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Mitsubishi K3A Engine

The Mitsubishi K3A is an industrial-grade, 3-cylinder, 4-cycle, water-cooled, vertical diesel engine designed for high durability and compact power applications. It utilizes an overhead valve (OHV) configuration and features a swirl combustion chamber with a high compression ratio. This makes it highly efficient for agricultural machinery, such as the Mitsubishi MT160 tractor, and various small industrial applications.

Valve Configuration: Overhead Valve (OHV) arrangement driven by a gear-linked camshaft. Cylinder layout: 3 cylinders in-line, operating with a firing order of 1-3-2. Cylinder bore: 65 mm (2.56 inches). Piston stroke: 78 mm (3.07 inches). Total displacement: 776 cc (47.4 cubic inches). Compression ratio: 23:1.

Fuel System : High-pressure Bosch M-type inline injection pump unit. Feed pump: Main line supplied by an electromagnetic fuel pump. Injection nozzles: Throttle-type injection nozzles coupled with a swirl combustion chamber layout. Governor assembly: Mechanical centrifugal flyweight type governor controlling fuel delivery curves across the RPM range. Filtration assembly: Dedicated primary paper-element fuel filter.

Lubrication System: Forced pressure lubrication loop. Oil pump assembly: Internal trochoid type pump driven by the engine gear train. Filtration: Replaceable full-flow paper element filter cartridge. Monitoring: Integrated oil pressure switch to monitor critical line pressure drop. Cooling System: Liquid-cooled forced-circulation design via an engine-driven water pump.

General Technical Data

Engine Specifications

Engine Model ............... Mitsubishi K3A
Engine Type ............... 4-cycle inline 3-cylinder liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line
Combustion Chamber ............... Swirl combustion chamber with preheater
Valve Mechanism ............... Overhead valve (OHV)
Engine Bore, in (mm) ............... 2.56 (65.0)
Engine Stroke, in (mm) ............... 3.07 (78.0)
Displacement, cu.in (L) ............... 46.7-47.4 (0.766-0.776)
Gross Engine Power, hp (kW) ............... 12.8-16.5 (9.5-12.3)
Rated Engine Speed, rpm ............... 2500-2700
Peak Torque ............... 33.3-34.7 lb-ft (45.2-47.1 Nm) at 1800-1900 rpm
Low Idle Speed, rpm ............... 700-800
High Idle Speed, rpm ............... 2800-2950
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 23.0:1
Firing Order ............... 1-3-2
Cylinder Block Type ............... Monoblock cast iron non-liner design
Cylinder Head Type ............... Cast iron single piece crossflow design
Lubrication System ............... Full-pressure trochoid pump circulation
Oil Pump Type ............... Trochoid gear driven from crankshaft
Oil Filter Type ............... Full-flow spin-on cartridge elements
Cooling System ............... Forced liquid circulation with centrifugal pump
Water Pump Type ............... Belt-driven centrifugal impeller
Air Cleaner Type ............... Dry single or dual element corrugated paper
Starting System ............... Electric motor starter engagement
Electrical System Voltage, V ............... 12

Fuel System

Injection Pump Type ............... Bosch-M inline type or ND-PFR mini pump
Fuel Feed Pump Type ............... Mechanical diaphragm, driven by camshaft
Fuel Injection Nozzle Type ............... Throttle type or pintle type micro orifice nozzles
Injection Pressure, psi (kg/cm2) ............... 1707.0-1849.0 (120.0-130.0)
Injection Nozzle Opening Limit, psi (kg/cm2) ............... 1565.0 (110.0)
Injection Timing, deg BTDC ............... 19.0-21.0
Governor Type ............... Mechanical all-speed centrifugal ball type
Fuel Filter Element Type ............... Spin-on element with water sedimenter
Fuel Consumption Rate at Full Load, g/hp-h (g/kW-h) ............... 186.0 (250.0)
Fuel Delivery Line Internal Diameter, in (mm) ............... 0.078 (2.0)
Fuel Delivery Line Outer Diameter, in (mm) ............... 0.236 (6.0)
Fuel Return Line Outer Diameter, in (mm) ............... 0.196 (5.0)
Injection Pump Plunge Diameter, in (mm) ............... 0.196 (5.0)
Injection Pump Plunger Stroke, in (mm) ............... 0.275 (7.0)
Nozzle Valve Diameter, in (mm) ............... 0.157 (4.0)
Nozzle Valve Lift, in (mm) ............... 0.013 (0.35)
Fuel Feed Pump Pressure, psi (kg/cm2) ............... 2.84-4.26 (0.20-0.30)
Recommended Fuel Grade ............... ASTM Number 2-D ultra-low sulfur diesel fuel

