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Navistar DT engine
Navistar DT engine
Navistar DT engine
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Navistar DT engine
Overview
ManufacturerNavistar International
Production1971–2016 1971–2019 (Mexico) [1]
Layout
ConfigurationInline-6
Displacement360 / 408 / 466 / 530 / 570 cu in (5.9 / 6.7 / 7.6 / 8.7 / 9.3 L)
Cylinder bore4.59 inches
ValvetrainOHV, 2 or 4 valves per cylinder
Combustion
Turbochargervariable and fixed geometry turbocharged
Fuel systemdirect injection and HEUI (hydraulic electronic unit injection)
Fuel typeDiesel
Output
Power output170-350hp (commercial), 375hp military

The Navistar DT (Diesel Turbocharged or Diesel Turbo) engine family is a line of mid-range inline-6 turbo-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 such as school buses, 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 1997 to 2004, the DT was also rebadged and sold by Detroit Diesel as the Series 40.[2][3]

Design

[edit]

The Navistar DT diesel 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 Inc.[4] From 2004 to 2009, the engines use International's Electro-Hydraulic Generation Two (G2) unit injectors.

MaxxForce variants

[edit]

From the time the United States Environmental Protection Agency's 2007 emissions regulations went into effect, the Navistar DT engines were available in three configurations in what turned out to be their final generation prior to discontinuation. These variants were renamed to conform to International's then-new MaxxForce engine brand.

  • MaxxForce DT: 7.6 L (466 cu in) displacement, bore x stroke 4.59 in × 4.68 in (117 mm × 119 mm); with horsepower ratings from 210–300 hp (160–220 kW). The MaxxForce DT was available in standard and high torque configurations.[5]
  • MaxxForce 9: Enlarged variant of the MaxxForce DT, featuring a 9.3 L (570 cu in) displacement, bore x stroke 4.59 in × 5.75 in (117 mm × 146 mm); with horsepower ranging from 300–330 hp (220–250 kW).[6]
  • MaxxForce 10: Same displacement as MaxxForce 9, with horsepower ranging from 310–350 hp (230–260 kW). This engine featured 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.[7]

The engines were also available for defense applications under the MaxxForce D brand. The final generation MaxxForce DT was known as the MaxxForce D7.6I6, and the MaxxForce 10 was known as the MaxxForce D9.3I6. Modifications from the civilian versions included diamond-coated (metal nitride coating) injectors[citation needed] to enable the engines to run on JP-8 fuel.[8]

Electronic injection variants

[edit]
Navistar DT466E
Overview
ManufacturerNavistar International
Production1994-2004
Layout
ConfigurationInline-6 wet-sleeved
Displacement466 cu in (7.6 L)
Cylinder bore4.59 in (116.6 mm)
Piston stroke4.68 in (118.9 mm)
Cylinder block materialCast iron
Cylinder head materialCast iron
ValvetrainOHV 4 valves per cylinder [9]
Combustion
Turbochargerturbocharged
Fuel systemHEUI (hydraulic electronic unit injection)
Fuel typeDiesel
Dimensions
Dry weight1,425 lbs dry
Chronology
PredecessorDT466
SuccessorMaxxForce DT
  • DT 530E 530ST (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 (7.6L): 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 (HEUI).

Mechanical injection variants

[edit]
  • DT 466 Family, Model A175 and A190.
  • DT 408 (6.7L): a smaller version of the DT family.
  • DT 360 (5.9L): 6-cylinder mechanical injection produced from 1987 to 1994[10]
  • 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.

Other Variants:

  • Turbo 400 engine: version used in IH farm and construction equipment, with many different sizes.

Update history

[edit]

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, Exhaust Gas Recirculation with heat exchanger to compensate for improved thermal efficiency, and new four-valve cylinder heads. [1]

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 were renamed MaxxForce DT, MaxxForce 9, and MaxxForce 10, respectively. Among the new features were closed-crankcase ventilation and new wiring harnesses. The MaxxForce engines were first available in the 2008 model year of International trucks and IC Corporation school buses.

In 2010 the DT engines were updated once again for compliance with 2010 emissions standards. They all received new, twin turbochargers, with higher-rated versions of the MaxxForce DT and all MaxxForce 9 and 10 engines receiving intercooling and aftercooling. Upgrades to fuel injectors, the EGR system, and cooling were also part of the 2010 modifications.

