________________________________________________________________________________

Mitsubishi K3B Engine

The Mitsubishi K3B is a compact, vertical, water-cooled, 4-stroke, 3-cylinder inline diesel engine. Engineered by Mitsubishi Heavy Industries, this engine is widely recognized for its high power-to-weight ratio, reliability, and compact design. It is heavily utilized across global agricultural, light construction, and industrial markets. It commonly serves as the primary powerplant for mini-excavators (such as the Hanix N150-2) and compact utility tractors, including the Iseki TU1400 and TX1510 models.

The cylinder head utilizes an overhead valve (OHV) configuration driven by a conventional camshaft and pushrod arrangement. The engine features 2 valves per cylinder, equating to a total of 3 intake valves and 3 exhaust valves across the entire block. Valve clearance adjustments are maintained mechanically through rocker arm adjusting screws. Bore Diameter: 68 mm (2.68 inches). Stroke Length: 78 mm (3.07 inches). Total Displacement: 0.849 Liters (849 cc / 51.8 cubic inches). Compression Ratio: 23:1.

Fuel System: Fuel delivery relies on an indirect injection (IDI) design paired with an efficiency-focused swirl combustion chamber layout. Pressurized injection is controlled via a dedicated Bosch M-type in-line injection pump synchronizing delivery to individual throttle-type fuel injection nozzles. Speed management and throttle response are regulated mechanically via a built-in centrifugal flyweight governor. A primary fuel filter assembly with integrated water separation protects the injection components.

Lubrication System: Engine lubrication uses a fully pressurized, forced lubrication system driven by a high-precision trochoid oil pump. Oil is pumped under pressure through main galleries to supply the crankshaft bearings, connecting rod journals, and rocker assemblies. System protection is provided by a full-flow, replaceable spin-on paper element oil filter along with an integrated oil pressure warning switch.

Cooling System: Thermal regulation is managed by a closed, high-capacity liquid-cooled system. Coolant circulation is forced through the block and cylinder head passages via a belt-driven centrifugal water pump. The design includes an external radiator, a cooling fan, and a mechanical wax-pellet thermostat to govern flow and safely maintain optimal operational temperatures.

General Technical Data

Engine Specifications

Engine Model ............... Mitsubishi K3B
Engine Type ............... 4-cycle inline 3-cylinder swirl-chamber liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 2.677 (68.0)
Engine Stroke, in (mm) ............... 3.071 (78.0)
Displacement, cu.in (cc) ............... 51.85 (849)
Rated Engine Power, hp (kW) ............... 17.0 (12.5)
Rated Engine Speed, rpm ............... 2600-2800
Max No-Load Speed, rpm ............... 2950-3050
Idle Speed, rpm ............... 800-900
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 23.0:1
Firing Order ............... 1-3-2
Direction of Rotation ............... Counterclockwise viewed from flywheel side
Cylinder Block Material ............... Cast iron
Cylinder Head Material ............... Cast iron
Lubrication System ............... Forced pressure circulation
Oil Pump Type ............... Trochoid gear pump
Oil Filter Type ............... Full-flow spin-on cartridge
Cooling System ............... Forced liquid circulation
Water Pump Type ............... Belt-driven centrifugal impeller
Cooling Fan Type ............... Suction or pusher plastic fan
Air Cleaner Type ............... Dry element element with cyclonic pre-cleaner
Glow Plug Type ............... Sheathed rapid heating wire
Starting System ............... Electric starter motor
Electrical System ............... 12V

Fuel System

Fuel Injection Pump Type ............... Bosch M type mini inline pump
Fuel Injection Nozzle Type ............... Throttle nozzle type
Fuel Injection Timing, deg BTDC ............... 21.0-23.0
Injection Pump Injection Pressure, psi (bar) ............... 1706.8 (118.0)
Fuel Transfer Pump Type ............... Mechanical diaphragm type
Fuel Filter Type ............... Cartridge element with integrated water sedimenter
Governor Type ............... Centrifugal flyweight mechanical governor
Fuel Injection Nozzle Opening Pressure, psi (bar) ............... 1707-1849 (118-128)
Fuel Line Outer Diameter, in (mm) ............... 0.187 (4.76)
Fuel Return Line Outer Diameter, in (mm) ............... 0.236 (6.0)
Maximum Fuel System Delivery Pressure, psi (bar) ............... 28.4 (1.96)
Fuel Tank Venting System ............... Atmospheric open type breather
Fuel Injection Pipe Wall Thickness, in (mm) ............... 0.059 (1.5)
Nozzle Holder Gasket Thickness, in (mm) ............... 0.039 (1.0)
Fuel Leak-off Line Internal Diameter, in (mm) ............... 0.118 (3.0)

