Cummins X15N Specifications
| Engine Model: Cummins X15N |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled natural gas |
| Total Displacement: 720 cu.in (11.8 L) |
| Rated Engine Power: 320-400 Hp (239-298 kW) at 2100 rpm |
| Fuel System Type: Natural gas injector |
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The Cummins X12N represents a dedicated natural
gas engine platform engineered for medium- and heavy-duty commercial
vehicle applications. Derived from the proven X12 diesel architecture,
this spark-ignited engine delivers diesel-like performance, reliability,
and durability while operating exclusively on compressed natural gas,
liquefied natural gas, or renewable natural gas.
The X12N is designed to meet the most stringent environmental
regulations, including California Air Resources Board and EPA ultra-low
NOx standards, without the complexity of selective catalytic reduction
or diesel exhaust fluid. Its architecture emphasizes simplified
installation, reduced total cost of ownership, and superior torque
characteristics suited for regional haul, vocational, and refuse
applications.
The engine integrates seamlessly with automated manual transmissions and
features a maintenance-free three-way catalyst aftertreatment system
that eliminates the need for diesel particulate filter regeneration.
With a power range spanning 320 to 400 horsepower and peak torque
reaching 1,250 lb-ft, the X12N provides a viable alternative to diesel
power in applications where emissions compliance, fuel cost stability,
and sustainability objectives converge.
Engine Type: 4-cycle, In-line, 6-cylinder.
Fuel Type: Compressed Natural Gas (CNG), Liquefied Natural Gas (LNG), or
Renewable Natural Gas (RNG).
Displacement: 11.8 Liters (720 cubic inches).
Bore and Stroke: 129 mm x 151 mm (5.08 in x 5.94 in).
Combustion Cycle: Spark-ignited, stoichiometric with cooled exhaust gas
recirculation.
Aspiration: Turbocharged with wastegate and charge air cooling.
Advertised Horsepower: 320 HP to 400 HP (239-298 kW).
Peak Torque: 1,150 lb-ft to 1,250 lb-ft (1,559-1,695 Nm).
Governed Speed: 2,100 RPM.
Engine Braking: Up to 340 braking horsepower via compression release
brake.
The cylinder block is constructed from high-strength gray iron utilizing
a deep-skirt design with cross-bolted main bearing caps to provide
exceptional rigidity and noise, vibration, and harshness attenuation.
The block architecture incorporates a closed-deck design at the cylinder
head interface to enhance sealing integrity under high cylinder
pressures associated with stoichiometric combustion.
The deep-skirt configuration extends the block walls below the
crankshaft centerline, creating a stiff structure that minimizes bore
distortion and maintains consistent piston-to-cylinder clearances across
the operating temperature range. Main bearing bores are machined with a
ladder-frame construction using six bolts per cap to distribute clamping
loads uniformly.
The block integrates a rear gear train housing that simplifies accessory
mounting and reduces overall engine length compared to front-gear train
designs. Cast-in cooling passages are optimized for uniform coolant
distribution around each cylinder liner, with directional flow paths
that prioritize the exhaust valve bridge areas where thermal loading is
greatest. The cylinder block accommodates wet-type replaceable cylinder
liners that allow for service overhaul without block replacement.
The cylinder head is a single-piece gray iron casting with a cross-flow
port configuration that separates intake and exhaust passages to
optimize volumetric efficiency and thermal management. Each cylinder
features four valves arranged in a pent-roof combustion chamber design
that centralizes the spark plug location for consistent flame
propagation.
The intake valves measure 40 mm in diameter, while exhaust valves are 35
mm, both constructed from high-temperature nickel-chromium alloys with
induction-hardened stems and Stellite-faced tips for wear resistance.
Valve seats are precision-inserted powdered metal components with
enhanced thermal conductivity to dissipate combustion heat away from the
valve faces. The overhead camshaft system employs roller finger
followers with hydraulic lash adjusters that maintain zero-valve
clearance across all operating conditions, eliminating the need for
periodic valve adjustments.
Exhaust valve rotators are incorporated to extend valve life by
promoting even heat distribution and preventing localized hot spots. The
cylinder head incorporates integrated exhaust gas recirculation passages
that cool recirculated exhaust gas before entry into the intake
manifold, reducing combustion temperatures and suppressing NOx
formation. Spark plug wells are sealed with O-ring interfaces to prevent
contamination and ensure ignition system reliability in harsh operating
environments.
