Cummins L9-350 Specifications
| Engine Model: Cummins L9-350 |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 543 cu.in (8.9 L) |
| Rated Engine Power: 350 Hp (261 kW) at 2200 rpm |
| Fuel System Type: Xtra-High Pressure Injection |
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The Cummins L9-350 represents a culmination of
advanced diesel engineering, positioned as a mid-range powerplant
designed for demanding on-highway and off-highway applications.
This 8.9-liter, 6-cylinder engine is distinguished by its transition to
a fully integrated XPI common rail fuel system, a departure from
previous high-pressure common rail (HPCR) designs, enabling precise
combustion control and elevated power density. Its cornerstone is the
variable geometry turbocharger (VGT), which works in concert with a
sophisticated aftertreatment system to meet stringent EPA 2021/2024 and
Euro VI emissions standards without compromising performance.
The engine is engineered for durability through features like
replaceable wet cylinder liners and a robust single-module
aftertreatment solution that simplifies installation. With a power
output of 350 horsepower and peak torque reaching up to 1,150 lb-ft, the
L9-350 delivers a combination of low-end responsiveness, operational
efficiency, and compact packaging suitable for a wide array of
vocational and regional haul applications.
Engine Type: 4-cycle, In-line, 6-cylinder diesel.
Displacement: 8.9 Liters (543 cu.in).
Bore and Stroke: 114 mm x 145 mm (4.49 in x 5.71 in).
Compression Ratio: 16.8:1.
Advertised Horsepower: 350 HP (261 kW) at rated speed.
Clutch Engagement Torque: 575 lb-ft (780 Nm).
Governed Speed: 2,100 RPM for vocational and high-torque applications.
Governed Speed: 2,200 RPM for regional haul and on-highway applications.
Peak Torque: Two primary ratings are available, selected for
application-specific performance. The productivity rating delivers 1,150
lb-ft (1,559 Nm) from 1,200 to 1,400 RPM. The performance rating
delivers 1,050 lb-ft (1,424 Nm) across the same 1,200-1,400 RPM range.
Aspiration: Variable Geometry Turbocharger (VGT) with an air-to-air
aftercooling system. The VGT provides precise boost control, enhancing
engine braking performance and transient response.
Engine Braking: The VGT-actuated exhaust braking system functions as the
primary engine brake. This system uses the turbocharger’s variable vanes
to create backpressure in the exhaust manifold, providing retarding
power without a separate compression brake mechanism.
The cylinder block is constructed from high-strength gray iron, forming
a deep-skirt design that provides exceptional rigidity and minimizes
bore distortion under high cylinder pressures. This architecture
supports the engine’s high-power density and extends service life.
The block features replaceable mid-stop wet liners. These liners are
installed with a press fit and utilize a mid-stop design to precisely
control their position within the block, ensuring consistent coolant
flow around the liner for uniform thermal management. The wet liner
construction allows for direct coolant contact, enhancing heat
dissipation away from the combustion chamber and facilitating simplified
rebuild procedures.
The cylinder head is a single, high-strength iron casting that covers
all six cylinders. It incorporates a cross-flow design to optimize
airflow efficiency and thermal balance. The head is secured using a
multi-layered steel (MLS) head gasket, which provides a robust seal
under the high clamping loads required for the XPI fuel system.
The valve train consists of four valves per cylinder - two intake and
two exhaust - arranged to centralize the fuel injector for optimal spray
pattern and combustion efficiency. The valve actuation is managed by a
single overhead camshaft (SOHC) driven by gear train from the front of
the engine, utilizing hydraulic lash adjusters to eliminate the need for
periodic valve clearance adjustments.
0The fuel system is the XPI (Xtra-High Pressure Injection) Common Rail
system. Unlike earlier systems, XPI utilizes a high-pressure fuel pump
that generates rail pressures exceeding 2,000 bar (29,000 psi). This
pressure is stored in a common rail accumulator and delivered to
electronically controlled fuel injectors. The system’s primary
distinction is its ability to perform multiple injection events per
combustion cycle - pilot, pre-main, main, and post-injections - with
precise control over timing and duration.
Post-injection events are critical for managing diesel particulate
filter (DPF) regeneration temperatures. The system architecture
eliminates the need for a separate high-pressure fuel line for each
injector, instead using a singular rail that supplies all injectors,
resulting in consistent pressure at all operating conditions.
The lubrication system is a full-flow, forced-feed design utilizing a
rotor-type oil pump mounted internally. The system is engineered to
maintain stable oil pressure across a wide range of operating
temperatures and engine speeds.
Total Oil Capacity: 19 to 32 quarts (18-30 L), with the final volume
determined by the specific oil pan configuration selected for the
chassis application. Operating Pressure: The system maintains a minimum
of 15 PSI at low idle. At rated governed speed, the operating pressure
stabilizes between 35 and 40 PSI.
