Cummins NTA 855-G3 Specifications
| Engine Model: Cummins NTA 855-G3 |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 855 cu.in (14.0 L) |
| Rated Engine Power: 375-535 Hp (280-399 kW) at 1800 rpm |
| Fuel System Type: Pressure-Time fuel system |
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The Cummins NTA855-G3 is a 14-liter, inline
6-cylinder, four-stroke diesel engine renowned for its durability and
high power density in generator drive applications. Designed and
manufactured to meet the demands of 60Hz power generation at 1800 RPM,
this engine utilizes turbocharging and aftercooling to achieve
exceptional performance while maintaining fuel efficiency.
The engine incorporates the proven Cummins PT (Pressure-Time) fuel
system, known for its simplicity and reliability. With power ratings
ranging from 280 kW for continuous duty to 399 kW for standby
applications, the NTA855-G3 represents a robust solution for prime
power, standby, and industrial generator sets. Its design emphasizes
serviceability through features such as replaceable wet cylinder liners,
which facilitate engine rebuilding without the need for re-boring the
cylinder block.
Engine Type: 4-Stroke, Inline, 6-Cylinder Diesel
Displacement: 14.0 Liters (855 cu.in)
Bore x Stroke: 140 mm x 152 mm (5.5 in x 6.0 in)
Compression Ratio: 14.0:1
Aspiration: Turbocharged and Aftercooled
Fuel System: Cummins PT (Pressure Time) Direct Injection
Emission Standard: Euro II / Tier II
Firing Order: 1-5-3-6-2-4
Length: 1298 mm (61 in)
Width: 817 mm (32 in)
Height: 1367 mm (53 in)
Governed Speed: 1800 RPM
Idle Speed: 575-650 RPM
Maximum Overspeed Capability: 2700 RPM
Standby Power: 399 kW (535 HP)
Prime Power: 358 kW (480 HP)
Continuous Power: 280 kW (375 HP)
Peak Torque (Prime): 1703 Nm
Peak Torque (Standby): 1896 Nm
Dry Weight: 1315 kg (2900 lbs) for fan-cooled version
Dry Weight: 1420 kg (3130 lbs) for water-cooled version
The cylinder block is constructed from high-grade alloy cast iron,
providing a rigid foundation for all moving components. A defining
feature of this engine is the use of replaceable wet cylinder liners.
These liners are in direct contact with the engine coolant, which
facilitates superior heat dissipation from the combustion area compared
to dry liners.
This design not only improves thermal efficiency and reduces cylinder
bore distortion but also simplifies the overhaul process, as liners can
be replaced without the need to re-bore the engine block. The deep-skirt
design of the block further enhances structural rigidity and supports
the seven main bearings that secure the forged steel crankshaft.
The NTA855-G3 utilizes individual cylinder heads, each serving two
cylinders. These heads are cast from high-strength alloy iron and
feature drilled passages for fuel supply and return lines, eliminating
the need for external fuel lines on the cylinder head. The valve train
incorporates replaceable, corrosion-resistant valve seat inserts and
replaceable valve guides to extend service life and reduce maintenance
costs.
The engine employs a crosshead system for valve actuation, which ensures
that the valve stem is loaded concentrically, reducing side thrust and
wear on both the valve guides and the camshaft followers. The overhead
camshaft arrangement provides precise valve timing control, contributing
to efficient combustion and reliability under heavy load.
The engine is equipped with the Cummins PT (Pressure-Time) fuel system,
a self-adjusting, direct injection system that distinguishes itself from
conventional unit injector or common rail systems. In the PT system,
fuel is circulated under pressure from the fuel pump to the injectors.
The quantity of fuel injected into each cylinder is metered based on
fuel pressure and the time the injector plunger is held open by the
camshaft.
Key features of this system include an integral dual flyweight governor
that provides overspeed protection independent of the main governor,
ensuring safe operation. The camshaft-actuated fuel injectors deliver
precise metering and timing, resulting in efficient combustion, improved
fuel economy, and lower oil dilution. The PT system is recognized for
its simplicity, high-pressure capability, and reliability in demanding
applications.
The lubrication system is a full-flow, pressure-forced type, ensuring
all moving parts receive adequate lubrication under all operating
conditions. A gear-type positive displacement oil pump draws oil from
the sump and circulates it through an oil cooler and a full-flow oil
filter before it is distributed to the engine's critical components.
