Cummins ISX-550 Specifications
| Engine Model: Cummins ISX-550 |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 912 cu.in (14.9 L) |
| Rated Engine Power: 550 Hp (410 kW) at 2100 rpm |
| Fuel System Type: High-Pressure Injection |
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The Cummins ISX-550 represents the pinnacle of
the heavy-duty ISX series, an engine family renowned for its dominance
in the North American on-highway trucking sector. Designed for long-haul
applications demanding maximum performance, this 14.9-liter, inline-6
configuration was engineered to deliver a compelling balance of brute
strength and sophisticated emissions control.
The engine’s evolution is marked by significant technological shifts,
moving from dual overhead camshafts to a single overhead cam design, and
transitioning from high-pressure unit injectors to an advanced
common-rail fuel system. The ISX-550 is distinguished by its substantial
torque curve, delivering peak pulling power at a low 1,200 RPM, which
allows for exceptional drivability and fuel efficiency when paired with
optimized transmission gearing.
Its robust construction, featuring a deep-skirt block and replaceable
wet liners, ensures the structural integrity required for sustained
high-output operation. The integration of the Intebrake, an integrated
compression brake system, provides vehicle control that complements its
considerable power output. This engine is a testament to Cummins’
engineering focus on meeting stringent EPA emissions standards without
compromising the reliability and performance expected by owner-operators
and fleet managers.
The ISX-550 is a 4-cycle, In-line, 6-cylinder diesel engine. Its
displacement measures 14.9 Liters (912 cu.in), achieved through a bore
and stroke of 137 mm x 169 mm (5.39 in x 6.65 in). The engine’s
configuration varies by production era: pre-2010 models utilize a Dual
Overhead Cam (DOHC) arrangement with four valves per cylinder, while
2010 and later models employ a Single Overhead Cam (SOHC) design, also
with four valves per cylinder. The aspiration system is a Variable
Geometry Turbocharger (VGT) with electric actuation, optimizing air
delivery across the RPM range. The firing order is 1-5-3-6-2-4.
Advertised horsepower is 550 HP (410 kW). Peak torque is rated at 1,850
lb-ft (2,508 Nm), achieved at 1,200 RPM. The governed speed range is
2,000-2,100 RPM, with clutch engagement torque specified at 1,000 lb-ft
(1,356 Nm). The engine braking system is the Intebrake, an integrated
design that provides up to 600 braking horsepower for enhanced vehicle
control.
The cylinder block is constructed from high-strength gray iron,
featuring a deep-skirt design that extends the cylinder walls below the
crankshaft centerline. This configuration enhances the block’s rigidity
and reduces noise, vibration, and harshness. The block incorporates
replaceable mid-stop wet liners.
These liners are centrifugally cast for uniform strength and feature a
mid-stop shoulder that ensures precise seating and proper sealing within
the block’s coolant jacket. The deep-skirt structure, combined with
cross-bolted main bearing caps, provides a stable foundation for the
crankshaft, essential for managing the high cylinder pressures generated
by the engine’s advanced fuel and turbocharging systems.
The cylinder head is a single casting in the SOHC configuration or dual
castings in the DOHC configuration, both made from high-strength alloy
cast iron. It houses four valves per cylinder - two intake and two
exhaust - which optimize airflow for efficient combustion and improved
thermal efficiency. In the DOHC design, separate camshafts actuate the
intake and exhaust valves, allowing for variable valve timing strategies
in earlier models.
The SOHC design, used in later emissions-compliant versions, utilizes a
single camshaft with a combination of rocker arms and crossheads to
operate the four valves per cylinder. Valve bridges ensure even loading
across the paired valves. The valvetrain is designed to withstand the
mechanical demands of the high-pressure fuel system and the Intebrake,
with hydraulic lash adjusters providing automatic clearance maintenance
and reducing routine service intervals.
The fuel system on the ISX-550 evolved significantly over its production
life. Earlier models utilized a High-Pressure Injection (HPI) unit
injection system. In this design, each cylinder had its own unit
injector actuated by the engine’s camshaft. These injectors generated
injection pressures up to 30,000 PSI.
Later models, specifically those designated CM2250 and CM2350,
transitioned to the XPI (Xtra-High Pressure Injection) common-rail
system. This system utilizes a high-pressure fuel pump that delivers
fuel to a common rail accumulator at pressures reaching up to 35,000 PSI
(2,413 bar). Electronically controlled injectors, capable of multiple
injection events per cycle, are supplied from this rail.
This common-rail architecture allows for precise control over injection
timing, duration, and pressure, enabling advanced combustion strategies
that reduce noise and particulate matter while optimizing fuel
consumption. All systems are managed by the engine’s electronic control
module (ECM), which adjusts parameters based on load, speed, and
operating conditions.
The lubrication system is a forced-feed, full-flow filtration type. The
oil pump is a gear-type pump mounted on the front of the engine, driven
by the gear train. Total oil capacity ranges from 13-14 U.S. Gallons
(49.2-52.9 L), contingent on the specific oil pan selected for the
vehicle application. Operating oil pressure specifications are 15 PSI at
low idle, rising to 35-40 PSI at rated governed speed under normal
operating temperatures.