2015 was the final production year for the MaxxForce DT. It was discontinued for 2015, with some buses being built as 2016 models. It continued in the RE for the 2016 model. It was announced on July 22, 2016, that the RE will be produced with the Cummins ISL9 and the DT offering was going away completely.

Applications

[edit]
  • Internationa International S series (DT 466)
  • 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
  • International International 3300, 3800, 3900 bus chassis
  • AmTran Corporation Genesis (1992-2002) (DT 360/DT466/DT466E)
  • AmTran Corporation Volunteer/Conventional (DT 360/DT466/DT466E)
  • IC Corporation FE 300 (DT 466/MaxxForce DT)
  • IC Corporation RE 300 (DT 466/MaxxForce DT, DT 570/MaxxForce 9) [MaxxForce DT discontinued]
  • IC Corporation CE 300 (DT 466/MaxxForce DT) [MaxxForce DT discontinued]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Navistar DT engine

View on Grokipedia
from Grokipedia
The Navistar DT engine family consists of mid-range inline-6 turbocharged diesel engines produced by Navistar International Corporation (formerly ), with the DT466 model serving as the flagship variant featuring a 7.6-liter (466 ) displacement and horsepower ratings typically ranging from 170 to 350 hp (130 to 260 kW). Introduced in 1973 by for medium-duty applications, the DT series evolved from mechanical injection systems in early models to advanced electronic controls and emissions-compliant designs by the 2000s, earning a reputation for durability and reliability in demanding environments. Key variants include the original DT466 (1973–1992, 145–260 hp), the updated DT466P (1993–1996, 175–230 hp with improved and systems), and the DT466E (1994–2003, 175–300 hp incorporating HEUI high-pressure electronic injection). In 2007, Navistar rebranded and upgraded the platform as the MaxxForce DT for 2008 model-year vehicles, retaining the wet-sleeve cast-iron block, four valves per cylinder, and in-frame rebuildability while adding twin turbocharging, enhanced EGR for emissions control, and torque outputs up to 860 lb-ft (1,166 Nm); production of the MaxxForce series ended after the 2016 model year. These engines power a wide array of Class 6–8 trucks such as the , WorkStar, and TranStar models, as well as school buses, commercial buses, fire trucks, and construction equipment, with manufacturing having occurred at Navistar's facility until 2018. Notable for their robust design—including six head bolts per and closed-crankcase ventilation—the DT engines have achieved high quality metrics, with low repair rates even after decades of service, making them a staple in fleet operations worldwide.

History and Development

Origins and Early Production

The development of the Navistar DT engine family began in 1967 under (IH), led by Bill Wallace, vice president of the company's Construction Equipment Division, with the goal of creating in-house inline-six diesel engines to replace older V8 designs such as the DVT 573 and support multiple divisions including , trucks, and . Production of the DT series commenced in 1971 at IH's Melrose Park facility in , marking a shift toward more efficient, rebuildable mid-range engines built on a shared architecture for the 300 and 400 series. These early engines featured a cast-iron block and wet-sleeve cylinder liners with high-chrome content, enhancing durability and allowing for field rebuilds without specialized equipment. The inaugural model, the DT466, was introduced in 1973 for agricultural applications, powering IH's 4366 four-wheel-drive tractors, before expanding to on-highway trucks like the Fleetstar in 1975. This inline-six engine had a displacement of 7.6 liters (466 cubic inches), mechanical injection, and power outputs ranging from 170 to 210 horsepower, depending on the application. Its bore and stroke measured 4.30 inches by 5.35 inches, contributing to a robust low-end torque profile suited for medium-duty tasks. Early production emphasized simplicity and reliability, with over 2 million units eventually built across the family, though initial volumes focused on tractors and industrial uses before broader truck adoption by the mid-1970s. In 1986, following IH's rebranding to Navistar International, the DT lineup evolved to include smaller variants for lighter applications, such as the DT360 with 5.9-liter displacement introduced in 1987. The DT408 (6.7 liters) was added later in 1993. These models retained the core mechanical injection system and wet-sleeve design of the DT466, maintaining compatibility with the original architecture while offering scaled power for emerging medium-duty needs. Production continued at facilities in the United States through 2018, supporting global demand for these foundational engines.

