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Komatsu 3D88E Engine

The Komatsu 3D88E is a vertical, in-line, 3-cylinder, water-cooled, four-cycle diesel engine widely implemented across Komatsu's compact utility and construction machinery, such as mini-excavators. Developed on a high-durability block architecture shared with Yanmar’s TNV industrial line, this emissionised engine family is engineered to provide high torque outputs at lower operational speeds while minimizing environmental impact. The engine utilizes either a high-efficiency indirect or an advanced direct injection system depending on the specific model series (such as the Tier 4 Final compliant 3D88E-7), optimizing the combustion envelope for reduced fuel consumption, suppressed thermal fatigue, and compliance with modern emission regulations.

Valve Configuration: Overhead valve configuration with 2 valves per cylinder (1 intake valve and 1 exhaust valve per cylinder, making a total of 6 valves). The valves are actuated via a traditional pushrod and rocker arm mechanism driven by a gear-train camshaft. Cylinder Bore: 88 mm. Piston Stroke: 90 mm. Total Displacement: 1.64 liters (1642 cc). Thermal regulation is managed by a forced-circulation, liquid-cooled cooling system containing an engine-driven centrifugal water pump. Coolant is pumped through the internal passages of the cylinder block and cylinder head to absorb combustion heat, passing through a pellet-type wax thermostat. The system is pressurized and paired with a coolant expansion/recovery tank.

Fuel delivery is managed via an inline mechanical fuel injection pump or high-pressure injection system timed strictly to the engine gear train. Fuel is drawn from the machine's supply tank by an electric or mechanical fuel lift pump, passing through a primary water separator and a high-efficiency spin-on fuel filter to isolate fine particulates. The pressurized fuel is then routed into the fuel injection pump which distributes metered doses to individual direct-injection fuel injectors at precise intervals. Excess fuel from the injectors and the injection pump is routed through a fuel return line circuit back into the primary supply tank.

The engine incorporates a full-pressure, forced lubrication system driven by a trochoid-type oil pump integrated directly into the gear-case housing. Engine oil is pulled from the lower oil pan through a wire-mesh suction strainer and is forced through a spin-on full-flow cartridge oil filter before entering the main oil gallery. The main gallery distributes pressurized oil directly to the crankshaft main bearings, connecting rod journals, camshaft bearings, and up to the overhead rocker arm assembly. Excess pressure is controlled via an integrated oil pressure regulating valve. A crankcase oil vapor recirculation layout is utilized to maintain neutral crankcase pressure.

General Technical Data

Engine Specifications

Engine Model ............... Komatsu 3D88E
Engine Type ............... 4-cycle inline 3-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.46 (88.0)
Engine Stroke, in (mm) ............... 3.54 (90.0)
Displacement, cu.in (L) ............... 100.2 (1.642)
Rated Engine Power, hp (kW) ............... 24.4-33.0 (18.2-24.6)
Rated Engine Speed, rpm ............... 2000-3000
Peak Torque ............... 63.4-78.2 lb-ft (86.0-106.0 Nm) at 1800-2000 rpm
Low Idle Speed, rpm ............... 1150-1250
High Idle Speed, rpm ............... 2595-2645
Operating Speed ............... 2400 rpm
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 19.0:1
Firing Order ............... 1-3-2
Combustion System ............... Direct injection combustion chamber
Piston Type ............... Aluminum alloy with toroidal bowl strut cavity
Camshaft Type ............... Forged alloy chill hardened lobes gear driven
Valve Mechanism ............... Pushrod actuated overhead valve
Cylinder Block Type ............... Cast iron mono-block
Cylinder Head Type ............... Cast iron overhead valve cross-flow
Lubrication System ............... Full-pressure trochoid pump feed
Oil Pump Type ............... Gear-driven trochoid pump
Oil Filter Type ............... Full-flow spin-on cartridge
Cooling System ............... Liquid-cooled forced circulation
Water Pump Type ............... Belt-driven centrifugal pump
Air Cleaner Type ............... Dry dual-element radial seal
Emissions Certification ............... EPA Tier 4 Final standard configuration
Starting System ............... Electric motor starter
Electrical System ............... 12V
Alternator Rating ............... 40A or 55A

