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Mitsubishi K3G Engine

The Mitsubishi K3G is a compact, industrial-grade 4-cycle, water-cooled, vertical 3-cylinder diesel engine. Characterized by its overhead valve configuration and highly efficient direct injection combustion system, this engine is engineered for heavy-duty applications in agricultural machinery (such as the Mitsubishi MT205 tractor) and mini-excavators. The K3G utilizes a heavy-cast iron block with a firing order of 1-3-2 and a robust compression ratio designed to deliver high torque at low operating speeds while meeting strict durability standards under continuous duty cycles.

Valve Configuration: The engine features an overhead valve (OHV) arrangement operated via pushrods and rocker arms from a single gear-driven camshaft within the cylinder block. Valve lash adjusting screws are located at the rocker arm assembly to allow standard maintenance adjustment. Internal cylinder dimensions feature a bore of 82 mm and a stroke of 78 mm, yielding a total displacement of 1.236 liters. The standard compression ratio is 18:1.

Fuel System Description: Fuel delivery is executed via a high-pressure direct injection combustion chamber design. The system uses a dedicated Bosch M-type inline injection pump timed precisely to the engine firing order. High-pressure fuel lines deliver fuel to DLL-P type injection nozzles, which feature a factory-set cracking/opening pressure of 220 kg/cm2 for clean fuel atomization directly into the piston crowns.

Lubrication: Forced lubrication is managed via a high-capacity trochoid oil pump integrated into the timing gear case. The lubrication circuit is protected by an internal oil pump check valve with a rated opening pressure of 4 kg/cm2 to manage oil line pressures and safeguard major mechanical clearances. Cooling: Temperature management uses a pressurized forced recirculation cooling system. A belt-driven centrifugal water pump circulates coolant through the cylinder block and cylinder head passages, governed by a pellet-type thermostat to maintain standard engine operating temperatures under variable loads.

General Technical Data

Engine Specifications

Engine Model ............... Mitsubishi K3G
Engine Type ............... 4-cycle vertical 3-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.23 (82.0)
Engine Stroke, in (mm) ............... 3.07 (78.0)
Displacement, cu.in (L) ............... 75.4 (1.236)
Rated Engine Power, hp (kW) ............... 20.0 (14.9)
Rated Engine Speed, rpm ............... 2500
Peak Torque ............... 44.2 lb-ft (60.0 Nm) at 1600 rpm
Idle Speed ............... 800-900 rpm
Aspiration Type ............... Naturally Aspirated
Operating Speed ............... 2500 rpm
Compression Ratio ............... 18.0:1
Firing Order ............... 1-3-2
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Forced pressure lubrication
Oil Pump Type ............... Trochoid gear-driven pump
Oil Filter Type ............... Full-flow spin-on element
Cooling System ............... Liquid-cooled with radiator
Water Pump Type ............... Belt-driven centrifugal pump
Air Cleaner Type ............... Dry dual-stage element
Starting System ............... Electric Starter Motor
Electrical System ............... 12V
Alternator Capacity, V-A ............... 12-35
Starter Motor Rating, hp (kW) ............... 1.6 (1.2)

Fuel System

Fuel Injection Pump Type ............... Bosch M mini type inline pump
Fuel Injection Nozzle Type ............... Multi-hole type nozzle
Fuel Type ............... Diesel fuel No.2-D
Governor Type ............... Centrifugal flyweight mechanical
Fuel Feed Pump Type ............... Mechanical diaphragm
Fuel Filter Type ............... Spin-on cartridge type paper element
Injection Timing, deg ............... 16.0 BTDC
Injection Opening Pressure, psi (bar) ............... 1991.0 (137.3)
Maximum No-Load Speed, rpm ............... 2750
Minimum Fuel Delivery Rate, cc/stroke ............... 0.024
Fuel Tank Leakage Standard, psi (bar) ............... 0.0 (0.0)
Fuel Return Line Diameter, in (mm) ............... 0.24 (6.0)
Fuel Inlet Line Diameter, in (mm) ............... 0.31 (8.0)