Major Emissions and Performance Updates

In 1994, Navistar introduced the Hydraulically actuated Electronically controlled Unit Injector (HEUI) system on the DT engine family, marking a shift from mechanical injection to electronic control for enhanced delivery precision, which improved combustion efficiency and reduced emissions compared to prior mechanical systems. This technology, co-developed with , enabled better atomization and timing control, contributing to compliance with emerging EPA standards while maintaining robust performance in medium-duty applications. By 2004, further updates focused on emissions compliance and airflow optimization, including the adoption of 4-valve-per-cylinder heads to increase and power output. These revisions incorporated (EGR) to lower formation by recirculating inert exhaust gases into the intake, alongside a (VGT) for improved boost response across operating ranges and preparation for (DPF) integration to capture particulates ahead of stricter EPA 2007 standards. The combined effect enhanced and reduced particulate matter without sacrificing the engine's core wet-sleeve architecture. The 2007 rebranding to the MaxxForce DT series emphasized emissions advancements, featuring a maintenance-free closed-crankcase ventilation system that separated oil vapors from blow-by gases using , minimizing unburned hydrocarbons released to the atmosphere. Enhanced cooling systems, including dual EGR coolers, supported higher EGR rates for better control while preventing overheating in demanding conditions. These updates aligned with EPA 2007 on-highway requirements, improving overall durability and fuel economy. For the 2010 model year, enhancements included twin sequential turbochargers to optimize airflow and reduce turbo lag, alongside increased EGR rates for in-cylinder reduction through cooler combustion temperatures. Navistar's approach relied on advanced EGR without initial SCR adoption, aiming to avoid infrastructure, though this led to certification challenges. Power outputs evolved from approximately 210 hp in early 2000s configurations to up to 350 hp by the 2010s, with peak reaching 860 lb-ft (1,166 Nm) to meet heavier load demands. These developments faced significant hurdles, including EPA lawsuits starting in 2010, with ongoing litigation through 2016 alleging that MaxxForce engines failed to meet emissions standards due to EGR system inadequacies, resulting in excess NOx output and necessitating subsequent redesigns, including eventual integration of SCR technology in later updates. The litigation culminated in a 2019 EPA settlement requiring Navistar to pay a $52 million civil penalty, forfeit emission credits, destroy non-compliant engines, and commit to reducing 10,000 tons of NOx emissions, as well as a 2020 class-action settlement of $135 million for affected owners.

Design Features

Core Engine Architecture

The Navistar DT engine family features an inline-6 configuration, providing a balance of power and smoothness for medium-duty applications, with displacements ranging from 5.9 L in the DT360 model to 9.3 L in the DT570 model. This layout consists of six cylinders arranged in a straight line, utilizing an overhead valve (OHV) design with either two or four valves per cylinder depending on the era and variant. The core architecture emphasizes durability and serviceability, making it suitable for demanding commercial and industrial environments. At the heart of the DT engine is a deep-skirt cast-iron block, which provides through its extended skirt design and massive bulkhead sections, weighing approximately 400 lbs on its own for models like the DT466. The cylinders employ wet-liner sleeves made of high-chrome , enabling efficient heat dissipation and allowing for in-frame rebuilds without major disassembly, a key feature for field maintenance. Bore diameters typically range from 4.01 to 4.59 inches, while stroke lengths vary between 4.68 and 5.35 inches across the family, contributing to the displacement differences while maintaining compatibility with shared components. The is forged from and induction-hardened for strength, supported by seven main bearings with line-bored precision to minimize and ensure longevity; connecting rods are also forged with a fractured-cap design for precise alignment and high load capacity. A gear-driven operates the , positioned low in the block for reliability in heavy-duty use. Cooling is achieved through a water-cooled system where the wet sleeves are directly exposed to coolant, promoting uniform and cylinder roundness under load. Lubrication relies on a pressurized oil system with full-flow filtration, often incorporating dual oil filters and a water-to-oil to maintain optimal and extend component life, particularly in high-flow configurations introduced in later updates. For adaptations, certain DT variants were reinforced with stronger components, such as enhanced pistons and internals, to achieve up to 375 hp ratings for specialized applications. The overall dry of DT engines falls between approximately 1,500 and 1,800 lbs, with lengths measuring around 45 to 50 inches, facilitating integration into various designs.