The cooling system is a pressurized, thermostatically controlled design
that circulates coolant through the cylinder block, cylinder head, and
aftercooler. The engine utilizes a gear-driven centrifugal water pump
for high reliability. The system is designed to accommodate a separate
coolant circuit for the aftertreatment system’s dosing module, ensuring
thermal stability for emissions components.
Cooling capacity is managed by a viscous fan drive, which modulates fan
speed based on coolant temperature, charge air temperature, and air
conditioning system demands to optimize fuel efficiency and thermal
management.
Emissions Technology: The engine utilizes an Integrated Single Module
aftertreatment system. This unit combines the Diesel Oxidation Catalyst
(DOC), Diesel Particulate Filter (DPF), and Selective Catalytic
Reduction (SCR) with urea dosing into a single, compact canister. This
integration simplifies vehicle installation, reduces weight, and
improves thermal management for passive regeneration. The system meets
EPA 2021/2024 and Euro VI emissions standards.
Electronic Control: A single, high-capacity Electronic Control Module
(ECM) manages all engine functions, including fuel injection timing, VGT
position, aftertreatment regeneration, and diagnostic monitoring. This
integrated architecture eliminates the need for separate controllers for
the engine and aftertreatment system, streamlining vehicle wiring and
electronic architecture.
Electrical System: The engine is configured for a 12-volt or 24-volt
electrical architecture, with a high-output alternator (up to 160 amps
or more depending on application) to support the demands of
aftertreatment heating elements, engine controls, and vehicle auxiliary
systems.
Engine Dimensions: 1,097 mm length x 958 mm width x 1,160 mm height
(43.2 in x 37.7 in x 45.7 in). These dimensions represent the engine
long block with standard components, not including the aftertreatment
system or air intake piping.
Weight (Dry): 1,695 lbs (769 kg). This dry weight excludes fluids such
as engine oil, coolant, and fuel.
Aftertreatment Weight: 132-179 lbs (60-81 kg), depending on the specific
Integrated Single Module configuration and mounting hardware selected
for the application.
Standard oil and filter change intervals are established at up to 50,000
miles (80,000 km) or 1,500 hours of operation. These intervals are
contingent upon the use of approved heavy-duty diesel engine oils with
proper viscosity grade and the utilization of genuine Cummins filtration
products. The lubrication system is equipped with a centrifugal bypass
oil filter on certain configurations to further enhance oil cleanliness
and extend component life.
The integrated aftertreatment system features a DPF cleaning interval
aligned with the engine’s operational duty cycle, with ash service
events typically occurring between 250,000 and 400,000 miles
(400,000-640,000 km) for on-highway applications. The engine’s
electronic service tooling allows for real-time monitoring of oil life,
fuel filter restriction, and aftertreatment status to optimize
maintenance scheduling based on actual usage rather than static
intervals.
Cylinder Head Bolts: 110 lb-ft (149 Nm) + 180 deg.
Connecting Rod Bolts: 65 lb-ft (88 Nm) + 60 deg.
Main Bearing Cap Bolts: 100 lb-ft (136 Nm) + 90 deg.
Crankshaft Damper Bolt: 380 lb-ft (515 Nm).
Camshaft Gear Bolt: 110 lb-ft (149 Nm).
Flywheel Housing to Cylinder Block: 50 lb-ft (68 Nm).
Flywheel to Crankshaft: 160 lb-ft (217 Nm).
Fuel Injector Clamp: 55 lb-ft (75 Nm).
Vibration Damper to Crankshaft: 380 lb-ft (515 Nm).
Exhaust Manifold to Cylinder Head: 35 lb-ft (47 Nm).
The Cummins L9-350 is utilized across a broad spectrum of vehicle and
equipment platforms requiring a balance of power, durability, and
compact dimensions.
On-Highway Trucks: Medium-duty and heavy-duty straight trucks for
regional haul, refrigerated delivery, and flatbed applications. It is
also used in certain refuse and dump truck configurations requiring a
shorter engine length for body installation.
Buses: Transit buses, coach buses, and school buses where low emissions,
fuel efficiency, and reliable power are critical for duty cycles with
frequent stops and variable loads.
Construction Equipment: Wheel loaders, excavators, motor graders, and
compactors where the engine’s high torque at low RPM provides necessary
machine performance.
Agricultural Equipment: Self-propelled sprayers, combines, and
high-horsepower tractors requiring a robust power unit for field
operations.
Industrial: Stationary industrial applications such as pumps,
compressors, and material handling equipment, often utilizing the
engine’s ability to be configured for various driven equipment
interfaces.
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