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Komatsu 3D95S Engine

The Komatsu 3D95S (specifically within the 3D95S-W-1 layout) is a legacy, naturally aspirated 3-cylinder, in-line, 4-stroke diesel engine. Developed under Komatsu’s 95 Series platform, this water-cooled power unit is primarily built for high-reliability heavy applications, commonly found in mini-excavators like the Komatsu PC40-6, small agricultural tractors, and stationary diesel generator sets. The engine utilizes a heavy-duty cast iron block design, engineered to maximize structural rigidity while maintaining a compact footprint for small-scale industrial applications. Production has been discontinued, transitioning the unit entirely into an archived support and rebuild status.

Cylinder and Valve Configuration: 3-cylinder, inline, overhead valve (OHV) pushrod design. Total Valves: 6 valves total (1 intake valve and 1 exhaust valve per cylinder). Cylinder Bore: 95.0 mm. Piston Stroke: 95.0 mm. Total Displacement: 2.44 liters (2445 cc). Cooling System: Liquid-cooled, forced centrifugal water pump circulation. Circuit Control: Thermostatically controlled bypass circuit using a pellet-type thermostat to regulate optimal engine operating temperatures. Fan Drive: Belt-driven pusher or puller cooling fan configured directly via the crankshaft pulley hub.

Fuel System: Mechanical direct injection system utilizing a dedicated inline or distributor-type mechanical fuel injection pump. Fuel Delivery: High-pressure steel lines connected to mechanical multi-hole injection nozzles opening via pre-set spring pressure. Governor: Mechanical all-speed governor integrated into the injection pump housing to maintain stability across varying loads. Filtration: Primary fuel water separator paired with a secondary fine-particle spin-on fuel filter element. Lubrication System: Forced lubrication feed via a gear-driven oil pump. Filtration: Full-flow, spin-on cartridge oil filtration system paired with an internal bypass valve to ensure constant delivery during cold starts.

General Technical Data

Engine Specifications

Engine Model ............... Komatsu 3D95S-W-1
Engine Type ............... 4-cycle inline vertical direct injection liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line vertical
Engine Bore, mm (in) ............... 95.0 (3.74)
Engine Stroke, mm (in) ............... 95.0 (3.74)
Displacement, L (cu.in) ............... 2.445 (149.2)
Rated Engine Power, kW (hp) ............... 29.0-42.5 (39.0-57.0)
Rated Engine Speed, rpm ............... 2450-2600
Maximum Torque, Nm (lb-ft) ............... 150-155 (111-114) at 1300-2000 rpm
Low Idle Speed, rpm ............... 750-850
High Idle Speed, rpm ............... 2800-2950
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 17.0:1
Firing Order ............... 1-2-3
Valve Mechanism Type ............... Overhead valve pushrod driven design
Number of Valves per Cylinder ............... 2 (1 intake, 1 exhaust)
Camshaft Drive Method ............... Helical gear train driven from crankshaft
Direction of Rotation ............... Counterclockwise viewed from flywheel end
Cylinder Block Material ............... High-strength cast iron
Cylinder Head Material ............... Premium cast iron alloy
Cylinder Liner Type ............... Dry type thin-wall liner
Combustion Chamber ............... Direct injection direct bowl-in-piston type
Lubrication Method ............... Forced pressure feed by gear pump
Cooling Method ............... Forced circulation by centrifugal water pump
Air Cleaner Type ............... Dry type element with cyclone pre-cleaner
Starting System ............... Electric motor starter
Electrical System ............... 12V or 24V

