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Komatsu 4D94E Engine

The Komatsu 4D94E is a heavy-duty, vertical, in-line, 4-cycle, water-cooled diesel engine engineered primarily for standard forklift trucks, small construction equipment, and agricultural vehicles. Developed in cooperation with Yanmar (closely resembling the 4TNE94 series), this naturally aspirated, four-cylinder power unit utilizes a high-strength cast iron cylinder block and a swirl-type combustion chamber layout designed for stable low-speed torque and low vibration. It features a traditional gear-driven camshaft train, an overhead valve setup, and a fully mechanical fuel management system, offering high reliability and straightforward serviceability under heavy continuous operation.

The engine uses an overhead valve (OHV) arrangement actuated via a block-mounted camshaft, pushrods, and rocker arm assemblies. It has two valves per cylinder (one intake and one exhaust). The baseline cylinder bore diameter is exactly 94.0 mm (3.70 in). The piston stroke length is 100.0 mm (3.937 in) for the standard 4D94E and 4D94E-1A variants, resulting in a total engine displacement of 2.77 liters. The cooling architecture relies on a forced-circulation liquid-cooled system. Coolant movement is maintained by a belt-driven water pump that circulates fluid through an external radiator and an engine-mounted cooling fan.

Fuel System: This engine features a mechanical fuel injection system built around a distributor VE-type fuel injection pump. The pump assembly includes an all-speed mechanical governor along with a specialized reverse revolution prevention mechanism. Fuel is pressurized and delivered to the cylinders via mechanical fuel injection nozzles seated inside indirect-injection swirl combustion chambers. Standard workshop testing procedures require the nozzle injection opening pressure to be calibrated between 12.3 and 13.3 MPa.

Lubrication System: Lubrication is managed via a forced lubrication delivery system driven by an internal trochoid-type oil pump. The system draws oil from the engine oil pan through an inlet oil strainer, feeding it directly through a full-flow engine oil filter. An integrated oil cooler is available as an factory option. The complete lubrication capacity for the system totals 7.5 liters, and the manual specifies API grade class CC or higher oil for standard operations.

General Technical Data

Engine Specifications

Engine Model ............... Komatsu 4D94E
Engine Type ............... 4-cycle inline 4-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 4
Cylinder Arrangement ............... In-line vertical
Engine Bore, mm (in) ............... 94.0 (3.70)
Engine Stroke, mm (in) ............... 100.0 (3.94)
Displacement, L (cu.in) ............... 2.776 (169.4)
Rated Engine Power, kW (hp) ............... 43.3 (58.0) at 2500 rpm
Rated Engine Speed, rpm ............... 2500
Peak Torque ............... 165 Nm (121.7 lb-ft) at 1600 rpm
Low Idle Speed, rpm ............... 750-850
High Idle Speed, rpm ............... 2650-2750
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 18.5:1
Firing Order ............... 1-3-4-2
Combustion Chamber Type ............... Direct injection toroid bowl in piston top
Direction of Rotation ............... Counterclockwise looking from flywheel end
Crankshaft Material ............... Forged steel with induction hardened journals
Connecting Rod Material ............... Forged alloy steel with H-section design
Camshaft Drive Method ............... Helical gear train drive from crankshaft
Valve Mechanism ............... Overhead valve actuated via pushrods and rockers
Cylinder Block Material ............... Cast iron
Cylinder Head Material ............... Cast iron
Lubrication System ............... Forced lubrication by trochoid gear pump
Oil Pump Type ............... Crankshaft gear-driven trochoid pump
Oil Filter Type ............... Full-flow cartridge spin-on element
Cooling System ............... Liquid-cooled with forced radiator circulation
Water Pump Type ............... Belt-driven centrifugal impeller pump
Air Cleaner Type ............... Dry dual-element heavy-duty filtration system
Starting System ............... Electric starter motor actuation
Starter Motor Power, kW (hp) ............... 2.3 (3.1)
Electrical System, V ............... 12
Alternator Capacity, A ............... 40

