi (Intelligent Common-rail Turbocharged Direct injection). The most notable feature is the aluminium block, which uses proprietary technology in the manufacturing process to provide light weight and high rigidity. Roller chains drive two overhead camshafts. A variable-geometry turbocharger and intercooler are used.