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Isuzu 3KR2 Engine

The Isuzu 3KR2 is a heavy-duty, industrial 3-cylinder diesel engine engineered for demanding off-road applications, including mini-excavators (such as the Hitachi EX30), forklifts, generators, and light construction equipment. Developed as a robust successor to the 3KR1 platform, the 3KR2 features optimized horsepower and RPM tuning configurations to sustain reliability under extreme duty cycles. The block design features cast iron construction with high mechanical durability, utilizing a compact inline configuration.

The cylinder head utilizes an Overhead Camshaft (OHC) valve configuration. The single overhead camshaft acts directly upon the intake and exhaust valves via rocker arm assemblies. Camshaft drive timing is managed through a synchronized gear and chain system linked directly to the crankshaft. The engine features a cylinder geometry consisting of a 81 mm bore combined with a 92 mm stroke. This long-stroke configuration optimizes low-end torque delivery and combustion efficiency. The standard total piston displacement calculated across the three cylinders is 1422 cc.

The fuel architecture relies on an indirect injection (IDI) design featuring an inline swirl combustion chamber setup. Fuel is pressurized by a mechanical Bosch-type inline injection pump assembly. A mechanical all-speed governor controls the injection pump plunger stroke to match fuel delivery to load variations. High-pressure lines connect the pump directly to the throttling-type fuel injection nozzles, which atomize the fuel spray directly into the swirl chambers for clean, stable combustion.

Lubrication is managed via a full-pressure feed system driven by a trochoid-type oil pump. Oil is drawn through an inlet strainer in the oil pan and routed through a full-flow, spin-on oil filter element. Pressurized oil channels in the crankcase deliver consistent lubrication to the main bearings, connecting rod journals, and up through the cylinder block to the overhead camshaft assembly and rocker arms.

The engine uses a forced-circulation, liquid-cooled thermal management system. A centrifugal water pump driven by a V-belt draws coolant through the radiator block and forces it through internal water jackets surrounding the cylinders and combustion chambers. System temperature tracking is governed by a pellet-type thermostat that limits flow to the bypass circuit until optimal operating temperatures are achieved.

General Technical Data

Engine Specifications

Engine Model ............... Isuzu 3KR2
Engine Type ............... 4-cycle inline 3-cylinder overhead cam liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.19 (81.0)
Engine Stroke, in (mm) ............... 3.62 (92.0)
Displacement, cu.in (L) ............... 86.8 (1.422)
Rated Engine Power, hp (kW) ............... 32.0 (23.9)
Rated Engine Speed, rpm ............... 3000
Peak Torque, lb-ft (Nm) ............... 64.9 (88.0) at 1800 rpm
Idle Speed, rpm ............... 800-900
Maximum No-Load Speed, rpm ............... 3200-3300
Aspiration Type ............... Naturally aspirated
Compression Ratio ............... 22.0:1
Firing Order ............... 1-3-2
Direction of Rotation ............... Counterclockwise viewed from flywheel
Valve Mechanism System ............... Overhead valve, gear-driven camshaft
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Full-pressure
Oil Pump Type ............... Trochoid gear-driven
Oil Filter Type ............... Full-flow, spin-on
Cooling System ............... Liquid-cooled
Water Pump Type ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System ............... 12V
Alternator Capacity, A ............... 20-35

Fuel System

Injection Pump Type ............... Bosch P-type mini inline
Governor Type ............... Mechanical centrifugal RSV
Injection Timing, deg BTDC ............... 14.0
Injection Pressure, psi (bar) ............... 1990.0 (137.2)
Injector Nozzle Type ............... Throttle multi-hole type
Fuel Transfer Pump Type ............... Mechanical piston type
Fuel Filter Type ............... Cartridge spin-on element
Maximum Fuel Lift, ft (m) ............... 3.3 (1.0)
Feed Pump Delivery Pressure, psi (bar) ............... 2.8 (0.19)
Fuel Return Line Layout ............... Overhead spill-pipe to tank
Fuel Tank Venting Type ............... Open atmosphere vent
Injection Pipe Outer Diameter, in (mm) ............... 0.23 (6.0)
Injection Pipe Inner Diameter, in (mm) ............... 0.07 (2.0)

Dimensions and Weight

Overall Length, in (mm) ............... 21.8 (555)
Overall Width, in (mm) ............... 18.1 (460)
Overall Height, in (mm) ............... 23.4 (595)
Dry Weight, lbs (kg) ............... 282 (128)
Wet Weight with Fluids, lbs (kg) ............... 305 (138)

Maintenance Data

Service Information

Standard Compression Pressure, psi (MPa) ............... 441.0 (3.04)
Minimum Compression Pressure, Limit, psi (MPa) ............... 370.0 (2.55)
Compression Pressure Between Cylinders, psi (MPa) ............... 28.4 (0.19)
Oil Pressure at Idle Speed, psi (kPa) ............... 14.2 (98.0)
Oil Pressure at Rated Speed, psi (kPa) ............... 42.6-56.8 (294.0-392.0)
Radiator Cap Pressure Valve Relief Setting, psi (kPa) ............... 12.8 (88.2)
Coolant Operating Temperature Range, F (C) ............... 176.0-194.0 (80.0-90.0)
Thermostat Opening Start Temperature, F (C) ............... 170.0 (76.5)
Thermostat Fully Open Temperature, F (C) ............... 194.0 (90.0)
Fan Belt Deflection, Standard Push Force, lbs (N) ............... 22.0 (98.0)
Fan Belt Deflection, Under Standard Force, in (mm) ............... 0.39-0.47 (10.0-12.0)
Intake Valve Clearance (Cold), in (mm) ............... 0.012 (0.25)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.012 (0.25)