Fuel Injection and Turbocharging Systems

The Navistar DT engine series initially employed mechanical systems prior to 1996, utilizing Bosch inline pumps such as the P3000 or P7100 models, along with rotary distributors in some configurations, where fuel timing was regulated by a mechanical to ensure precise delivery and response. These systems provided reliable direct injection for mid-range diesel applications, supporting power outputs up to 275 horsepower while maintaining compatibility with the engine's wet-sleeve block design for straightforward maintenance. Electronic fuel injection marked a significant progression starting in 1996 with the adoption of the HEUI (Hydraulically actuated Electronically controlled ) system, which lasted through 2004 and used high-pressure engine oil—typically 3,000 to 3,600 psi—to actuate the injectors, multiplying the force to achieve pressures exceeding 21,000 psi for enhanced efficiency. This setup improved atomization and power delivery, enabling ratings from 195 to 250 horsepower in DT466E variants, with the electronic control module optimizing timing based on operating conditions. By 2004, the (Generation 2) injectors refined this HEUI architecture through 2009, featuring advanced designs for better fuel atomization, reduced emissions, and smoother operation across the load range. In the MaxxForce era (from 2007), later models from 2010 integrated common-rail fuel systems for more precise high-pressure fuel delivery up to 30,000 psi, supporting outputs up to 300 horsepower and enhancing overall durability in demanding commercial use. Turbocharging on early DT engines relied on fixed-geometry turbos, such as the Garrett TO4 series, delivering boost levels around 18-20 psi to complement the mechanical injection for baseline performance. From 2004 onward, variable geometry turbos (VGT) were introduced, allowing adjustable vane positioning for improved low-end torque and transient response, with boost ranging 25-35 psi under load. By 2010, twin sequential turbo setups enhanced this further, employing a high-pressure VGT paired with a low-pressure fixed turbo to optimize airflow across the RPM band, reducing lag and boosting low-end torque by up to 15 percent compared to single-turbo configurations. Emissions integration evolved with the addition of EGR coolers post-2007 to recirculate cooled exhaust gases, reducing formation by 20-30 percent in MaxxForce variants, complemented by diesel oxidation catalysts (DOC) for hydrocarbon and CO oxidation. (SCR) systems using injection followed in later implementations to further lower by over 90 percent, integrating seamlessly with the turbo and injection upgrades for compliance with stringent standards.

Engine Variants

Mechanical Injection Models

The mechanical injection models of the Navistar DT engine family represent the early iterations of this inline-six diesel lineup, characterized by their robust, electronically independent designs that prioritized durability and straightforward in medium-duty applications. These variants utilized a Bosch pump-line-nozzle (PLN) mechanical direct system, which delivered reliable performance without the complexity of electronic controls, making them well-suited for trucks, buses, and industrial uses during the late . A fixed-geometry was standard, enhancing power output while maintaining simplicity, and the engines were renowned for their ability to achieve service lives exceeding 500,000 miles with proper . The DT360, with a displacement of 5.9 liters (360 cubic inches), was produced from 1987 to 1993 and served as an entry-level option for lighter-duty vehicles such as delivery trucks and motorhomes. It featured a bore of 4.01 inches and a stroke of 4.75 inches, delivering power outputs ranging from 165 to 190 horsepower at 2,700 rpm and torque between 390 and 485 lb-ft at 1,700 rpm, depending on the configuration and emissions standards. The engine's stamped valve cover and V-belt drive contributed to its compact footprint and ease of service, while updates like a three-piece in 1988 and plasma-coated rings in 1991 improved efficiency and reduced wear. Introduced as a transitional model in 1993 and produced through 1997, the DT408 offered a 6.7-liter (408 cubic inches) displacement to bridge the gap between smaller and larger DT variants, targeting applications requiring moderate power increases. With a bore of 4.301 inches and stroke of 4.680 inches, it produced 175 to 230 horsepower at 2,600 rpm and 430 to 605 lb-ft of at 1,800 rpm, employing a cast aluminum valve cover and for enhanced accessory drive reliability. The DT408 retained the mechanical Bosch injection and fixed turbo setup, ensuring compatibility with existing service tools while providing a step up in capacity for medium-duty trucks. The DT466P, produced from to , was an updated version of the DT466 with improved oil and systems, offering 175 to 230 horsepower. The DT466, at 7.6 liters (466 cubic inches), entered production in 1973 and remained in mechanical form until , forming the backbone of Navistar's heavy-duty offerings with base power ratings from to horsepower at 2,600 rpm and torque spanning 460 to 860 lb-ft at 1,500 to 1,800 rpm. Its design included a deep-skirt cast-iron block for superior strength and a Bosch MW-series injection pump, which supported high-altitude operation up to 10,000 feet with a of 15.5:1. Early models used a stamped valve cover and V-belt , evolving slightly toward belts by the late mechanical phase, and the engine's fixed delivered boost levels up to 18.5 psi for consistent performance in vocational trucks. These mechanical models saw peak production volumes in the , powering a significant portion of and Navistar trucks due to their proven reliability in fleet operations. Production ceased with the implementation of stricter EPA emissions standards in , prompting a transition to electronic injection systems in subsequent variants for improved fuel efficiency and compliance.

