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Cummins 6BT5.9-G2 Engine

The Cummins 6BT5.9-G2 is a highly reliable, 5.9-liter, six-cylinder inline engine primarily utilized for prime and standby power generation applications. Known for its robust mechanical design, it features a heavy-duty cast-iron cylinder block and head, which provides long-term durability and resistance to thermal stress. As a turbocharged engine, it delivers high power density with exceptional transient response to sudden load changes. Its simple, fully mechanical design eliminates the need for complex electronic controls, making it easier to maintain and highly dependable in remote or rugged environments. The engine features a cylinder bore of 102 mm (4.02 inches) and a piston stroke of 120 mm (4.72 inches). This square-to-long stroke configuration optimizes torque delivery at low operating speeds.

The engine employs a fully mechanical fuel injection system designed for precise fuel metering and rugged reliability. It features a Bosch inline injection pump (typically the A-pump) paired with mechanical governors to maintain tight speed control. Fuel is delivered through multi-hole, direct-injection nozzles that spray directly into the combustion chamber for optimal thermal efficiency. The system relies on a low-pressure mechanical lift pump to draw fuel through a dual-stage spin-on water separator and fuel filter assembly before it reaches the high-pressure injection circuit.

The system utilizes a gear-driven, high-capacity oil pump to maintain steady oil pressure across all critical components. It has a total oil capacity of 16 liters (4.1 US gallons), which includes the capacity of the spin-on combination full-flow and bypass lubrication filter. The engine features an integrated liquid-to-liquid oil cooler to maintain optimal oil viscosity during continuous operation.

It utilizes a liquid-cooled system driven by a belt-powered jacket water pump. The total coolant capacity of the engine alone is 9.9 liters (2.6 US gallons), requiring additional volume depending on the attached radiator size. Temperature regulation is managed by a heavy-duty thermostat that opens fully at 95C (203F) to redirect flow through the radiator, while an engine-driven cooling fan pulls air across the core to prevent thermal overload.

General Technical Data

Engine Specifications

Engine Model ............... Cummins 6BT5.9-G2
Engine Type ............... 4-cycle inline 6-cylinder direct injection turbocharged liquid-cooled diesel
Number of Cylinders ............... 6
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 4.02 (102.0)
Engine Stroke, in (mm) ............... 4.72 (120.0)
Displacement, cu.in (L) ............... 359 (5.9)
Rated Engine Power, hp (kW) ............... 114-200 (85-150)
Rated Engine Speed, rpm ............... 1500-2500
Peak Torque ............... 420-650 Nm (310-479 lb-ft) at 1300-1600 rpm
Idle Speed ............... 700-800 rpm
Aspiration Type ............... Turbocharged
Compression Ratio ............... 17.5:1
Firing Order ............... 1-5-3-6-2-4
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Full-pressure
Oil Pump Type ............... Gear-driven
Oil Filter Type ............... Full-flow, spin-on
Cooling System ............... Liquid-cooled
Water Pump Type ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System ............... 12V or 24V
Alternator Rating, Amps ............... 35-70

Fuel System

Fuel System ............... Direct injection
Injection Pump Type ............... Rotary or inline
Fuel System Control ............... Mechanical
Governor Type ............... Mechanical
Fuel Injector Type ............... Multi-hole
Fuel Type ............... Diesel Fuel

Dimensions and Weight

Overall Length, in (mm) ............... 41.3-45.2 (1050-1150)
Overall Width, in (mm) ............... 27.6-31.5 (700-800)
Overall Height, in (mm) ............... 39.4-49.3 (1000-1150)
Dry Weight, lbs (kg) ............... 945-1100 (430-500)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 95C (203F)
Cooling system pressure ............... 70-100 kPa (10-15 psi)
Operating oil pressure ............... 300-450 kPa (44-65 psi)
Idle oil pressure ............... 100-150 kPa (15-22 psi)
Intake Valve Clearance, in (mm) ............... 0.254 (0.010)
Exhaust Valve Clearance, in (mm) ............... 0.508 (0.020)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CI-4, CJ-4, or CK-4
Engine Oil Capacity, qts (L) .................. 13.6-16.8 (13.0-16.0)
Coolant Capacity, qts (L) ............... 21.0-26.3 (20.0-25.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Replace fuel filters ............... Every 300 hours
Inspect air filter ............... Every 100 hours
Replace air filter ............... Every 300 hours
Change coolant ............... Every 2000 hours
Valve-lash adjustment ............... Every 1000 hours
Injector inspection ............... Every 1500-2000 hours
Compression test ............... Every 2500 hours
Drain water separator ............... As required
Belt inspection ............... As required

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 4.0165-4.0177 (102.000-102.030)
Crankshaft Journal Outside Diameter, in (mm) ............... 3.2672-3.2682 (82.987-83.013)
Crank Pin Outside Diameter, in (mm) ............... 2.7160-2.7170 (68.987-69.013)
Crankshaft End Play, in (mm) ............... 0.0040-0.0130 (0.102-0.330)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.3129-0.3139 (7.947-7.973)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.3121-0.3131 (7.927-7.953)
Intake Valve Guide Inside Diameter, in (mm) ............... 0.3154-0.3169 (8.011-8.049)
Exhaust Valve Guide Inside Diameter, in (mm) ............... 0.3154-0.3169 (8.011-8.049)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0015-0.0040 (0.038-0.102)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0023-0.0048 (0.058-0.122)
Intake Valve Spring Free Length, in (mm) ............... 1.879 (47.73)
Exhaust Valve Spring Free Length, in (mm) ............... 1.879 (47.73)
Intake Cam Height, in (mm) ............... 1.8482-1.8612 (46.945-47.275)
Exhaust Cam Height, in (mm) ............... 1.8385-1.8540 (46.697-47.091)
Piston Pin Outside Diameter, in (mm) ............... 1.5746-1.5750 (39.995-40.005)
Piston Pin to Piston Bore Clearance, in (mm) ............... 0.0003-0.0007 (0.008-0.018)
Second Ring Side Clearance, in (mm) ............... 0.0027-0.0045 (0.068-0.115)
Oil Ring Side Clearance, in (mm) ............... 0.0015-0.0033 (0.038-0.085)
Top Ring End Gap, in (mm) ............... 0.0100-0.0220 (0.254-0.559)
Second Ring End Gap, in (mm) ............... 0.0100-0.0220 (0.254-0.559)
Oil Ring End Gap, in (mm) ............... 0.0100-0.0220 (0.254-0.559)

Tightening Torque Specs

Cylinder-head bolts ............... 190-210 Nm (140-155 lb-ft)
Main-bearing caps ............... 245-260 Nm (181-192 lb-ft)
Connecting-rod bolts ............... 75-85 Nm (55-63 lb-ft)
Flywheel bolts ............... 135-150 Nm (100-111 lb-ft)
Crankshaft damper bolt ............... 270-300 Nm (199-221 lb-ft)
Oil drain plug ............... 40-50 Nm (30-37 lb-ft)
Injector hold-down ............... 25-30 Nm (18-22 lb-ft)

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• Cummins Engines Specs
  
• Cummins 6B5.9 Specs
  
• Cummins 6BT5.9-G1 Specs
  
• Cummins 6BTA5.9 Specs
  
• Cummins 6BTAA5.9-G12 Specs
  

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