Fuel System

Fuel Injection Pump ............... Yanmar MP multi-plunger inline type assembly
Governor Type ............... Mechanical centrifugal all-speed type
Governor Control ............... Mechanical centrifugal type governor device
Fuel Feed Pump ............... Electromagnetic diaphragm pump delivery unit
Fuel Injection Nozzle ............... Hole type multi-orifice precision nozzle
Nozzle Opening Pressure, psi (MPa) ............... 2843-2988 (19.6-20.6)
Fuel Filter Type ............... Spin-on element with water separator bowl
Injection Timing ............... 14-16 degrees BTDC
Fuel Spray Angle ............... 150 degree conical spray orientation setup
Plunger Diameter, in (mm) ............... 0.236 (6.00)
Plunger Stroke, in (mm) ............... 0.276 (7.00)
Delivery Valve Opening Pressure, psi (MPa) ............... 217-290 (1.50-2.00)
Fuel Return Line Max Pressure, psi (MPa) ............... 2.84 (0.02)
Fuel Line Outer Diameter, in (mm) ............... 0.236 (6.00)
Fuel Line Inner Diameter, in (mm) ............... 0.079 (2.00)
Transfer Pump Pressure, psi (MPa) ............... 2.9-4.3 (0.02-0.03)
Fuel Grade Specification ............... ASTM D975 No. 2-D ultra low sulfur fuel std
Nozzle Hole Number ............... 5 precision laser cut atomization orifices drill pattern
Nozzle Hole Diameter, in (mm) ............... 0.008 (0.20)
Injection Pipe Length, in (mm) ............... 15.75 (400.00)
Injection Pipe Wall Thickness, in (mm) ............... 0.079 (2.00)
Maximum Injection Pressure, psi (MPa) ............... 11603 (80.00)
Fuel Tank Vent Venting Sizing, in (mm) ............... 0.118 (3.00)

Dimensions and Weight

Overall Length, in (mm) ............... 21.7 (550)
Overall Width, in (mm) ............... 18.9 (480)
Overall Height, in (mm) ............... 24.2 (615)
Dry Weight, lbs (kg) ............... 305 (139)
Wet Weight, lbs (kg) ............... 329 (149)

Maintenance Data

Service Information

Standard Compression Pressure, psi (MPa) ............... 426-483 (2.94-3.33)
Minimum Compression Pressure, psi (MPa) ............... 341 (2.35)
Maximum Pressure Between Cylinders, psi (MPa) ............... 28-43 (0.19-0.30)
Oil Pressure at Idle Speed, psi (MPa) ............... 8.5 (0.06)
Oil Pressure at Rated Speed, psi (MPa) ............... 43-57 (0.29-0.39)
Cooling System Cap Relief Pressure, psi (kPa) ............... 12.8 (88.3)
Thermostat Start Opening Temp, F (C) ............... 160 (71.0)
Thermostat Full Open Temp, F (C) ............... 185 (85.0)
Fan Belt Tension Deflection, in (mm) ............... 0.39-0.59 (10.0-15.0)
Intake Valve Clearance (Cold), in (mm) ............... 0.008 (0.20)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.008 (0.20)

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 with Filter, qt (L) ............... 7.08 (6.70)
Engine Oil Capacity, Pan Only, qt (L) ............... 6.34 (6.00)
Coolant Capacity, Engine Block, qt (L) ............... 2.11 (2.00)