Electronic Injection Models

The electronic injection models of the Navistar DT engine family, introduced in the mid-1990s, marked a significant evolution from the mechanical injection variants by incorporating advanced electronic controls and the Hydraulically actuated, Electronically controlled (HEUI) system. This transition enabled precise fuel delivery, improved emissions compliance, and enhanced performance for mid-range applications, with production spanning 1994 to 2006. The HEUI system, which uses high-pressure engine oil to actuate the injectors, allowed for variable injection timing and pressure, optimizing combustion efficiency across varying loads. The DT466E, with a displacement of 7.6 L (466 cu in), was produced from 1994 to 2004 and offered horsepower ratings ranging from 175 to 300 hp at 2,200 rpm, paired with torque outputs up to 860 lb-ft at 1,300 rpm. It featured HEUI injectors and electronic controls for injection timing, which improved responsiveness and power density compared to earlier models. In 2004, the DT466E incorporated (EGR) to meet evolving emissions standards, along with a shift to four-valve-per-cylinder heads for better airflow and efficiency. Bore and stroke dimensions remained at 4.59 in × 5.35 in (117 mm × 136 mm), maintaining the inline-six configuration with a cast-iron block and wet liners. The DT530, an 8.7 L (530 cu in) variant produced from 1995 to 2004, provided 250 to 300 hp at 2,000-2,200 rpm and up to 1,050 lb-ft at 1,200 rpm, emphasizing pull for demanding duties. Its larger displacement was achieved with a bore of 4.59 in (117 mm) and stroke of 5.35 in (136 mm), enabling higher output suitable for heavy-haul scenarios while retaining the HEUI injection and electronic timing controls. This model delivered robust low-end , making it ideal for applications requiring sustained power without excessive rpm. Introduced in 2004 and produced through 2007, the DT570 offered a 9.3 L (570 cu in) displacement for heavy-duty needs, with 280 to 310 hp at 2,200 rpm and from 800 to 950 lb-ft at 1,000-1,200 rpm. The extended stroke of 5.94 in (151 mm) at the same 4.59 in (117 mm) bore provided greater low-speed for severe service, while it adopted four-valve heads to enhance breathing and support EGR integration for emissions control. These features positioned the DT570 as a high- option in the electronic lineup, building on the proven architecture for reliability in extended operations. Central to these models was the Engine Control Module (ECM), which integrated with the HEUI system to manage , timing, and air-fuel ratios based on real-time sensor data. The ECM communicated via a Controller Area Network (, facilitating , fault code retrieval, and integration with vehicle systems for proactive maintenance. This electronic architecture contributed to fuel economy gains of 5-10% over mechanical predecessors through optimized injection events and reduced idle fuel use, while also aiding compliance with emissions regulations. These electronic DT variants inherited the inherent durability of their mechanical forebears, often achieving B50 lifespans exceeding 500,000 miles with proper . However, common reliability concerns included degradation of injector O-rings and seals, which could lead to leaks or if oil quality was neglected, though many engines surpassed 1 million miles in fleet service when seals were routinely inspected and replaced.