Fuel System

Fuel Injection Pump Type ............... Bosch VE distributor type pump
Governor Type ............... All-speed mechanical centrifugal governor
Feed Pump Type ............... Vane type integrated inside injection pump
Fuel Injection Timing, deg BTDC ............... 12.0
Fuel Injection Nozzle Type ............... Multi-hole nozzle assembly
Number of Nozzle Orifices ............... 5
Nozzle Orifice Diameter, mm (in) ............... 0.22 (0.0086)
Nozzle Opening Pressure, MPa (psi) ............... 21.6-22.6 (3132-3277)
Fuel Transfer Pump Delivery Pressure, MPa (psi) ............... 0.15-0.25 (21.7-36.2)
Fuel Filter Type ............... Spin-on cartridge with water separator
Fuel Priming Pump Type ............... Manual diaphragm hand plunger pump
Fuel System Air Bleeding Method ............... Manual vent screw configuration
Recommended Fuel Grade ............... Ultra-low sulfur diesel ISO 8217 DMA
Minimum Fuel Cetane Rating ............... 45
Injection Pump Drive Gear Backlash, mm (in) ............... 0.04-0.10 (0.0015-0.0039)
Fuel Injection Pipe Outer Diameter, mm (in) ............... 6.0 (0.236)
Fuel Injection Pipe Inner Diameter, mm (in) ............... 2.0 (0.078)
Nozzle Holder Gasket Thickness, mm (in) ............... 1.0 (0.039)
Plunger Lift at Top Dead Center, mm (in) ............... 1.0 (0.039)

Dimensions and Weight

Overall Length, mm (in) ............... 720 (28.3)
Overall Width, mm (in) ............... 510 (20.0)
Overall Height, mm (in) ............... 690 (27.1)
Dry Weight, kg (lbs) ............... 223 (492)
Wet Weight, kg (lbs) ............... 235 (518)

Maintenance Data

Service Information

Standard Compression Pressure, MPa (psi) ............... 2.84-3.04 (411-440)
Minimum Compression Pressure, MPa (psi) ............... 2.35 (340)
Compression Variation Between Cylinders, MPa (psi) ............... 0.20 (29.0)
Oil Pressure at Idle Speed, MPa (psi) ............... 0.07 (10.1)
Oil Pressure at Rated Speed, MPa (psi) ............... 0.29-0.39 (42.0-56.5)
Maximum Engine Oil Temperature, C (F) ............... 110.0 (230.0)
Thermostat Opening Temperature, C (F) ............... 71.0 (159.8)
Thermostat Full Open Temperature, C (F) ............... 85.0 (185.0)
Drive V-Belt Deflection under 98 N Force, mm (in) ............... 10.0-14.0 (0.39-0.55)
Intake Valve Clearance (Cold), mm (in) ............... 0.20 (0.0078)
Exhaust Valve Clearance (Cold), mm (in) ............... 0.20 (0.0078)

Engine Oil and Coolant

Engine Oil Type .................. SAE 5W-20, SAE 15W-40, SAE 10W-30
API Service Classifications ......................... CH-4 or CI-4
Engine Oil Capacity with Filter, L (qt) ............... 8.2 (8.6)
Engine Oil Capacity (Pan Only), L (qt) ............... 7.4 (7.8)
Cooling System Capacity (Engine), L (qt) ............... 4.2 (4.4)