Fuel System

Fuel Injection Pump Type ............... Bosch-M inline type pump mechanism
Fuel Feed Pump Type ............... Mechanical plunger type piston pump plunger driven
Governor Type ............... Mechanical all-speed governor centrifugal type
Injection Timing, deg ............... 12-14 BTDC
Fuel Injection Nozzle Type ............... Multi-hole nozzle type orifice design
Number of Nozzle Orifices ............... 4
Nozzle Orifice Diameter, mm (in) ............... 0.26 (0.0102)
Nozzle Valve Opening Pressure, kPa (psi) ............... 21574-22555 (3129-3271)
Nozzle Injection Pressure Std, kPa (psi) ............... 22065 (3200)
Fuel Filter Type ............... Spin-on full flow cartridge type paper element
Fuel Filter Water Separator ............... Integrated transparent sedimenter bowl
Maximum Fuel Transfer Pump Pressure, kPa (psi) ............... 196 (28.4)
Fuel Return Line Maximum Back Pressure, kPa (psi) ............... 20 (2.9)
Injection Pipe Inner Diameter, mm (in) ............... 2.0 (0.078)
Injection Pipe Outer Diameter, mm (in) ............... 6.0 (0.236)
Maximum Overflow Valve Cracking Pressure, kPa (psi) ............... 157 (22.8)
Fuel Tank Recommended Venting Pressure, kPa (psi) ............... 4.9 (0.71)
Fuel Prime Pump Type ............... Manual hand priming plunger pump mechanism
Recommended Fuel Grade ............... ASTM D975 No. 2-D ultra-low sulfur diesel

Dimensions and Weight

Overall Length, mm (in) ............... 625 (24.6)
Overall Width, mm (in) ............... 530 (20.8)
Overall Height, mm (in) ............... 750 (29.5)
Dry Weight, kg (lbs) ............... 215 (474)
Wet Weight, kg (lbs) ............... 230 (507)

Maintenance Data

Service Information

Compression Pressure, kPa (psi) ............... 2942 (426.7)
Minimum Compression Pressure, kPa (psi) ............... 2452 (355.6)
Max Pressure Difference Between Cylinders, kPa (psi) ............... 294 (42.6)
Oil Pressure at Rated Speed, kPa (psi) ............... 294-441 (42.6-64.0)
Oil Pressure at Idle Speed, kPa (psi) ............... 78 (11.3)
Standard Oil Temperature, C (F) ............... 90-105 (194-221)
Standard Coolant Temperature, C (F) ............... 80-90 (176-194)
Thermostat Initial Opening Temperature, C (F) ............... 76.5 (170)
Thermostat Full Open Temperature, C (F) ............... 90 (194)
Radiator Cap Pressure, kPa (psi) ............... 49-68 (7.1-9.9)
Drive Belt Deflection (Used Belt), mm (in) ............... 11.0-14.0 (0.43-0.55)
Intake Valve Clearance, Cold, mm (in) ............... 0.35 (0.014)
Exhaust Valve Clearance, Cold, mm (in) ............... 0.50 (0.020)

Engine Oil and Coolant

Engine Oil Type .................. SAE 5W-30, SAE 15W-40, SAE 10W-30
API Service Classifications ......................... CH-4 or CI-4
Engine Oil Capacity (Maximum Level), L (qt) ............... 7.0 (7.4)
Engine Oil Capacity (Minimum Level), L (qt) ............... 5.0 (5.3)
Engine Oil Capacity with Filter, L (qt) ............... 7.8 (8.2)
Cooling System Capacity (Engine Only), L (qt) ............... 4.5 (4.8)

Service Intervals

Change oil and filter ............... Every 250 hours
Inspect air cleaner ............... Every 100 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 1000 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 2000 hours
Compression test ............... Every 1000 hours
Clean radiator core ............... Every 250 hours
Inspect belt tension ............... Every 150 hours

