The Navistar DT engine family is a line of mid-range inline-6 diesel engines. With horsepower ratings ranging from 170 hp (130 kW) to 350 hp (260 kW), the Navistar DT engines are used primarily in medium-duty truck and bus applications, although some versions have been developed for heavy-duty regional-haul and severe-service applications. Prior to 1986 Navistar International, then known as International Harvester Company, used the DT engine in farm and construction equipment.
From 1984 until late 1995, the DT engines used a Bosch pump-line-nozzle (PLN) mechanical direct fuel injection system. 1984 through 1992 DTs used a Bosch MW style pump, while the 1993-1995s used a Bosch P style pump, and starting what was called New Generation Diesel engine design, which is still the same basic block design. Mechanical injection was still utilized in trucks up into the 1997 year, but this is rare. In 1994, due to tightening emissions regulations, the engines were redesigned to use electronically-controlled unit direct fuel injection. From 1994 to 2004, the engines used HEUI (Hydraulically-actuated Electronically-controlled Unit Injection) injectors, co-developed by Navistar and Caterpillar. [1] From 2004 to the present, the engines use International's Electro-Hydraulic Generation Two (G2) unit injectors