Service Intervals

Change oil and filter ............... Every 250 hours
Inspect air cleaner ............... Every 100 hours
Replace air cleaner ............... Every 1000 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) ............... 94.000-94.030 (3.7007-3.7019)
Cylinder Bore Wear Limit Diameter, mm (in) ............... 94.200 (3.7086)
Cylinder Bore Roundness, mm (in) ............... 0.020 (0.0007)
Cylinder Bore Taper Limit, mm (in) ............... 0.020 (0.0007)
Cylinder Block Top Surface Flatness, mm (in) ............... 0.050 (0.0019)
Connecting Rod Small End Bushing I.D, mm (in) ............... 30.025-30.038 (1.1820-1.1825)
Connecting Rod Big End Bore Diameter, mm (in) ............... 54.000-54.015 (2.1259-2.1265)
Crankpin Bearing Shell Thickness, mm (in) ............... 1.500-1.510 (0.0590-0.0594)
Crankpin Outer Diameter, mm (in) ............... 50.950-50.970 (2.0059-2.0066)
Connecting Rod Bearing Clearance, mm (in) ............... 0.030-0.080 (0.0011-0.0031)
Connecting Rod Side Play, mm (in) ............... 0.150-0.350 (0.0059-0.0137)
Main Journal Outer Diameter, mm (in) ............... 59.950-59.970 (2.3602-2.3610)
Main Bearing Bore Inner Diameter, mm (in) ............... 64.000-64.020 (2.5196-2.5204)
Main Bearing Shell Thickness, mm (in) ............... 2.000-2.010 (0.0787-0.0791)
Main Bearing Oil Clearance, mm (in) ............... 0.035-0.085 (0.0013-0.0033)
Crankshaft End Play, mm (in) ............... 0.110-0.210 (0.0043-0.0082)
Piston Skirt Outer Diameter, mm (in) ............... 93.940-93.970 (3.6984-3.6996)
Piston to Cylinder Bore Clearance, mm (in) ............... 0.040-0.080 (0.0015-0.0031)
Piston Pin Bore Inner Diameter, mm (in) ............... 30.000-30.006 (1.1811-1.1813)
Piston Pin Outer Diameter, mm (in) ............... 29.992-30.000 (1.1807-1.1811)
Piston Pin to Piston Pin Bore Clearance, mm (in) ............... 0.000-0.014 (0.0000-0.0005)
Piston Pin to Small End Bushing Clearance, mm (in) ............... 0.025-0.046 (0.0009-0.0018)
Top Ring Groove Width, mm (in) ............... 2.040-2.060 (0.0803-0.0811)
Second Ring Groove Width, mm (in) ............... 2.020-2.040 (0.0795-0.0803)
Oil Ring Groove Width, mm (in) ............... 4.015-4.035 (0.1580-0.1588)
Top Ring Thickness, mm (in) ............... 1.970-1.990 (0.0775-0.0783)
Second Ring Thickness, mm (in) ............... 1.970-1.990 (0.0775-0.0783)
Oil Ring Thickness, mm (in) ............... 3.970-3.990 (0.1562-0.1570)
Top Ring Side Clearance, mm (in) ............... 0.050-0.090 (0.0019-0.0035)
Second Ring Side Clearance, mm (in) ............... 0.030-0.070 (0.0011-0.0027)
Oil Ring Side Clearance, mm (in) ............... 0.025-0.065 (0.0009-0.0025)
Top Ring End Gap, mm (in) ............... 0.250-0.400 (0.0098-0.0157)
Second Ring End Gap, mm (in) ............... 0.250-0.400 (0.0098-0.0157)
Oil Ring End Gap, mm (in) ............... 0.200-0.400 (0.0078-0.0157)
Cylinder Head Bottom Surface Flatness, mm (in) ............... 0.030 (0.0011)
Intake Valve Stem Outer Diameter, mm (in) ............... 7.960-7.975 (0.3133-0.3139)
Exhaust Valve Stem Outer Diameter, mm (in) ............... 7.945-7.960 (0.3127-0.3133)
Intake Valve Guide Inner Diameter, mm (in) ............... 8.010-8.025 (0.3153-0.3159)
Exhaust Valve Guide Inner Diameter, mm (in) ............... 8.010-8.025 (0.3153-0.3159)
Intake Valve Stem to Guide Clearance, mm (in) ............... 0.035-0.065 (0.0013-0.0025)
Exhaust Valve Stem to Guide Clearance, mm (in) ............... 0.050-0.080 (0.0019-0.0031)
Intake Valve Sinkage Depth, mm (in) ............... 0.700-0.900 (0.0275-0.0354)
Exhaust Valve Sinkage Depth, mm (in) ............... 0.700-0.900 (0.0275-0.0354)
Valve Seat Angle, deg ............... 45.0
Valve Face Angle, deg ............... 45.0
Valve Seat Contact Width, mm (in) ............... 1.200-1.500 (0.0472-0.0590)
Valve Spring Free Length, mm (in) ............... 42.000 (1.6535)
Camshaft Journal Outer Diameter, mm (in) ............... 44.925-44.950 (1.7687-1.7696)
Camshaft Bearing Inner Diameter, mm (in) ............... 45.000-45.025 (1.7716-1.7726)
Camshaft Journal Oil Clearance, mm (in) ............... 0.050-0.100 (0.0019-0.0039)
Intake Cam Height, mm (in) ............... 38.650-38.750 (1.5216-1.5255)
Exhaust Cam Height, mm (in) ............... 38.650-38.750 (1.5216-1.5255)
Camshaft End Play, mm (in) ............... 0.050-0.150 (0.0019-0.0059)
Rocker Arm Shaft Outer Diameter, mm (in) ............... 15.966-15.984 (0.6285-0.6292)
Rocker Arm Bushing Inner Diameter, mm (in) ............... 16.000-16.018 (0.6299-0.6306)
Rocker Arm Bushing to Shaft Clearance, mm (in) ............... 0.016-0.052 (0.0006-0.0020)
Tappet Lifter Outer Diameter, mm (in) ............... 11.960-11.975 (0.4708-0.4714)
Tappet Lifter Bore Inner Diameter, mm (in) ............... 12.000-12.018 (0.4724-0.4731)
Tappet to Lifter Bore Clearance, mm (in) ............... 0.025-0.058 (0.0009-0.0022)
Crankshaft Gear to Camshaft Gear Backlash, mm (in) ............... 0.040-0.120 (0.0015-0.0047)
Camshaft Gear to Idler Gear Backlash, mm (in) ............... 0.040-0.120 (0.0015-0.0047)
Idler Gear Shaft Outer Diameter, mm (in) ............... 45.950-45.975 (1.8090-1.8100)
Idler Gear Bushing Inner Diameter, mm (in) ............... 46.000-46.025 (1.8110-1.8120)
Idler Gear Shaft to Bushing Clearance, mm (in) ............... 0.025-0.075 (0.0009-0.0029)