Dimensions and Weight

Overall Engine Length, in (mm) ............... 19.9 (505)
Overall Engine Width, in (mm) ............... 17.5 (445)
Overall Engine Height, in (mm) ............... 21.6 (550)
Dry Engine Weight, lbs (kg) ............... 203 (92)

Maintenance Data

Service Information

Compression Pressure, Standard, psi (bar) ............... 426.7 (29.4)
Compression Pressure, Limit, psi (bar) ............... 341.3 (23.5)
Compression Variance Between Cylinders, psi (bar) ............... 35.5 (2.45)
Oil Pressure at Rated Speed, psi (bar) ............... 42.6-56.8 (2.94-3.92)
Oil Pressure at Idle Speed, psi (bar) ............... 14.2 (0.98)
Thermostat Opening Temperature, F (C) ............... 169-176 (76.5-80.0)
Thermostat Full Open Temperature, F (C) ............... 194 (90.0)
Radiator Cap Pressure, psi (bar) ............... 12.8 (0.88)
Fan Belt Deflection (Under 22 lb Force), in (mm) ............... 0.39-0.47 (10.0-12.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.0098 (0.250)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.0098 (0.250)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30W, SAE 10W-30, or 15W-40
API Service Classifications ......................... CD, CE, CF-4
Engine Oil Capacity, Upper Limit, qt (L) ............... 3.17 (3.0)
Engine Oil Capacity, Lower Limit, qt (L) ............... 1.90 (1.8)
Engine Coolant Capacity, qt (L) ............... 4.23 (4.0)

Service Intervals

Change oil and filter ............... Every 200 hours
Inspect air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 200 hours
Valve clearance adjustment ............... Every 400 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 800 hours
Clean radiator core ............... Every 250 hours
Inspect belt tension ............... Every 250 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 2.6771-2.6783 (68.000-68.030)
Cylinder Bore Inside Diameter, Wear Limit, in (mm) ............... 2.6850 (68.200)
Cylinder Bore Roundness, in (mm) ............... 0.0004 (0.010)
Cylinder Bore Taper, Wear Limit, in (mm) ............... 0.0059 (0.150)
Crankshaft Main Journal Diameter, in (mm) ............... 1.9673-1.9681 (49.970-49.990)
Crankshaft Main Bearing-to-Journal Clearance, in (mm) ............... 0.0014-0.0035 (0.035-0.090)
Crankshaft End Play, in (mm) ............... 0.0020-0.0079 (0.050-0.200)
Crankpin Journal Diameter, in (mm) ............... 1.7705-1.7713 (44.970-44.990)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.7876-0.7883 (20.006-0.024)
Connecting Rod Big End Journal I.D, in (mm) ............... 1.8898-1.8906 (48.000-48.020)
Connecting Rod Bearing-to-Crankpin Clearance, in (mm) ............... 0.0014-0.0033 (0.035-0.085)
Connecting Rod Side Play, in (mm) ............... 0.0039-0.0098 (0.100-0.250)
Thrust Washer Thickness, in (mm) ............... 0.0787-0.0807 (2.000-2.050)
Piston Skirt Outer Diameter, in (mm) ............... 2.6748-2.6760 (67.940-67.970)
Piston-to-Cylinder Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.7874-0.7877 (20.000-20.009)
Piston Pin Outer Diameter, in (mm) ............... 0.7871-0.7874 (19.993-20.000)
Piston Pin-to-Piston Pin Bore Clearance, in (mm) ............... 0.0000-0.0006 (0.000-0.016)
Piston Pin-to-Small End Bushing Clearance, in (mm) ............... 0.0002-0.0012 (0.006-0.031)
Top Ring Side Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Second Ring Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Oil Ring Side Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Top Ring End Gap, in (mm) ............... 0.0059-0.0137 (0.150-0.350)
Second Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Cylinder Head Surface Distortion Flatness, in (mm) ............... 0.0020 (0.050)
Cylinder Block Surface Distortion Flatness, in (mm) ............... 0.0020 (0.050)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2736-0.2742 (6.950-6.965)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2728-0.2736 (6.930-6.950)
Intake Valve Stem-to-Guide Clearance, in (mm) ............... 0.0014-0.0026 (0.035-0.065)
Exhaust Valve Stem-to-Guide Clearance, in (mm) ............... 0.0020-0.0033 (0.050-0.085)
Valve Guide Inside Diameter, in (mm) ............... 0.2756-0.2762 (7.000-7.015)
Valve Seat Angle, deg ............... 45
Valve Face Angle, deg ............... 45
Valve Margin Thickness, in (mm) ............... 0.0394 (1.000)
Valve Spring Free Length, in (mm) ............... 1.4803 (37.600)
Camshaft Journal Diameter (№1), in (mm) ............... 1.5732-1.5740 (39.960-39.980)
Camshaft Journal Diameter (№2), in (mm) ............... 1.5339-1.5346 (38.960-38.980)
Camshaft Journal Diameter (№3), in (mm) ............... 1.4945-1.4953 (37.960-37.980)
Camshaft Bearing-to-Journal Clearance, in (mm) ............... 0.0020-0.0043 (0.050-0.110)
Camshaft End Play, in (mm) ............... 0.0020-0.0098 (0.050-0.250)
Cam Lobe Height (Intake), in (mm) ............... 1.3213-1.3228 (33.560-33.600)
Cam Lobe Height (Exhaust), in (mm) ............... 1.3213-1.3228 (33.560-33.600)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4717-0.4724 (11.982-12.000)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.4732-0.4740 (12.020-12.040)
Rocker Arm-to-Shaft Clearance, in (mm) ............... 0.0008-0.0023 (0.020-0.058)
Tappet Outer Diameter, in (mm) ............... 0.7854-0.7862 (19.950-19.970)
Idler Gear Bushing Inside Diameter, in (mm) ............... 0.7874-0.7883 (20.000-20.021)
Idler Gear Shaft Outer Diameter, in (mm) ............... 0.7858-0.7869 (19.959-19.980)
Idler Gear Bushing-to-Shaft Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.062)