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, in (mm) ............... 3.4646-3.4650 (88.000-88.010)
Cylinder Bore Roundness Taper, in (mm) ............... 0.0004 (0.010)
Cylinder Head Flatness, Limit, in (mm) ............... 0.0020 (0.05)
Cylinder Head Rebuild Warpage, in (mm) ............... 0.0059 (0.15)
Main Journal Outer Diameter, in (mm) ............... 1.9646-1.9650 (49.900-49.910)
Crankpin Journal Diameter, in (mm) ............... 1.8858-1.8862 (47.900-47.910)
Main Journal Bearing Clearance, in (mm) ............... 0.0015-0.0027 (0.038-0.068)
Crankpin Bearing Clearance, in (mm) ............... 0.0015-0.0026 (0.038-0.066)
Crankshaft End Play, in (mm) ............... 0.0043-0.0083 (0.110-0.210)
Connecting Rod Small End Bushing I.D , in (mm) ............... 1.0240-1.0244 (26.010-26.020)
Small End Bushing Clearance, in (mm) ............... 0.0004-0.0010 (0.010-0.025)
Connecting Rod Big End Side Play, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Piston Skirt Outer Diameter, in (mm) ............... 3.4624-3.4628 (87.945-87.955)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0018-0.0026 (0.045-0.065)
Piston Pin Bore Inner Diameter, in (mm) ............... 1.0236-1.0240 (26.000-26.010)
Piston Pin Outer Diameter, in (mm) ............... 1.0234-1.0236 (25.995-26.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0020 (0.050)
Top Ring Groove Width, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Second Ring Groove Width, in (mm) ............... 0.0787-0.0793 (2.000-2.015)
Oil Ring Groove Width, in (mm) ............... 0.1181-0.1187 (3.000-3.015)
Top Ring Side Clearance, in (mm) ............... 0.0035-0.0047 (0.090-0.120)
Second Ring Side Clearance, in (mm) ............... 0.0016-0.0031 (0.040-0.080)
Oil Ring Side Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Top Ring End Gap, in (mm) ............... 0.0098-0.0157 (0.250-0.400)
Second Ring End Gap, in (mm) ............... 0.0098-0.0157 (0.250-0.400)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2736-0.2742 (6.950-6.965)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2732-0.2738 (6.940-6.955)
Valve Guide Inner Diameter, in (mm) ............... 0.2756-0.2762 (7.000-7.015)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0014-0.0026 (0.035-0.065)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0018-0.0030 (0.045-0.075)
Valve Seat Sink Depth, in (mm) ............... 0.0138-0.0217 (0.350-0.550)
Valve Spring Free Length, in (mm) ............... 1.4882 (37.800)
Camshaft Main Journal Diameter, in (mm) ............... 1.5728-1.5736 (39.950-39.970)
Camshaft Journal Bearing Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Cam Lobe Height, in (mm) ............... 1.3406-1.3484 (34.050-34.250)
Camshaft Deflection Runout Distortion, in (mm) ............... 0.0008 (0.020)
Tappet Body Outer Diameter, in (mm) ............... 0.4705-0.4713 (11.950-11.970)
Tappet Guide Bore Inner Diameter, in (mm) ............... 0.4724-0.4731 (12.000-12.018)
Tappet Body to Guide Clearance, in (mm) ............... 0.0012-0.0027 (0.030-0.068)
Rocker Shaft Outer Diameter, in (mm) ............... 0.6283-0.6291 (15.960-15.980)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.6299-0.6307 (16.000-16.020)
Rocker Arm Shaft to Bushing Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Idler Gear Shaft Outer Diameter, in (mm) ............... 1.4547-1.4555 (36.950-36.970)
Idler Gear Bushing Inner Diameter, in (mm) ............... 1.4567-1.4577 (37.000-37.025)
Idler Gear Shaft to Bushing Clearance, in (mm) ............... 0.0012-0.0030 (0.030-0.075)

Tightening Torques

Cylinder Head Bolts (Step One), lb-ft (Nm) ............... 30.3 (41.1)
Cylinder Head Bolts (Final Step), lb-ft (Nm) ............... 62.9 (85.3)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 68.7-72.4 (93.2-98.1)
Connecting Rod Cap Nut, lb-ft (Nm) ............... 32.5-36.1 (44.1-49.0)
Flywheel Mounting Flange Bolt, lb-ft (Nm) ............... 61.4-65.0 (83.3-88.1)
Camshaft Thrust Plate Bolt, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Crankshaft Pulley Center Hub Bolt, lb-ft (Nm) ............... 83.2-90.3 (112.8-122.4)
Timing Gear Case Cover Outer Shell, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Rocker Arm Shaft Support Bolt, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Valve Clearance Adjuster Locknut, lb-ft (Nm) ............... 12.3-15.9 (16.7-21.6)
Valve Rocker Arm Cover Cap Nut, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Oil Pan Mount Outer Perimeter Bolt, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Oil Pan Fluid Drain Hex Plug, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Fuel Injection Pump Mount Flange Bolt, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Fuel Injection Pump Drive Gear Nut, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Fuel Injection High Pressure Line Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Injection Nozzle Holder Assembly, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Fuel Nozzle Leak Off Line Union Nut, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel Feed Line Diaphragm Pump Nut, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Exhaust Manifold Flange Stud Nut, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Intake Manifold Cast Runner Inlet Bolt, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Water Pump Body Assembly Flange Bolt, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Thermostat Housing Cover Screw, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Cooling Fan Drive Pulley Stud Nut, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Starter Motor Housing Mounting Flange Bolt, lb-ft (Nm) ............... 32.5-39.7 (44.1-53.9)
Alternator Pivoting Bracket Base Bolt, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Alternator Tension Adjusting Locking Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pressure Sensor Sender Unit Screw, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Coolant Temperature Indicator Unit, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Glow Plug Main Terminal Hex Body Bolt, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Glow Plug Electrical Power Connector Rail Nut, lb-ft (Nm) ............... 1.1-1.5 (1.5-2.0)
Oil Pump Cover Plate Cross Machine Screw, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Oil Cooler Central Bypass Valve, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Oil Filter Housing Base Mount Bolt, lb-ft (Nm) ............... 17.7-21.7 (24.0-29.4)
Flywheel Housing Backing Frame Bolt, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Rear Crankshaft Oil Seal Case Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Breather Valve Cover Flange Screw, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Pre-Cleaner Bracket Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)

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