The fuel system operates as a high-pressure direct-injection spark
ignition architecture with electronic throttle control. A single-stage
fuel pressure regulator reduces stored fuel pressure from either
compressed natural gas or liquefied natural gas sources to a consistent
150 psi delivery pressure at the injector inlet. Six electronically
actuated fuel injectors, one per cylinder, mount directly into the
cylinder head with injector tips positioned to deliver a directed fuel
plume toward the spark plug gap.
Each injector operates independently, allowing cylinder-specific fuel
trim adjustments based on feedback from individual cylinder pressure
sensors and wideband oxygen sensors. The injection timing and duration
are calculated by the engine control module using inputs from the
crankshaft position sensor, camshaft position sensor, manifold absolute
pressure sensor, intake air temperature sensor, coolant temperature
sensor, and exhaust oxygen sensors.
The stoichiometric air-fuel ratio is maintained within a narrow lambda
window of 0.98 to 1.02 across all steady-state operating conditions.
Fuel system components include a high-pressure fuel pump driven by the
rear gear train that pressurizes the fuel rail to 2,900 psi, a fuel rail
with integrated pressure damping, and returnless fuel delivery that
minimizes vapor formation. The electronic throttle control unit manages
air intake through a motor-driven butterfly valve positioned upstream of
the charge air cooler, enabling precise airflow modulation for transient
response and idle stability.
The lubrication system utilizes a high-efficiency gear-type oil pump
mounted to the front of the engine block and driven directly by the
crankshaft gear. The pump incorporates a pressure-regulating valve that
maintains main gallery pressure at 45 psi under normal operating
conditions, with an oil cooler bypass valve that ensures rapid warm-up
during cold starts. Full-flow oil filtration is provided by a spin-on
filter element with a 10-micron nominal filtration rating and a built-in
bypass valve that opens at 25 psi differential pressure to maintain
lubrication during filter restriction conditions.
Oil capacity is 28.5 Liters (7.5 U.S. Gallons) with the standard oil pan
configuration. Oil change intervals are defined by oil quality
monitoring parameters rather than fixed mileage intervals, with maximum
intervals extending to 50,000 miles (80,000 km) under favorable duty
cycles using synthetic 5W-30 or 10W-30 oils meeting Cummins CES 20092
specification.
The lubrication system includes piston cooling jets that direct
pressurized oil to the underside of each piston crown, managing thermal
loading from high-output operation. An integrated oil cooler housing
uses engine coolant as the heat exchange medium to maintain oil
temperatures below 120°C (248°F) under sustained high-load conditions.
The oil pan is constructed from composite material to reduce weight and
provide acoustic damping properties.
The cooling system is designed to manage the heat rejection
characteristics of stoichiometric natural gas combustion, which
generates approximately 15 percent higher thermal load to the coolant
compared to equivalent diesel operation. A centrifugal water pump with
cast-iron housing and composite impeller delivers 450 Liters per minute
(119 U.S. Gallons per minute) of coolant flow at governed speed.
The system incorporates a dual-pass radiator configuration that
maximizes heat transfer efficiency while minimizing frontal area
requirements. Coolant capacity, including engine block, cylinder head,
radiator, and heater circuits, is 38 Liters (10 U.S. Gallons).
Thermostatic control is achieved through a wax-pellet thermostat with an
88°C (190°F) opening temperature and a 95°C (203°F) fully open position.
A separate thermostat-controlled coolant circuit for the charge air
cooler ensures optimal intake air temperature management independent of
engine coolant temperature. The cooling system includes a deaeration
circuit that continuously removes entrained air from the coolant to
prevent cavitation and localized hot spots. Coolant specification
requires a fully formulated ethylene glycol-based antifreeze meeting
Cummins CES 14603 with supplemental coolant additives maintained at 1.5
to 3.0 units per liter to prevent cylinder liner cavitation erosion.
The electrical system operates on a 24-volt architecture with dual
12-volt batteries connected in series, providing 1,500 cold cranking
amps for reliable starting at temperatures down to -29°C (-20°F). The
alternator is a 160-amp brushless unit with integrated voltage
regulation and over-temperature protection. The engine control module is
a high-performance 32-bit processor with 192 MB of internal memory,
managing engine functions including fuel injection, spark timing,
throttle control, aftertreatment monitoring, and diagnostic
communication via J1939 CAN bus protocol.
The air intake system incorporates a dual-stage heavy-duty air cleaner
with radial seal elements rated for 1,200 cfm airflow capacity. Intake
plumbing includes an acoustic resonator tuned to attenuate turbocharger
noise across the operating frequency range.