The system incorporates a centrifugal bypass oil filter in addition to
the full-flow spin-on filters, providing extended oil cleanliness and
contributing to longer oil change intervals. A piston cooling jet system
directs oil to the underside of the piston crowns for thermal
management.
The cooling system is a pressurized, closed-loop design utilizing a
centrifugal water pump driven by the gear train. The thermostat begins
opening at 82°C (180°F) and achieves full travel at 93°C (200°F). The
system requires fully-formulated antifreeze, either ethylene glycol or
propylene glycol based, meeting TMC RP 329 (for conventional coolants)
or RP 330 (for extended-life coolants) specifications.
Coolant flow is directed through the block and cylinder head in a
reverse-flow pattern in some configurations, with coolant first entering
the cylinder head to provide superior cooling to the hottest areas
around the injector and exhaust valve seats. The engine-mounted
gear-driven fan is controlled electronically based on coolant
temperature, intake manifold temperature, and air conditioning system
pressure.
Emissions Technology: The ISX-550 employs a multi-faceted approach to
emissions control to meet EPA standards. The system includes Cooled
Exhaust Gas Recirculation (EGR), which routes a portion of inert exhaust
gas back to the intake manifold to lower combustion temperatures and
reduce NOx formation. The cooled EGR system incorporates an EGR cooler
and a differential pressure valve for precise flow control. For
particulate matter, a Diesel Particulate Filter (DPF) is used to trap
soot, which is periodically oxidized through passive and active
regeneration. Later configurations incorporate Selective Catalytic
Reduction (SCR), where Diesel Exhaust Fluid (DEF) is injected into the
exhaust stream to convert remaining NOx into nitrogen and water vapor.
These systems work in concert under the supervision of the engine’s
aftertreatment control module.
Intake and Exhaust: The intake manifold is designed to distribute air
evenly to all six cylinders. The Variable Geometry Turbocharger (VGT)
uses electronically controlled vanes to adjust the flow of exhaust gas
to the turbine wheel, allowing for rapid boost response at low RPM and
controlled back pressure for exhaust braking and regeneration events.
Electrical System: The engine is equipped with a 24-volt starting
system, utilizing two 12-volt batteries connected in series. The
charging system consists of a high-output, brushless alternator,
commonly rated between 140 and 200 amperes, depending on the chassis
application.
The dry weight of the engine is 3,021 lbs (1,370 kg). The system weight,
which includes fluids such as oil, fuel, and coolant, is 3,093 lbs
(1,403 kg). Overall dimensions are dependent on the specific fan,
flywheel housing, and accessory configuration. A common long-haul
configuration yields an length of 54 in (1,372 mm), a width of 36 in
(914 mm), and a height of 48 in (1,219 mm). The center of gravity is
positioned low within the block due to the deep-skirt design and
crankshaft placement.
Oil and filter change intervals are determined by the Cummins Oil
Maintenance System, with high-mileage fleets achieving intervals up to
50,000 miles (80,467 km) under favorable conditions. The fuel filter and
water separator require replacement at standard service intervals, with
the system including a water-in-fuel sensor. The centrifugal bypass oil
filter requires servicing at designated intervals, often alternating
with the full-flow filters.
The coolant filter with integrated supplemental coolant additives (SCA)
is replaced on a scheduled basis to maintain coolant chemistry. Valve
lash adjustment, where applicable, is recommended at intervals
determined by the ECM, with the hydraulic lash system in later models
eliminating the need for manual adjustments. The Intebrake lash requires
periodic inspection and adjustment as part of the valvetrain
maintenance.
Cylinder Head Bolts (SOHC): 100 lb-ft (135 Nm).
Connecting Rod Bolts: 80 lb-ft (108 Nm).
Main Bearing Cap Bolts (Vertical): 150 lb-ft (203 Nm).
Main Bearing Cap Bolts (Horizontal): 85 lb-ft (115 Nm).
Flywheel Housing to Block: 40 lb-ft (54 Nm).
Flywheel to Crankshaft: Torque to 140 lb-ft (190 Nm).
Intake Manifold Bolts: Torque to 35 lb-ft (47 Nm).
Exhaust Manifold Bolts, Stage 1: 40 lb-ft (54 Nm).
Exhaust Manifold Bolts, Stage 2: 52 lb-ft (70 Nm).
Fuel Injector Clamp (Unit Injector): 60 lb-ft (81 Nm).
Fuel Rail Mounting Bolts (Common-Rail): 18 lb-ft (24 Nm).
The Cummins ISX-550 was primarily designed for the North American Class
8 on-highway truck market.
Freightliner Cascadia and Century Class: Used as a high-horsepower
option for line-haul and heavy-load operations.
Kenworth T660, T680, and W900: Specified for heavy-haul and long-haul
applications requiring maximum torque.
Peterbilt 386, 387, and 389: Selected for owner-operators and fleets
prioritizing high performance and resale value.
International ProStar and 9900i: Utilized as a premium engine option in
International’s flagship on-highway models.
Volvo VNL and VNM: Offered as an alternative to Volvo’s proprietary
D-series engines in certain model years.
Specialty Applications: The engine also saw service in severe-service
motorhomes, custom emergency vehicles, and certain agricultural and
industrial equipment where a compact, high-torque density power unit was
required.
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