MaxxForce Series

The MaxxForce series of engines, introduced by Navistar in 2007, evolved the DT platform to address increasingly stringent U.S. Environmental Protection Agency (EPA) emissions requirements through an emphasis on in-cylinder combustion control and exhaust gas recirculation (EGR) rather than widespread adoption of selective catalytic reduction (SCR) systems in initial designs. These emissions-heavy configurations prioritized high EGR rates to reduce nitrogen oxides (NOx) without urea-based aftertreatment, supplemented by standard diesel particulate filters (DPF) for particulate matter control and closed-breathing positive crankcase ventilation (PCV) systems to minimize hydrocarbon emissions from crankcase gases. This approach aimed to maintain fuel efficiency and simplicity but later drew scrutiny for reliability challenges under real-world conditions. The MaxxForce DT, a 7.6-liter inline-six variant produced from 2007 to 2015, delivered power ratings from 210 to 300 horsepower and up to 860 lb-ft of torque, suitable for medium-duty applications. It incorporated twin sequential turbochargers for improved low-end response and efficiency, alongside an advanced EGR system that recirculated a substantial portion of exhaust gases—approaching 50% in optimized operation—to achieve interim EPA 2007 and 2010 limits of 1.2 g/bhp-hr and below. A DPF was integrated as standard equipment across all ratings, with the closed PCV design routing vapors back into the for rather than venting externally, enhancing overall emissions compliance. Building on this architecture, the MaxxForce 9 offered a larger 9.3-liter displacement for Class 7 trucks, providing 300 to 330 horsepower and 800 to 950 lb-ft of from 2007 to 2016. Similarly, the MaxxForce 10, also 9.3 liters but tuned for severe-duty Class 8 service, generated 310 to 350 horsepower and up to 1,150 lb-ft of during the same period. Later iterations of both models, starting around 2012, incorporated SCR systems with (DEF) to meet full 2010 EPA standards of 0.2 g/bhp-hr , marking a shift from pure EGR reliance amid certification pressures. These variants retained the setup, DPF, and closed PCV for comprehensive aftertreatment. The series' EGR-centric design led to notable controversies, with lawsuits filed between 2012 and 2019 alleging that MaxxForce engines, including the DT, 9, and 10, failed real-world emissions tests by exceeding limits due to EGR cooler failures and system complexity. These legal actions resulted in multimillion-dollar class-action settlements, including buyback programs for affected vehicles and a $52 million to the U.S. Department of Justice and EPA in 2021 for Clean Air Act violations. In response to the issues, Navistar implemented enhanced dyno-testing protocols for emissions validation on subsequent units.

Applications and Production

Commercial and Industrial Uses

The Navistar DT engine family found widespread adoption in medium-duty trucks, powering models such as the International 4300, 7300, and 8500 series, which served applications including delivery, vocational services, and regional haulage. These engines were also integral to the Paystar series of severe-duty trucks, valued for their durability in off-road and heavy-haul scenarios. Across variants, DT engines contributed to International's dominant position, capturing approximately 40% of the Class 6-7 truck market in the 2000s. In the bus sector, DT engines propelled chassis like the IC CE300 and RE series, providing reliable performance for student transport. Manufacturers such as and integrated them into the Genesis model, while Blue Bird utilized DT466 variants in conventional es for enhanced torque in varied routes. For urban transit, the DT466 powered Type D chassis in commercial operations, supporting efficient city and shuttle services. Beyond vehicular uses, DT engines were employed in industrial settings, including farm tractors for agricultural tasks like plowing and harvesting. In construction equipment, they drove loaders and excavators, such as models, offering robust power for earthmoving and . Marine adaptations of the DT466 provided in workboats and auxiliary vessels, with marinized versions featuring cooling modifications for saltwater environments. Military applications featured enhanced DT466 variants delivering up to 375 horsepower. Overall, the DT series exceeded 2 million units in production, underscoring its versatility across commercial, industrial, and defense sectors.

Production Timeline and Discontinuation

The Navistar DT engine traces its origins to , where production began in 1971 with the debut of the DT466 variant for agricultural applications. Following the company's rebranding to Navistar International in 1986, the engine family continued in standard mechanical and early electronic configurations through 2007, powering a wide range of medium-duty trucks and buses. In 2007, Navistar introduced the MaxxForce DT series as an updated emissions-compliant version, produced until its discontinuation in 2014. Over its full lifecycle, Navistar produced more than 2 million DT engines, with peak output occurring in the and amid high demand for medium-duty diesel powertrains. The U.S. phase-out in 2014 stemmed from persistent emissions compliance failures in the MaxxForce DT, exacerbated by Navistar's EGR-only that led to EPA fines, customer lawsuits, and reliability issues like frequent derates and DPF clogging. This prompted a strategic pivot to a Cummins partnership, reintroducing SCR-equipped engines starting in 2013 to meet 2010 EPA standards more effectively. In International trucks, the DT was succeeded by the ISL9 (8.9 L) for medium-duty applications, offering improved and emissions performance without proprietary development risks. For heavier-duty segments, Navistar later adopted its own A26 inline-six (12.4 L) engine in 2017, emphasizing integrated powertrains with up to 4% better fuel economy over predecessors. Post-discontinuation, the DT engine maintains strong aftermarket support, with rebuild kits, remanufactured components, and performance upgrades widely available from suppliers like Interstate-McBee and Maxiforce, ensuring longevity for existing fleets. Early non-emissions-compliant models from the 1970s and 1980s have drawn scrutiny for higher contributions to , though modern rebuilds often incorporate updated controls.