Tightening Torques

Cylinder Head Bolts (M12), lb-ft (Nm) ............... 79.5-86.8 (108.0-118.0)
Cylinder Head Bolts (M10), lb-ft (Nm) ............... 50.6-57.9 (69.0-78.0)
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 Mounting Bolts, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Crankshaft Pulley Center Bolt, lb-ft (Nm) ............... 72.3-79.6 (98.0-108.0)
Rocker Arm Shaft Bracket Bolts, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Cylinder Head Cover Acorn Nuts, lb-ft (Nm) ............... 4.3-5.8 (6.0-8.0)
Fuel Injection Nozzle Holder Assembly, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Fuel Injection Pipe Flare Nuts, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Injection Pump Delivery Valve Holder, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Glow Plugs Terminal Nut, lb-ft (Nm) ............... 1.1-1.4 (1.5-2.0)
Glow Plugs Body into Cylinder Head, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pan Drain Plug, lb-ft (Nm) ............... 25.3-32.5 (34.3-44.1)
Oil Pressure Switch Sensor Body, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Water Temperature Sensor Body, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Timing Gear Case Cover Fasteners (M6), lb-ft (Nm) ............... 5.8-7.2 (8.0-10.0)
Timing Gear Case Cover Fasteners (M8), lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Intake Manifold Securing Bolts, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Exhaust Manifold Securing Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Starter Motor Mounting Bolts, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Alternator Mounting Pivot Bolt, lb-ft (Nm) ............... 21.7-25.3 (29.4-34.3)
Oil Pump Cover Plate Screws, lb-ft (Nm) ............... 5.1-7.2 (7.0-10.0)
Flywheel Housing-to-Block Fasteners, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)

________________________________________________________________________________________

• Mitsubishi Engines Specs
  
• Mitsubishi K3A Specs
  
• Mitsubishi K3C Specs
  
• Mitsubishi K3D Specs
  
• Mitsubishi KE70 Specs
  
• Mitsubishi KE75 Specs
  

________________________________________________________________________________

________________________________________________________________________________________

_______________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________