Dimensions and Weight

Overall Length, in (mm) ............... 22.4 (570)
Overall Width, in (mm) ............... 18.1 (460)
Overall Height, in (mm) ............... 23.8 (605)
Dry Weight, lbs (kg) ............... 254 (115)

Maintenance Data

Service Information

Compression Pressure, Standard, psi (bar) ............... 426.7 (29.4)
Compression Pressure, Limit, psi (bar) ............... 355.6 (24.5)
Compression Pressure Between Cylinders, psi (bar) ............... 35.6 (2.5)
Oil Pressure at Rated Speed, psi (bar) ............... 42.7-56.9 (2.9-3.9)
Oil Pressure at Idle Speed, psi (bar) ............... 14.2 (1.0)
Thermostat Opening Temperature, F (C) ............... 160.0 (71.0)
Thermostat Full Open Temperature, F (C) ............... 185.0 (85.0)
Fan Belt Deflection, Standard, in (mm) ............... 0.39 (10.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.010 (0.25)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.010 (0.25)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30W, SAE 10W-30, or 15W-40
API Service Classifications ......................... CD or Higher
Engine Oil Capacity, Upper Limit, qt (L) ............... 4.2 (4.0)
Engine Oil Capacity, Lower Limit, qt (L) ............... 3.0 (2.8)
Coolant Fluid Capacity, qt (L) ............... 4.8 (4.5)

Service Intervals

Change oil and filter ............... Every 200 hours
Inspect air cleaner ............... Every 100 hours
Replace air cleaner ............... Every 1000 hours
Replace fuel filter ............... Every 400 hours
Valve clearance adjustment ............... Every 500 hours
Fuel system inspection ............... Every 500 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 1000 hours
Clean radiator core ............... Every 250 hours
Inspect belt tension ............... Every 250 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 3.2283 (82.000)
Cylinder Block Top Surface Flatness, in (mm) ............... 0.0020 (0.050)
Cylinder Head Bottom Surface Flatness, in (mm) ............... 0.0020 (0.050)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.9059 (23.010)
Connecting Rod Big End Side Play, in (mm) ............... 0.0039-0.0138 (0.100-0.350)
Crankpin Bearing Oil Clearance Standard, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Main Journal Outer Diameter, in (mm) ............... 2.0472 (52.000)
Crankpin Journal Outer Diameter, in (mm) ............... 1.7717 (45.000)
Main Journal Bearings Oil Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Crankshaft End Play, in (mm) ............... 0.0020-0.0098 (0.050-0.250)
Piston Outer Diameter, in (mm) ............... 3.2252 (81.920)
Piston to Cylinder Wall Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.9055 (23.000)
Piston Pin Outer Diameter, in (mm) ............... 0.9053 (22.995)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0001-0.0004 (0.002-0.011)
Piston Pin to Con Rod Small End Clearance, in (mm) ............... 0.0004-0.0010 (0.010-0.025)
Top Ring Groove Width, in (mm) ............... 0.0787 (2.000)
Second Ring Groove Width, in (mm) ............... 0.0787 (2.000)
Oil Ring Groove Width, in (mm) ............... 0.1575 (4.000)
Top Ring Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Second Ring Side Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Oil Ring Side Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Top Ring End Gap, in (mm) ............... 0.0079-0.0138 (0.200-0.350)
Second Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Oil Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2736 (6.950)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2724 (6.920)
Valve Guide Inner Diameter, in (mm) ............... 0.2756 (7.000)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0012-0.0024 (0.030-0.060)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0020-0.0033 (0.050-0.085)
Valve Seat Width, in (mm) ............... 0.0472-0.0591 (1.200-1.500)
Valve Margin Thickness, in (mm) ............... 0.0394 (1.000)
Valve Face Angle, deg ............... 45.0
Valve Seat Angle, deg ............... 45.0
Valve Spring Free Length, in (mm) ............... 1.6378 (41.600)
Camshaft Journal Outer Diameter (Front), in (mm) ............... 1.5748 (40.000)
Camshaft Journal Outer Diameter (Middle), in (mm) ............... 1.5354 (39.000)
Camshaft Journal Outer Diameter (Rear), in (mm) ............... 1.4961 (38.000)
Camshaft Bearing Oil Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Cam Lobe Height (Intake), in (mm) ............... 1.3413 (34.070)
Cam Lobe Height (Exhaust), in (mm) ............... 1.3413 (34.070)
Camshaft Axial End Play, in (mm) ............... 0.0020-0.0059 (0.050-0.150)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4724 (12.000)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.4732 (12.020)
Rocker Arm Bushing to Shaft Clearance, in (mm) ............... 0.0004-0.0020 (0.010-0.050)
Tappet Outer Diameter, in (mm) ............... 0.7874 (20.000)
Tappet to Cylinder Block Bore Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Crankshaft Timing Gear Backlash, in (mm) ............... 0.0012-0.0047 (0.030-0.120)
Camshaft Timing Gear Backlash, in (mm) ............... 0.0098 (0.250)
Idler Gear Shaft Outer Diameter, in (mm) ............... 1.1811 (30.000)
Idler Gear Bushing Inner Diameter, in (mm) ............... 1.1823 (30.030)
Idler Gear Bushing Oil Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)