References

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  17. https://www.justice.gov/archives/opa/pr/navistar-inc-reduce-10000-tons-nox-emissions-and-pay-52-million-civil-penalty-federal
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  19. https://landline.media/court-approves-135m-settlement-in-navistar-maxxforce-lawsuit
  20. https://www.fleetrite.com/-/media/Project/Navistar/Fleetrite/Fleetrite/Catalogs/EngineGuide_2019_Final_.pdf?rev=016b782373a5451f8c279485260324a6&hash=66172327FF9B3D8282380B660749F67D
  21. https://tractors.fandom.com/wiki/List_of_International_Harvester_and_Navistar_engines
  22. https://www.aepsurplus.com/upload/attachments/dt466dt530brochure.pdf
  23. https://www.thedieselstore.com/blog/international-dt466-engine-specs
  24. https://www.g2dieselproducts.com/blog-resources/hydraulic-electronic-unit-injector-heui-fuel-system
  25. https://www.skoolie.net/threads/dt466e-and-maxxforce-dt-differences.691640/
  26. https://www.cylinder-heads.com/international-dt466-engine/
  27. https://www.heavydutypros.com/navistar-dt360-torque-and-engine-specifications-esn-thru-39374.aspx
  28. https://www.fleetrite.com/-/media/Project/Navistar/Fleetrite/Fleetrite/Catalogs/EngineGuide_2019_Final_.pdf
  29. https://www.redpowermagazine.com/forums/topic/48985-tell-me-about-the-dt-408/
  30. https://www.slashgear.com/1587605/dt466-engine-diesel-who-makes-navistar-how-much-horsepower-does-produce/
  31. https://www.thedieselstore.com/blog/dt466-vs-dt466e
  32. https://www.prodieselparts.com/navistar-dt466-engine-specifications-application/
  33. https://www.raneystruckparts.com/interstate-mcbee-navistar-dt530-inframe-engine-kit-m-1894140c92/
  34. https://news.international.com/news?item=158
  35. https://aera.org/TB25/TB050125-2.pdf
  36. https://www.scribd.com/document/642884136/DT466-530-2000-2003-Diagnostic-Manual-EGES215-pdf
  37. https://www.accuratediesel.com/dt466-fuel-injector-seal-kit.html
  38. https://www.truckinginfo.com/108780/navistar-details-product-changes-thinking-behind-emissions-strategy-change
  39. https://www.motortrend.com/features/1603-navistar-maxxforce-dt466e/
  40. https://www.rushbuscentres.ca/sites/default/files/files/maxxforcedt-epa-2013.pdf
  41. https://www.navistareducation.com/dotnet/application/downloadcontent2.aspx?flag=&content_id=15174
  42. https://www.ttnews.com/articles/135-million-settlement-approved-navistar-maxxforce-engines-lawsuit
  43. https://www.internationalusedtrucks.com/international-truck-models/medium-duty/durastar/
  44. https://www.schoolbusfleet.com/forum/topic.asp?TOPIC_ID=11856
  45. https://www.youtube.com/watch?v=ce9lKXTqk4Y
  46. https://www.hy-capacity.com/engine/overhaul-kits/major/pid46607/major-overhaul-kit-international-harvester-navistar-dt466-diesel-engine/
  47. https://downeastboatforum.com/threads/marinizing-a-dt466.51741/
  48. https://www.sunstateintl.com/who-makes-international-trucks-lets-take-a-look-behind-the-international-brand-and-how-their-trucks-are-made/
  49. https://www.overdriveonline.com/business/article/14886681/navistar-hit-with-3-lawsuits-over-egr-only-engines-as-carriers-claim-defects-losses
  50. https://www.truckinginfo.com/152785/cummins-and-navistar-reunite
  51. https://www.truckinginfo.com/141577/navistar-to-end-9-10l-engine-production-by-2018
  52. https://www.mobilityengineeringtech.com/component/content/article/47367-navistar-updates-a26-engine-improves-fe-by-4
  53. https://interstate-mcbee.com/products/navistar/
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