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Cummins 6LTAA8.9-G3 Engine

The Cummins 6LTAA8.9-G3 is a heavy-duty, inline 6-cylinder, 8.9-liter displacement industrial diesel engine primarily utilized as a prime or standby power source for electrical generator sets. Developed as an evolution of smaller engine platforms, it features an elongated stroke, a rigid cylinder block design utilizing replaceable wet liners with mid-stop positioning, and a 4-valve per cylinder head layout. The engine uses a classic Overhead Valve (OHV) configuration driven via lifters, pushrods, and rocker levers from a block-mounted camshaft. To withstand intense mechanical stress and high thermal loading, it incorporates two-piece articulated pistons comprising a forged steel crown and a lightweight cast aluminum skirt. Induction is handled by an exhaust gas turbocharger mated to an air-to-air charge cooling system (LTAA) to optimize air density, fuel efficiency, and emissions control.

The mechanical fuel injection structure relies on a centrally symmetrical arrangement of multi-hole injectors matching the bowl configuration of the articulated steel crowns. High-pressure fuel delivery is provided by an inline BYC P7100 mechanical injection pump. Engine speed control, frequency stability, and governing drop regulation (maintained at 5% or less deviation) are actively managed through an attached GAC Electronic Governor assembly. The maximum allowable inlet suction restriction imposed on the primary fuel lift/transfer pump is 20.3 kPa.

The lubrication system features a full-pressure internal circuitry driven by a gear-type lubricating oil pump. Targeted cooling of the articulated pistons is achieved via dedicated oil spray nozzles positioned in the cylinder block, which direct pressurized lube oil straight into the internal cavity of the piston crown. The oil circuit contains an integrated liquid-to-liquid oil cooler to stabilize thermal breakdown. The maximum allowable oil temperature inside the engine sump is 121C.

Engine cooling utilizes a forced liquid-circulation architecture managed by a high-capacity belt-driven water pump. Thermal regulation is governed by an internal dual-thermostat configuration with an operating control scale range of 82C to 95C. The cooling circuit requires an external radiator pressure cap specifying a minimum relief opening threshold pressure of 70 kPa. For continuous mechanical integrity, the maximum allowable coolant temperature before critical derate or shutdown is 104C under Base/Prime load and peaks at 110C under Standby operation.

General Technical Data

Engine Specifications

Engine Model ............... Cummins 6LTAA8.9-G3
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) ............... 4.49 (114.0)
Engine Stroke, in (mm) ............... 5.71 (145.0)
Displacement, cu.in (L) ............... 543 (8.9)
Rated Engine Power, hp (kW) ............... 335-442 (250-330)
Rated Engine Speed, rpm ............... 1500-2200
Peak Torque ............... 1350-1650 Nm (996-1218 lb-ft) at 1300-1600 rpm
Idle Speed ............... 700-800 rpm
Aspiration Type ............... Turbocharged and aftercooled
Compression Ratio ............... 16.3:1-17.2:1
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 ............... 50-120

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) ............... 53.1-65.0 (1350-1650)
Overall Width, in (mm) ............... 31.5-37.4 (800-900)
Overall Height, in (mm) ............... 47.2-59.1 (1200-1500)
Dry Weight, lbs (kg) ............... 1650-1980 (750-900)

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) ............... 0.012 (0.30)
Exhaust Valve Clearance, in (mm) ............... 0.024 (0.61)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CI-4, CJ-4, CK-4
Engine Oil Capacity, qts (L) .................. 23.1-29.4 (22.0-28.0)
Coolant Capacity, qts (L) ............... 31.5-42.0 (30.0-40.0)

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) ............... 114.00-114.04 (4.488-4.490)
Crankshaft Journal Outside Diameter, in (mm) ............... 97.96-98.00 (3.857-3.858)
Crank Pin Outside Diameter, in (mm) ............... 75.96-76.00 (2.991-2.992)
Crankshaft End Play, in (mm) ............... 0.13-0.38 (0.005-0.015)
Intake Valve Stem Outside Diameter, in (mm) ............... 8.95-8.97 (0.352-0.353)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 8.93-8.95 (0.351-0.352)
Intake Valve Guide Inside Diameter, in (mm) ............... 9.02-9.07 (0.355-0.357)
Exhaust Valve Guide Inside Diameter, in (mm) ............... 9.02-9.07 (0.355-0.357)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.05-0.12 (0.002-0.005)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.07-0.14 (0.003-0.006)
Intake Valve Spring Free Length, in (mm) ............... 62.50 (2.461)
Exhaust Valve Spring Free Length, in (mm) ............... 62.50 (2.461)
Intake Cam Height, in (mm) ............... 51.80-52.40 (2.039-2.063)
Exhaust Cam Height, in (mm) ............... 51.40-52.00 (2.024-2.047)
Piston Pin Outside Diameter, in (mm) ............... 44.99-45.01 (1.771-1.772)
Piston Pin to Piston Bore Clearance, in (mm) ............... 0.01-0.03 (0.0004-0.0012)
Second Ring Side Clearance, in (mm) ............... 0.07-0.12 (0.0028-0.0047)
Oil Ring Side Clearance, in (mm) ............... 0.04-0.08 (0.0016-0.0031)
Top Ring End Gap, in (mm) ............... 0.30-0.55 (0.012-0.022)
Second Ring End Gap, in (mm) ............... 0.60-0.95 (0.024-0.037)
Oil Ring End Gap, in (mm) ............... 0.25-0.55 (0.010-0.022)

Tightening Torque Specs

Cylinder-head bolts ............... 190-210 Nm (140-155 lb-ft)
Main bearing caps ............... 150-180 Nm (111–133 lb-ft)
Connecting rod bolts ............... 70-90 Nm (52–66 lb-ft)
Flywheel bolts ............... 220-260 Nm (162–192 lb-ft)
Crankshaft pulley bolt ............... 240-280 Nm (177–207 lb-ft)
Oil drain plug ............... 30-40 Nm (22–30 lb-ft)
Fuel line nuts ............... 25-30 Nm (18-22 lb-ft)
Water pump bolts ............... 25-30 Nm (18-22 lb-ft)
Timing gear cover bolts ............... 20-25 Nm (15-18 ft-lb)
Injector hold-down ............... 20-25 Nm (15–18 lb-ft)

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• Cummins Engines Specs
  
• Cummins 6LTAA8.9-G2 Specs
  
• Cummins 6LTAA9.5-G1 Specs
  
• Cummins 6T-590 Specs
  
• Cummins 6T-830 Specs
  

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