The exhaust gas recirculation system recirculates 15 to 25 percent of
exhaust gas volume through a cooled loop that reduces combustion
temperatures and suppresses NOx formation. The system includes a
dedicated exhaust gas recirculation cooler with stainless steel tube
construction and a high-temperature pneumatic control valve with
position feedback.
The engine brake system utilizes a compression release mechanism
integrated into the exhaust valve actuation, providing up to 340 braking
horsepower. The system operates in two-stage mode with selectable low
and high braking levels controlled through the vehicle interface.
The aftertreatment system consists solely of a three-way catalyst
packaged within a stainless steel canister mounted directly to the
turbocharger outlet. The catalyst substrate is a ceramic honeycomb
structure coated with platinum, palladium, and rhodium precious metals
that simultaneously oxidize carbon monoxide and unburned hydrocarbons
while reducing nitrogen oxides to nitrogen and water. The system
requires no diesel particulate filter, no selective catalytic reduction,
and no diesel exhaust fluid, eliminating the need for regeneration
events, DEF tank infrastructure, and associated maintenance.
Weight dry: 1,045 kg (2,304 lb) complete engine with standard
accessories and flywheel housing.
Length: 1,295 mm (51.0 in) from fan mounting face to flywheel housing
rear face.
Width: 950 mm (37.4 in) at widest point including turbocharger and
exhaust manifold.
Height: 1,105 mm (43.5 in) from oil pan rail to top of charge air
cooler.
Oil change intervals are determined by the engine control module using
oil quality algorithms that consider fuel consumption, operating hours,
idle time, and oil degradation modeling. Maximum oil change interval:
800 operating hours or 50,000 miles (80,000 km) under favorable duty
cycles. Oil viscosity recommendations: 5W-30 or 10W-30 synthetic meeting
API CK-4 with Cummins CES 20092 approval. Oil filter replacement
frequency: coincident with each oil change.
Spark plug replacement interval: 50,000 miles (80,000 km) or 1,200
operating hours. Spark plug type: Cummins-specific iridium-electrode
design with 0.35 mm gap setting. Coolant replacement interval: 300,000
miles (480,000 km) or 6,000 operating hours using extended-life coolant
meeting CES 14603. Air filter replacement interval: determined by
restriction indicator, maximum restriction 25 inches of water column at
rated airflow.
Valve lash adjustment: not required due to hydraulic lash adjuster
system. Drive belt replacement interval: 150,000 miles (240,000 km) or
3,000 operating hours for serpentine accessory drive belt. Crankcase
ventilation filter replacement interval: 100,000 miles (160,000 km) or
2,000 operating hours. Three-way catalyst: maintenance-free, no required
service intervals.
Cylinder head bolts: 110 Nm (81 lb-ft).
Connecting rod cap bolts: 80 Nm (59 lb-ft).
Main bearing cap bolts: 150 Nm (111 lb-ft).
Flywheel housing to cylinder block: 110 Nm (81 lb-ft).
Flywheel to crankshaft: 170 Nm (125 lb-ft) plus 90.
Exhaust manifold to cylinder head: 44 Nm (32 lb-ft).
Fuel injector clamp: 20 Nm (15 lb-ft).
Spark plug: 28 Nm (21 lb-ft).
Valve cover bolts: 18 Nm (13 lb-ft).
Oil pan bolts: 22 Nm (16 lb-ft).
Water pump mounting bolts: 44 Nm (32 lb-ft).
Starter motor mounting bolts: 80 Nm (59 lb-ft).
Alternator mounting bolts: 50 Nm (37 lb-ft).
Charge air cooler mounting: 44 Nm (32 lb-ft).
Engine mount isolator to block: 180 Nm (133 lb-ft).
The Cummins X12N is engineered for integration into Class 7 and Class 8
commercial vehicles with gross vehicle weight ratings from 26,000 lb to
66,000 lb (11,800 kg to 30,000 kg). Primary applications include
regional haul tractors for pickup and delivery operations, vocational
trucks including concrete mixers and dump trucks, refuse collection
vehicles in front-loader and rear-loader configurations, transit buses
and motor coaches, and specialized equipment such as airport ground
support vehicles and sweepers.
The engine is optimized for use with automated manual transmissions
including the Eaton Cummins Endurant HD series, providing seamless
powertrain integration with shared control algorithms for shift
scheduling and engine braking coordination.
Chassis compatibility is maintained through standardized engine mounting
points consistent with the X12 diesel platform, enabling original
equipment manufacturers to utilize common chassis configurations across
diesel and natural gas product lines. The combination of reduced
aftertreatment system weight, elimination of DEF tank requirements, and
optimized power density results in payload capacity parity with
diesel-powered equivalents in most applications.
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