Dimensions and Weight

Overall Length, in (mm) ............... 18.5 (470)
Overall Width, in (mm) ............... 16.9 (430)
Overall Height, in (mm) ............... 20.5 (520)
Dry Weight, lbs (kg) ............... 176-200 (80-91)
Wet Weight, lbs (kg) ............... 194-216 (88-98)

Maintenance Data

Service Information

Compression Pressure at 280 rpm, psi (kg/cm2) ............... 455.1 (32.0)
Minimum Compression Limit, psi (kg/cm2) ............... 370.0 (26.0)
Oil Pressure at 2700 rpm, psi (kg/cm2) ............... 42.6-56.8 (3.0-4.0)
Oil Pressure at Idle Speed, psi (kg/cm2) ............... 14.2 (1.0)
Radiator Pressure Cap, psi (kg/cm2) ............... 12.8 (0.9)
Coolant Thermostat Opening Temperature, F (C) ............... 160.0 (71.0)
Coolant Thermostat Full Open Temperature, F (C) ............... 185.0 (85.0)
V-Belt Tension Deflection, in (mm) ............... 0.275-0.393 (7.0-10.0)
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, CE, CF-4
Engine Oil Capacity, Full Sump, qt (L) ............... 3.17 (3.0)
Engine Oil Capacity, Low Mark, qt (L) ............... 2.11 (2.0)
Cooling System Capacity, qt (L) ............... 5.28 (5.0)

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) ............... 2.5590-2.5598 (65.000-65.020)
Cylinder Bore Inside Diameter, Wear Limit, in (mm) ............... 2.5669 (65.200)
Cylinder Bore Maximum Out-of-Round, in (mm) ............... 0.0007 (0.020)
Crankshaft Main Journal Outer Diameter, in (mm) ............... 1.9681-1.9685 (49.990-50.000)
Crankshaft Main Journal Outer Diameter, Wear Limit, in (mm) ............... 1.9566 (49.700)
Crankshaft Main Journal Oil Clearance, in (mm) ............... 0.0011-0.0027 (0.030-0.070)
Crankpin Journal Outer Diameter, in (mm) ............... 1.5744-1.5748 (39.990-40.000)
Crankpin Journal Oil Clearance, in (mm) ............... 0.0011-0.0025 (0.030-0.065)
Crankshaft Axial End Play, in (mm) ............... 0.0019-0.0070 (0.050-0.180)
Connecting Rod Big End Side Play, in (mm) ............... 0.0039-0.0098 (0.100-0.250)
Piston Skirt Outer Diameter, in (mm) ............... 2.5563-2.5571 (64.930-64.950)
Piston-to-Cylinder Running Clearance, in (mm) ............... 0.0023-0.0035 (0.060-0.090)
Piston Pin Outer Diameter, in (mm) ............... 0.7871-0.7874 (19.992-20.000)
Piston Pin-to-Piston Bore Clearance, in (mm) ............... 0.00007-0.00047 (0.002-0.012)
Piston Pin-to-Con Rod Small End Bushing Clearance, in (mm) ............... 0.0003-0.0009 (0.008-0.025)
Top Ring Groove Width, in (mm) ............... 0.0807-0.0815 (2.050-2.070)
Second Ring Groove Width, in (mm) ............... 0.0807-0.0815 (2.050-2.070)
Oil Ring Groove Width, in (mm) ............... 0.1582-0.1590 (4.020-4.040)
Top Ring Side Clearance, in (mm) ............... 0.0027-0.0043 (0.070-0.110)
Second Ring Side Clearanced, in (mm) ............... 0.0015-0.0031 (0.040-0.080)
Oil Ring Side Clearance, in (mm) ............... 0.0011-0.0027 (0.030-0.070)
Top Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Second Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0157 (0.200-0.400)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.2736-0.2742 (6.950-6.965)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.2728-0.2736 (6.930-6.950)
Intake Valve Stem-to-Guide Clearance, in (mm) ............... 0.0013-0.0027 (0.035-0.070)
Exhaust Valve Stem-to-Guide Clearance, in (mm) ............... 0.0019-0.0033 (0.050-0.085)
Valve Guide Tube Bore Inside Diameter, in (mm) ............... 0.2755-0.2762 (7.000-7.018)
Intake Valve Guide Outer Diameter, in (mm) ............... 1.181 (30.0)
Exhaust Valve Guide Outer Diameter, in (mm) ............... 1.023 (26.0)
Valve Face Seating Angle, deg ............... 45.0
Intake Valve Seat Contact Width, in (mm) ............... 0.047-0.059 (1.2-1.5)
Exhaust Valve Seat Contact Width, in (mm) ............... 0.047-0.059 (1.2-1.5)
Valve Guide Tube Total Length, in (mm) ............... 1.653 (42.0)
Valve Spring Free Length, in (mm) ............... 1.496 (38.0)
Camshaft Bearing Outside Diameter (Front), in (mm) ............... 1.4937-1.4944 (37.940-37.960)
Camshaft Bearing Outside Diameter (Center), in (mm) ............... 1.4543-1.4551 (36.940-36.960)
Camshaft Bearing Outside Diameter (Rear), in (mm) ............... 1.4149-1.4157 (35.940-35.960)
Camshaft Journal-to-Block Bushing Clearance, in (mm) ............... 0.0015-0.0035 (0.040-0.090)
Camshaft End Play, in (mm) ............... 0.0019-0.0059 (0.050-0.150)
Cam Lobe Height (Intake), in (mm) ............... 1.2952 (32.90)
Cam Lobe Height (Exhaust), in (mm) ............... 1.2952 (32.90)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4724 (12.0)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.4735 (12.03)
Rocker Arm Shaft-to-Bushing Clearance, in (mm) ............... 0.0004-0.0027 (0.010-0.070)
Idler Gear Bushing-to-Shaft Clearance, in (mm) ............... 0.0007-0.0027 (0.020-0.070)

