Cummins NT855 Specifications
| Engine Model: Cummins NT855 |
| Engine Type: 4-cycle inline 6-cylinder direct injection liquid-cooled diesel |
| Total Displacement: 855 cu.in (14 L) |
| Rated Engine Power: 240-450 Hp (179-336 kW) at 2000 rpm |
| Aspiration Type: Turbocharged |
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The Cummins NT855 is a legendary heavy-duty,
14-liter inline six-cylinder diesel engine known for exceptional
durability, mechanical simplicity, long overhaul life, and reliable
performance in demanding on-road, off-road, industrial, and marine
applications. As part of the Cummins N-Series, the NT855 has been in
service for decades and remains one of the most widely used heavy
commercial engines worldwide.
The NT855 is favored in mining haul trucks, crawler dozers, wheel
loaders, graders, marine vessels, generator sets, and long-haul trucks.
Designed for extreme durability, it can operate continuously at high
load in harsh environments with long service intervals and simple
field-service procedures.
The NT855 is a four-stroke, water-cooled, turbocharged (NT), naturally
aspirated (N), or turbocharged-aftercooled (NTA) inline six-cylinder
diesel engine. Displacement is 14 liters (855 cubic inches). Bore is
approximately 140 mm (5.51 in) and stroke 152 mm (6.00 in), forming a
long-stroke design optimized for torque and fuel efficiency. Compression
ratio ranges from 14.5:1 to 17.0:1 depending on version.
Power ratings:
– Industrial: 240–400 hp (179–298 kW)
– Construction/mining: 300–450 hp (224–336 kW)
– Marine: 240–400 hp (179–298 kW)
– Generator sets: 200–350 kW @ 1,500–1,800 rpm
Peak torque: 1,250–1,650 Nm (922–1,217 lb-ft) @ 1,200–1,500 rpm
Idle speed: 600–700 rpm
Governed speed: 1,800–2,100 rpm
Firing order: 1-5-3-6-2-4.
The NT855 block is heavy cast iron and
includes:
– Wet replaceable cylinder liners
– Deep-skirt construction
– Wide main-bearing saddles
– Full water-jacket cooling
– Reinforced structural ribbing
The wet-liner configuration ensures excellent heat transfer and enables
straightforward overhauls without machining the parent bore.
The NT855 uses six individual cylinder
heads (one per cylinder), each containing:
– Four valves (2 intake, 2 exhaust)
– Direct-injection combustion chamber
– Hardened valve seats
– Replaceable guides
– Mechanical valvetrain
Cold valve lash:
– Intake: 0.36 mm (0.014 in)
– Exhaust: 0.71 mm (0.028 in).
The NT855 uses the Cummins Mechanical PT (Pressure-Time) fuel-injection
system.
Components:
– PT mechanical fuel pump
– Mechanical governor
– Fuel transfer pump
– High-flow injectors
– Dual-stage fuel filtration
Advantages:
– Reliable, simple field service
– Stable delivery across load conditions
– Long-term durability in harsh environments
Fuel-system maintenance:
– Change filters every 250–300 hr
– Drain separator daily
– Injector inspection every 1,500–2,000 hr
– PT pump calibration during major overhaul.
A full-pressure lubrication system is used,
including:
– Gear-driven oil pump
– Full-flow + bypass oil filtration
– Oil jets for piston cooling
Oil capacity: 32–38 liters (34–40 qt)
Oil pressure:
– Operating: 310–450 kPa (45–65 psi)
– Idle: 100–150 kPa (15–22 psi)
Recommended oil:
– SAE 15W-40
– API CI-4, CJ-4, CK-4
Oil-change interval: 250–500 hr depending on duty cycle.
Cooling system includes:
– Gear-driven centrifugal water pump
– Thermostat-controlled coolant passages
– Full water-jacket cooling
– Engine oil cooler
– Radiator or marine heat exchanger
Thermostat:
– Begins opening: 82°C (180°F)
– Fully open: 95°C (203°F)
Cooling capacity: 45–60 liters (47–63 qt)
System pressure: 70–100 kPa (10–15 psi).
| Intake and Exhaust Systems |
Turbocharging:
– Fixed-geometry turbocharger
– High-temperature turbine housing
– Oil-lubricated core
Aftercooling (NTA855):
– Air-to-water charge-air cooling
Air-intake options:
– Single or dual heavy-duty filters
– Optional cyclone pre-cleaner
Exhaust:
– Cast-iron manifold
– High-capacity exhaust elbows.
| Electrical and Starting Systems |
Standard NT855 electrical setup:
– 24V starting system
– 35–70 amp alternator
– Oil-pressure switch
– Coolant-temperature sender
– Flywheel-mounted magnetic pickup
Fully mechanical variants require no ECM.
Depending on application, the NT855 may
include:
– PTO drives
– Hydraulic pump mounts
– Air-compressor drive
– Remote-radiator kits
– Generator housings.
Engine Dimensions:
– Length: 1,500–1,700 mm (59–67 in)
– Width: 1,000–1,200 mm (39–47 in)
– Height: 1,200–1,400 mm (47–55 in)
Dry weight: 1,200–1,400 kg (2,645–3,086 lb).
Routine service intervals:
– Oil + filter: 250–500 hr
– Fuel filters: 250–300 hr
– Air filter: inspect 50–100 hr
– Valve-lash: every 1,000 hr
– Injector test: 1,500–2,000 hr
– Coolant: every 2 years
– Turbo inspection: every major service
– Compression testing: every 2,000 hr.
– Cylinder-head bolts: 350–420 Nm (258–310 lb-ft)
– Main-bearing caps: 550–650 Nm (406–479 lb-ft)
– Connecting-rod bolts: 180–210 Nm (133–155 lb-ft)
– Flywheel bolts: 350–420 Nm (258–310 lb-ft)
– Crankshaft damper bolt: 400–500 Nm (295–369 lb-ft)
– Oil-drain plug: 40–55 Nm (30–41 lb-ft)
– Injector hold-down: 30–40 Nm (22–30 lb-ft).
The Cummins NT855 is used in:
– Mining haul trucks
– Crawler dozers
– Graders
– Wheel loaders
– Agricultural tractors
– Marine propulsion and gensets
– Industrial pumps and compressors
– Construction machinery
– Power-generation units (200–350 kW).
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| Outboard Engines Technical Specifications |