Service Specifications

Cylinder Bore Inner Diameter, mm (in) ............... 95.000-95.030 (3.7402-3.7413)
Cylinder Bore Max Wear Limit, mm (in) ............... 95.200 (3.7480)
Cylinder Bore Out of Roundness, mm (in) ............... 0.020 (0.0008)
Connecting Rod Small End Bushing I.D, mm (in) ............... 30.020-30.035 (1.1819-1.1825)
Crankshaft Main Journal Diameter, mm (in) ............... 70.000-70.015 (2.7559-2.7565)
Crankpin Journal Diameter, mm (in) ............... 57.000-57.015 (2.2441-2.2447)
Crankshaft Main Bearing Clearance, mm (in) ............... 0.040-0.090 (0.0016-0.0035)
Connecting Rod Bearing Clearance, mm (in) ............... 0.035-0.085 (0.0014-0.0033)
Crankshaft End Play, mm (in) ............... 0.070-0.220 (0.0028-0.0087)
Thrust Washer Thickness, mm (in) ............... 2.420-2.470 (0.0953-0.0972)
Connecting Rod Side Axial Play, mm (in) ............... 0.100-0.250 (0.0039-0.0098)
Piston Skirt Outer Diameter, mm (in) ............... 94.840-94.870 (3.7339-3.7350)
Piston to Cylinder Liner Clearance, mm (in) ............... 0.130-0.190 (0.0051-0.0075)
Piston Pin Bore Inner Diameter, mm (in) ............... 30.006-30.015 (1.1813-1.1817)
Piston Pin Outer Diameter, mm (in) ............... 29.994-30.000 (1.1809-1.1811)
Piston Pin to Piston Pin Bore Clearance, mm (in) ............... 0.006-0.021 (0.0002-0.0008)
Piston Pin to Con Rod Bushing Clearance, mm (in) ............... 0.020-0.041 (0.0008-0.0016)
Top Ring Groove Width, mm (in) ............... 2.560-2.580 (0.1008-0.1016)
Second Ring Groove Width, mm (in) ............... 2.030-2.050 (0.0799-0.0807)
Oil Ring Groove Width, mm (in) ............... 4.020-4.040 (0.1583-0.1591)
Top Ring Side Clearance, mm (in) ............... 0.060-0.095 (0.0024-0.0037)
Second Ring Side Clearance, mm (in) ............... 0.050-0.085 (0.0020-0.0033)
Oil Ring Side Clearance, mm (in) ............... 0.030-0.065 (0.0012-0.0026)
Top Ring End Gap, mm (in) ............... 0.250-0.400 (0.0098-0.0157)
Second Ring End Gap, mm (in) ............... 0.300-0.450 (0.0118-0.0177)
Oil Piston End Gap, mm (in) ............... 0.250-0.450 (0.0098-0.0177)
Cylinder Head Surface Distortion Flatness, mm (in) ............... 0.050 (0.0020)
Cylinder Block Upper Surface Distortion Flatness, mm (in) ............... 0.050 (0.0020)
Intake Valve Stem Outer Diameter, mm (in) ............... 7.960-7.975 (0.3134-0.3140)
Intake Valve Guide Inner Diameter, mm (in) ............... 8.010-8.025 (0.3154-0.3159)
Intake Valve Guide to Stem Clearance, mm (in) ............... 0.035-0.065 (0.0014-0.0026)
Exhaust Valve Stem Outer Diameter, mm (in) ............... 7.945-7.960 (0.3128-0.3134)
Exhaust Valve Guide Inner Diameter, mm (in) ............... 8.010-8.025 (0.3154-0.3159)
Exhaust Valve Guide to Stem Clearance, mm (in) ............... 0.050-0.080 (0.0020-0.0031)
Valve Seat Angle, deg ............... 45
Valve Head Margin Thickness, mm (in) ............... 1.400-1.600 (0.0551-0.0630)
Valve Spring Free Length, mm (in) ............... 49.200 (1.9370)
Camshaft Journal Outer Diameter (Front), mm (in) ............... 50.910-50.930 (2.0043-2.0051)
Camshaft Journal Outer Diameter (Center), mm (in) ............... 50.660-50.680 (1.9945-1.9953)
Camshaft Journal Outer Diameter (Rear), mm (in) ............... 50.410-50.430 (1.9846-1.9854)
Camshaft Bushing Inner Diameter (Front), mm (in) ............... 51.000-51.030 (2.0079-2.0091)
Camshaft Journal Clearance, mm (in) ............... 0.070-0.120 (0.0028-0.0047)
Camshaft End Play, mm (in) ............... 0.050-0.180 (0.0020-0.0071)
Cam Lobe Height (Intake), mm (in) ............... 42.030-42.080 (1.6547-1.6567)
Cam Lobe Height (Exhaust), mm (in) ............... 42.060-42.110 (1.6559-1.6579)
Rocker Arm Shaft Outer Diameter, mm (in) ............... 19.970-19.990 (0.7862-0.7870)
Rocker Arm Bushing Inner Diameter, mm (in) ............... 20.000-20.020 (0.7874-0.7882)
Rocker Arm Bushing to Shaft Clearance, mm (in) ............... 0.010-0.050 (0.0004-0.0020)
Tappet Lifter Journal Outer Diameter, mm (in) ............... 23.960-23.980 (0.9433-0.9441)
Tappet Guide Hole Inner Diameter, mm (in) ............... 24.000-24.020 (0.9449-0.9457)
Tappet Lifter to Guide Hole Clearance, mm (in) ............... 0.020-0.060 (0.0008-0.0024)
Timing Gear Backlash (Crank to Cam), mm (in) ............... 0.080-0.180 (0.0031-0.0071)
Timing Gear Backlash (Cam to Injection Pump), mm (in) ............... 0.080-0.180 (0.0031-0.0071)