A bypass valve in the oil filter head prevents interruption of oil flow
if the filter element becomes clogged. The system also includes
dedicated oil passages and spray nozzles for piston cooling, which
direct oil to the underside of the pistons to manage thermal loads.
Total System Capacity (including filter): 38.6 Liters (10.2 U.S. gal)
Oil Pan Capacity (High/Low): 36.0/28.4 Liters (9.5/7.5 U.S. gal)
Oil Pressure at Governed Speed: 241-345 kPa (35-50 PSI)
Minimum Oil Pressure at Idle: 103 kPa (15 PSI)
Maximum Allowable Oil Temperature: 121°C (250°F)
The cooling system is designed to maintain optimal operating
temperatures, utilizing a centrifugal water pump driven by the accessory
drive. Coolant circulates around the wet cylinder liners, through the
cylinder heads, and around the injector sleeves to ensure uniform
cooling of all combustion chamber components.
For turbocharged and aftercooled engines like the NTA855-G3, a separate
coolant circuit directs flow through the aftercooler (or intercooler) to
reduce the temperature of the intake air, increasing its density and
improving combustion efficiency.
Engine-Only Coolant Capacity: 20.8 Liters (5.5 U.S. gal)
System Capacity with Radiator: 60.6 Liters (16.0 U.S. gal)
System Capacity with Heat Exchanger: 49.2 Liters (13.0 U.S. gal)
Standard Thermostat Range: 82-94°C (180-202°F)
Maximum Coolant Temperature: 96°C (205°F)
Minimum Pressure Cap Rating: 48 kPa (7 PSI)
| Intake and Exhaust Systems |
Air Intake System: The turbocharger forces additional air into the
combustion chambers, allowing the engine to burn more fuel and produce
greater horsepower than a naturally aspirated counterpart. The
aftercooler reduces the temperature of the compressed intake air before
it enters the cylinder, further enhancing density and combustion
efficiency.
Exhaust System: The engine is equipped with a wastegated turbocharger
that helps control boost pressure and optimize performance across the
load range. The maximum allowable exhaust backpressure is 10 kPa (3.0 in
Hg), and the recommended exhaust pipe diameter is 127 mm (5.0 in).
The engine features a 24-volt negative ground electrical system. The
standard equipment includes a 24-volt, heavy-duty positive engagement
starter motor and a 35-amp battery charging alternator. The recommended
minimum battery capacity for cold starting (24V system) is 900 Cold
Cranking Amps (CCA).
Overall Dimensions (L x W x H):
Length: 1298 mm (61 in)
Width: 817 mm (32 in)
Height: 1367 mm (53 in)
Dry Weight:
Fan-Cooled Version: 1315 kg (2900 lbs)
Water-Cooled Version: 1420 kg (3130 lbs)
Operating Weight:
Fan-Cooled Version: 1370 kg (3018 lbs)
Water-Cooled Version: 1500 kg (3308 lbs)
Oil Change Interval: Generally recommended every 250-500 hours under
severe duty.
Valve Lash (Intake and Exhaust): 0.36 mm (0.014 in) with engine cold.
Fuel Filter Replacement: Refer to manufacturer's guidelines based on
fuel quality and operating hours.
Coolant: Use a high-quality ethylene glycol-based antifreeze with
supplemental coolant additives (SCA).
Oil Specifications: API classification CD or higher, SAE 15W-40 for most
ambient temperature ranges.
Cylinder Head Bolts: 135 Nm (100 lb-ft) + 90 deg.
Connecting Rod Bolts: 130 Nm (96 lb-ft) + 90 deg.
Main Bearing Cap Bolts: 250 Nm (184 lb-ft) + 90 deg.
Flywheel Housing Bolts: 70 Nm (52 lb-ft).
Injector Hold-Down Clamp: 35 Nm (26 lb-ft).
Rocker Arm Shaft Support Bolts: 35 Nm (26 lb-ft).
The NTA855-G3 engine is primarily designed for generator drive
applications, specifically for prime and standby power generation at
60Hz.
Standby generator sets for hospitals, data centers, and commercial
buildings.
Prime power generators for remote industrial sites, mining operations,
and construction projects.
Continuous duty generator sets for applications requiring uninterrupted
power.
Marine auxiliary generator sets.
Industrial pump drives and other stationary equipment requiring reliable
power.
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