Tightening Torques

Cylinder Head Bolts, lb-ft (Nm) ............... 54.2-57.9 (73.5-78.5)
Connecting Rod Cap Nuts, lb-ft (Nm) ............... 23.1-25.3 (31.4-34.3)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 36.2-39.8 (49.0-54.0)
Flywheel Fastening Bolts, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Crankshaft Pulley Center Bolt, lb-ft (Nm) ............... 72.3-79.6 (98.0-107.9)
Camshaft Thrust Plate Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Rocker Arm Shaft Support Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Cylinder Head Rocker Cover Nuts, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Timing Gear Case Cover Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pan Mounting Drain Plug, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Oil Pan Securing Perimeter Bolts, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Fuel Injection Nozzle Assembly Retention, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Fuel Injection Delivery Valve Holder, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Fuel High Pressure Line Flare Nuts, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Injection Pump Mounting Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Glow Plugs Installation Fastener, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Oil Pressure Switch Sensor Thread, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Coolant Temperature Sensor Assembly, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Water Pump Assembly Securing Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Exhaust Manifold Retention Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Intake Manifold Securing Hardware, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Starter Motor Mounting Flange Bolts, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Alternator Pivot and Tensioner Fasteners, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Idler Gear Shaft Plate Retaining Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Strainer Intake Tube Bracket Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Oil Pump Cover Plate Screws, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Fuel Leak Off Pipe Union Joint Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Flywheel Housing Adaptor Flange Bolts, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Front Gear Case Engine Block Joint Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Valve Clearance Adjusting Screw Locknuts, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Breather Assembly Mounting Screws, lb-ft (Nm) ............... 3.6-5.1 (4.9-6.9)
Fan Drive Pulley Assembly Retaining Nut, lb-ft (Nm) ............... 50.6-57.9 (68.6-78.5)
Thermostat Housing Cover Screws, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Injection Pump Automatic Timer Nut, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Governor Housing Cover Plate Fasteners, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Stop Lever Shaft Pin Nut, lb-ft (Nm) ............... 3.6-5.1 (4.9-6.9)
Fuel Feed Pump Block Mounting Nuts, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Oil Pressure Relief Valve Assembly Plug, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Main Bearing Cap Side Alignment Bolts, lb-ft (Nm) ............... 18.1-25.3 (24.5-34.3)
Rear Oil Seal Case Retaining Bolts, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)

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• Mitsubishi Engines Specs
  
• Mitsubishi K3E Specs
  
• Mitsubishi K3F Specs
  
• Mitsubishi K3H Specs
  
• Mitsubishi K3M Specs
  

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