Tightening Torques

Cylinder Head Bolts (1-Step), Nm (lb-ft) ............... 69 (51)
Cylinder Head Bolts (2-Step), Nm (lb-ft) ............... 108 (80)
Main Bearing Cap Bolts (1-Step), Nm (lb-ft) ............... 114 (84)
Main Bearing Cap Bolts (2-Step), Nm (lb-ft) ............... 133 (98)
Connecting Rod Cap Nut, Nm (lb-ft) ............... 39-41 (29-30)
Flywheel Retaining Bolts, Nm (lb-ft) ............... 127-137 (94-101)
Crankshaft Damper Pulley Nut, Nm (lb-ft) ............... 196-216 (145-159)
Camshaft Thrust Plate Bolt, Nm (lb-ft) ............... 22-26 (16-19)
Camshaft Gear Bolt, Nm (lb-ft) ............... 78-88 (58-65)
Rocker Arm Shaft Bracket Bolt, Nm (lb-ft) ............... 34-40 (25-30)
Valve Clearance Adjusting Screw, Nm (lb-ft) ............... 18-22 (13-16)
Cylinder Head Valve Cover Sealing Nut, Nm (lb-ft) ............... 8-12 (6-9)
Oil Pan Drain Plug, Nm (lb-ft) ............... 69-78 (51-58)
Oil Pan Mounting Perimeter Bolts, Nm (lb-ft) ............... 20-24 (15-18)
Timing Gear Case Cover Mounting Bolts, Nm (lb-ft) ............... 20-24 (15-18)
Flywheel Housing Core Mounting Bolts, Nm (lb-ft) ............... 78-88 (58-65)
Fuel Injection Pump Drive Gear Nut, Nm (lb-ft) ............... 59-69 (44-51)
Fuel Injection Pump Holding Base Nut, Nm (lb-ft) ............... 20-24 (15-18)
Fuel Injector Assembly Retention Bolt, Nm (lb-ft) ............... 44-49 (33-36)
Fuel Injection High Pressure Line Nut, Nm (lb-ft) ............... 25-29 (18-21)
Fuel Return Line Banjo Fitting Bolt, Nm (lb-ft) ............... 10-14 (7-10)
Water Pump Assembly Housing Mounting Bolt, Nm (lb-ft) ............... 20-24 (15-18)
Thermostat Housing Cap Bolts, Nm (lb-ft) ............... 20-24 (15-18)
Exhaust Manifold Retention Stud Nuts, Nm (lb-ft) ............... 25-29 (18-21)
Intake Manifold Core Retention Bolts, Nm (lb-ft) ............... 20-24 (15-18)
Starter Motor Mounting Flange Bolts, Nm (lb-ft) ............... 78-88 (58-65)
Alternator Pivoting Support Flange Bolt, Nm (lb-ft) ............... 44-54 (33-40)
Oil Pump Assembly Internal Backing Screw, Nm (lb-ft) ............... 25-30 (18-22)
Oil Pressure Regulator Valve Relief Plug, Nm (lb-ft) ............... 39-49 (29-36)
Oil Cooler Core Assembly Nuts, Nm (lb-ft) ............... 20-24 (15-18)
Glow Plug Installation Body, Nm (lb-ft) ............... 15-20 (11-15)

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