The Navistar DT engine family is a line of mid-range inline-6 diesel engines. With horsepower ratings ranging from 210 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.
The DT engines are of a wet-sleeve design. This means that the cylinder wall (sleeve) is a separately machined part that fits into the cylinder bores cast into the engine block. The cylinder sleeve is in contact with the engine coolant, hence the "wet"-sleeve.
Navistar claims that the wet-sleeve design enhances durability because the consistent wall thickness of the sleeve allows for consistent heat transfer, ensuring the cylinders stay round during thermal expansion. Additionally, they state that the hardened cylinder sleeve is more durable and wear resistant than a softer, cast-in wall. Also, the replaceable cylinder sleeves protect the block from damage (e.g. in case of foreign objects entering the cylinder) and can easily be replaced, which Navistar claims enables simpler restoration to original specifications. The wet-sleeve design also allows the engine to be rebuilt easily to factory specifications, sometimes without even removing the engine from the vehicle.
This design is opposed to parent bore engines, where the cylinder walls are machined out of the bores cast into the block. International states that the uneven thickness of the cylinder walls causes the cylinders to become out of round during thermal expansion, increasing wear. Also, damage to the cylinder wall requires more extensive work to repair.
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. From 2004 to the present, the engines use International's Electro-Hydraulic Generation Two (G2) unit injectors.
The Navistar DT engines are currently available in three configurations. These have been updated to comply with the United States Environmental Protection Agency's new 2007 emissions regulations. These variants have been renamed to conform to International's new MaxxForce engine brand.
Max Force DT: 7.6 liter (466 cubic inches) displacement, bore x stroke 4.59 x 4.68 in (116.5 x 118.9 mm); with horsepower ratings from 210 to 300 hp (220 kW). The MaxxForce DT is available in standard and high torque configurations, which provide extra torque.MaxxForce 9: 9.3 liter (570 cubic inches) displacement, bore x stroke 4.59 x 5.75 in. (116.5 x 146.1 mm); with horsepower ranging from 300 to 330 hp (250 kW). This engine is similar to the MaxxForce DT, but the piston stroke is increased to raise displacement to 9.3 liters.MaxxForce 10: Same displacement as MaxxForce 9, with horsepower ranging from 310 to 350 hp (260 kW). This engine features stronger components, such as steel-crowned two-piece pistons, strengthened engine block, and a titanium turbocharger turbine to cope with the extra power and stress of severe-service and heavy-duty applications.
The engines are also available for defense applications under the MaxxForce D brand. The MaxxForce DT is known as the MaxxForce D7.6I6, and the MaxxForce 10 is known as the MaxxForce D9.3I6. Modifications from the civilian versions include diamond-coated injectors to enable the engines to run on JP-8 fuel.
The DT engine has also historically been available in the following variants; these have all been discontinued.
530E (8.7L); available in standard and high-torque configurations. Replaced in 2004 by DT/HT 570, which were replaced in 2007 by the MaxxForce 9 and 10, respectively. Used electro-hydraulic unit injection.DT 466E: Introduced in 1994, added electronic control to previous, non-electronic DT 466, superseded by model year 2005-and-later DT 466 with variable geometry turbocharger (see below). Also changed over from mechanical fuel injection to electro-hydraulic unit injection.DT 408 (6.7L): a smaller version of the DT family. Used mechanical fuel injection.DT 360 (5.9L): a still-smaller variant. Also used mechanical injection.DTA 360: Same as above, but with an aftercooler, the "A" stands for "aftercooled".DTA 466: Same as earlier mechanical-injection DT 466, but with an aftercooler.Turbo 400 engine: version used in IH farm and construction equipment, with many different sizes.
In 2004, the entire DT family of engines was updated to meet 2004 emissions standards set out by the United States Environmental Protection Agency. Changes to the engines included a new turbocharger (called EVRT, for "Electronic Variable Response Turbocharger") with movable turbo vanes to improve boost and reduce lag, a new, electronically-controlled hydraulic unit fuel injection system, cooled Exhaust Gas Recirculation to reduce emissions, and new four-valve cylinder heads.
In 2007, the DT engines were updated once again to comply with stricter 2007 emissions standards. The DT 466, DT 570, and HT 570 engines will be renamed MaxxForce DT, MaxxForce 9, and MaxxForce 10, respectively. New features include closed-crankcase ventilation and new wiring harnesses. The MaxxForce engines are available in model year 2008 International trucks and IC Corporation school buses.
International CXT (DT 466/MaxxForce DT) International 8500 (HT 570) International 7300, 7400, 7500 (DT 466, DT 570, HT 570) International 4300, 4400 (DT 466/MaxxForce DT, DT 570/MaxxForce 9) International MaxxPro IC Corporation FE 300 (DT 466/MaxxForce DT) IC Corporation RE 300 (DT 466/MaxxForce DT, DT 570/MaxxForce 9) IC Corporation CE 300 (DT 466/MaxxForce DT)