Tightening Torques

Cylinder Head M12 Bolts (Stage 1), lb-ft (Nm) ............... 28.9-36.1 (40.0-50.0)
Cylinder Head M12 Bolts (Stage 2), lb-ft (Nm) ............... 57.8-65.0 (80.0-90.0)
Cylinder Head M12 Bolts (Stage 3), lb-ft (Nm) ............... 79.5-86.8 (107.8-117.6)
Cylinder Head M10 Bolts (Stage 1), lb-ft (Nm) ............... 21.6-28.9 (30.0-40.0)
Cylinder Head M10 Bolts (Stage 2), lb-ft (Nm) ............... 50.6-57.9 (68.6-78.4)
Connecting Rod Cap Nuts, lb-ft (Nm) ............... 23.1-25.3 (31.3-34.3)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 36.2-39.8 (49.0-53.9)
Flywheel Retaining Bolts, lb-ft (Nm) ............... 57.8-65.0 (78.4-88.2)
Crankshaft Front Pulley Center Nut, lb-ft (Nm) ............... 72.3-86.8 (98.0-117.6)
Rocker Arm Shaft Support Bracket Bolts, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Rocker Arm Adjusting Screw Locknuts, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Cylinder Head Valve Cover Cap Nuts, lb-ft (Nm) ............... 3.6-5.7 (4.9-7.8)
Injection Pump Assembly Mounting Nuts, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Injection Nozzle Assembly Retaining Clamp Bolt, lb-ft (Nm) ............... 36.2-43.3 (49.0-58.8)
Fuel High Pressure Line Union Delivery Nuts, lb-ft (Nm) ............... 18.0-25.3 (24.5-34.3)
Fuel Injection Nozzle Holder Mating Cap Nut, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Glow Plug Body Core, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Glow Plug Electrical Wiring Terminal Nut, lb-ft (Nm) ............... 0.7-1.4 (1.0-2.0)
Exhaust Manifold Mounting Stud Flange Nuts, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Intake Manifold Mounting Bolts, lb-ft (Nm) ............... 10.8-18.0 (14.7-24.5)
Oil Sump Base Drain Plug Hex Fitting Bolt, lb-ft (Nm) ............... 28.9-39.8 (39.2-53.9)
Oil Sump Pan Perimeter Flange Mounting Bolts, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Oil Pressure Sensor Assembly Unit, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Water Pump Assembly Body Housing Fasteners, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Coolant Temperature Sensor Unit, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Thermostat Housing Assembly Clamp Cap Bolts, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Starter Motor Housing Mounting Flange Bolts, lb-ft (Nm) ............... 28.9-39.8 (39.2-53.9)
Alternator Pivoting Adjusting Bracket Lock Bolts, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Alternator Main Support Swivel Hinge Pivot Bolt, lb-ft (Nm) ............... 28.9-39.8 (39.2-53.9)
Timing Gear Case Cover Housing Front Bolts, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)
Idler Gear Support Shaft Center Spindle Mount Bolt, lb-ft (Nm) ............... 28.9-39.8 (39.2-53.9)
Camshaft Thrust Stopping Plate Flange Bolts, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Oil Pump Back Cover Fastener, lb-ft (Nm) ............... 3.6-5.7 (4.9-7.8)
Oil Filter Assembly Core, lb-ft (Nm) ............... 14.4-21.6 (19.6-29.4)

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

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