Tightening Torques

Cylinder Head Fasteners (Step 1), lb-ft (Nm) ............... 36.9-43.5 (50.0-59.0)
Cylinder Head Fasteners (Step 2), lb-ft (Nm) ............... 76.0-83.3 (103.0-113.0)
Cylinder Head Fasteners (Step 3), lb-ft (Nm) ............... 95.9 (130.0)
Crankshaft Main Bearing Cap Fasteners (Step 1), lb-ft (Nm) ............... 84.8 (115.0)
Crankshaft Main Bearing Cap Fasteners (Step 2), lb-ft (Nm) ............... 99.6-107.0 (135.0-145.0)
Connecting Rod Big End Cap Nut (Step 1), lb-ft (Nm) ............... 22.1 (30.0)
Connecting Rod Big End Cap Nut (Step 2), lb-ft (Nm) ............... 33.2-43.5 (45.0-59.0)
Flywheel Retaining Bolts, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Crankshaft Front Pulley Center Damper Bolt, lb-ft (Nm) ............... 86.7-94.4 (117.6-128.0)
Camshaft Thrust Plate Flange Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Camshaft Timing Drive Gear Center Bolt, lb-ft (Nm) ............... 43.5-50.7 (59.0-68.8)
Idler Gear Support Shaft Core Anchor Bolt, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Timing Gear Case Cover Outer Shell Screws, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Flywheel Housing Rigid Mounting Frame Bolts, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Rocker Arm Shaft Support Bracket Nuts, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Rocker Arm Valve Adjuster Lock Screw Nut, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Valve Rocker Mechanism Top Cover Nut, lb-ft (Nm) ............... 5.1-8.7 (6.9-11.8)
Oil Pan Sump Drain Plug, lb-ft (Nm) ............... 36.2-43.5 (49.0-59.0)
Oil Pan Flange Block Attachment Screws, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Fuel Injection Pump Drive Gear Lock Nut, lb-ft (Nm) ............... 43.5-47.0 (59.0-63.7)
Fuel Injection Pump Housing Flange Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel Injection Nozzle Holder Assembly Nut, lb-ft (Nm) ............... 28.9-32.5 (39.2-44.1)
Fuel Injection High Pressure Line Delivery Nuts, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Injector Fuel Return Leak Off Line Rail Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Glow Plug Core Terminal, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Glow Plug Electrical Power Supply Link Wire Nuts, lb-ft (Nm) ............... 1.4-2.2 (2.0-3.0)
Intake Manifold Casting Core Port Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Exhaust Manifold Core Port Stud Nuts, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Water Pump Assembly Body Shell Block Mount Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Cooling Fan Blade Assembly to Pulley Bolts, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Water Outlet Thermostat Housing Screws, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pump Internal Housing Cap Screws, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Oil Pressure Relief Valve Spring Plug Nut, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Oil Filter Housing Base Adapter Block Bracket Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Cranking Starter Motor Flange Screws, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Alternator Pivot Anchor Bracket Mounting Bolt, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Alternator Slotted Tension Adjuster Link Stabilizer Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Engine Support Cushion Engine Mount Bracket Bolts, lb-ft (Nm) ............... 57.9-72.3 (78.5-98.0)
Oil Pressure Sensor Sender Unit, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Temperature Sensor Sender Head Unit, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Exhaust Pipe Outlet Flange Gasket Connection Nuts, lb-ft (Nm) ............... 25.3-32.5 (34.3-44.1)
Air Intake Heater Element Casting Block Interface Screws, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Crankcase Breather Assembly Valve Cover Mount Bolts, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)

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• Komatsu Engines Specs
  
• Komatsu 4D84 Specs
  
• Komatsu 4D88E Specs
  
• Komatsu 4D94-2 Specs
  
• Komatsu 4D102 Specs
  
• Komatsu 4D105 Specs
  

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