Engine Oil and Coolant

Engine Oil Type .................. SAE 20W-20, 10W-30, or SAE 15W-40
API Service Classifications ......................... CD or CE
Engine Oil Capacity, High Level, qts (L) ............... 4.75 (4.5)
Engine Oil Capacity, Low Level, qts (L) ............... 3.17 (3.0)
Oil Filter Element Fluid Capacity, qts (L) ............... 0.31 (0.3)
Total Engine Oil Capacity, qts (L) ............... 5.07 (4.8)
Coolant Capacity, Internal Passages, qts (L) ............... 2.32 (2.2)

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 500 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 2000 hours
Compression test ............... Every 1000 hours
Belt inspection ............... Every service cycle

Service Specifications

Cylinder Block Top Surface Flatness, in (mm) ............... 0.002 (0.05)
Cylinder Liner Inside Diameter (Grade A), in (mm) ............... 3.1889-3.1893 (81.000-81.011)
Cylinder Liner Inside Diameter (Grade B), in (mm) ............... 3.1893-3.1897 (81.011-81.022)
Cylinder Liner Cylindricity and Taper Std Value, in (mm) ............... 0.0004 (0.01)
Cylinder Liner Projection Above Block Top Surface, in (mm) ............... 0.0023-0.0035 (0.06-0.09)
Crankshaft Crankpin Journal Diameter, in (mm) ............... 1.8881-1.8887 (47.959-47.975)
Crankshaft Main Journal Diameter, in (mm) ............... 2.0456-2.0462 (51.959-51.975)
Crankshaft Main Bearing Oil Clearance, in (mm) ............... 0.0013-0.0029 (0.034-0.073)
Crankshaft End Play, in (mm) ............... 0.0023-0.0055 (0.060-0.140)
Crankshaft Main Journal Thrust Bearing Width, in (mm) ............... 0.8228-0.8244 (20.900-20.940)
Crankshaft Center Journal Width, in (mm) ............... 0.8267-0.8283 (21.000-21.042)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.9845-0.9851 (25.008-25.023)
Connecting Rod Big End Side Clearance, in (mm) ............... 0.0039-0.0078 (0.10-0.20)
Connecting Rod Bearing Oil Clearance, in (mm) ............... 0.0014-0.0029 (0.035-0.074)
Piston Pin to Small End Bushing Clearance, in (mm) ............... 0.0003-0.0011 (0.008-0.028)
Piston Outer Diameter (Grade A), in (mm) ............... 3.1866-3.1870 (80.941-80.952)
Piston Outer Diameter (Grade B), in (mm) ............... 3.1870-3.1874 (80.952-80.963)
Piston to Cylinder Liner Clearance, in (mm) ............... 0.0018-0.0027 (0.047-0.070)
Top Ring Groove Width, in (mm) ............... 0.081-0.082 (2.05-2.07)
Second Ring Groove Width, in (mm) ............... 0.080-0.081 (2.03-2.05)
Oil Ring Groove Width, in (mm) ............... 0.158-0.159 (4.01-4.03)
Top Ring Side Clearance, in (mm) ............... 0.0023-0.0035 (0.06-0.09)
Second Ring Side Clearance, in (mm) ............... 0.0019-0.0031 (0.05-0.08)
Oil Ring Side Clearance, in (mm) ............... 0.0011-0.0027 (0.03-0.07)
Top Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.20-0.35)
Second Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.20-0.35)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0177 (0.20-0.45)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.9844-0.9846 (25.005-25.011)
Piston Pin Outer Diameter, in (mm) ............... 0.9841-0.9843 (24.995-25.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0001-0.0006 (0.005-0.016)
Cylinder Head Lower Surface Flatness, in (mm) ............... 0.0019 (0.05)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2736-0.2742 (6.950-6.965)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2724-0.2732 (6.920-6.940)
Valve Guide Inside Diameter, in (mm) ............... 0.2755-0.2761 (7.000-7.015)
Intake Valve Stem to Valve Guide Clearance, in (mm) ............... 0.0013-0.0025 (0.035-0.065)
Exhaust Valve Stem to Valve Guide Clearance, in (mm) ............... 0.0023-0.0037 (0.060-0.095)
Intake Valve Seat Contact Width, in (mm) ............... 0.0472-0.0551 (1.20-1.40)
Exhaust Valve Seat Contact Width, in (mm) ............... 0.0472-0.0551 (1.20-1.40)
Valve Spring Free Length, in (mm) ............... 1.665 (42.3)
Camshaft Journal Outer Diameter (Front), in (mm) ............... 1.5731-1.5739 (39.959-39.975)
Camshaft Journal Outer Diameter (Middle), in (mm) ............... 1.5338-1.5344 (38.959-38.975)
Camshaft Journal Outer Diameter (Rear), in (mm) ............... 1.4944-1.4950 (37.959-37.975)
Camshaft Journal Bearing Oil Clearance, in (mm) ............... 0.0009-0.0029 (0.025-0.075)
Cam Lobe Height (Intake), in (mm) ............... 1.3051 (33.150)
Cam Lobe Height (Exhaust), in (mm) ............... 1.3051 (33.150)
Camshaft End Play, in (mm) ............... 0.0019-0.0059 (0.050-0.150)
Tappet Outer Diameter, in (mm) ............... 0.4712-0.4718 (11.970-11.985)
Cylinder Block Tappet Guide Bore ID, in (mm) ............... 0.4724-0.4731 (12.000-12.018)
Tappet to Tappet Guide Bore Clearance, in (mm) ............... 0.0005-0.0018 (0.015-0.048)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4714-0.4720 (11.973-11.988)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.4724-0.4736 (12.000-12.030)
Rocker Arm to Shaft Radial Oil Clearance, in (mm) ............... 0.0004-0.0022 (0.012-0.057)

Tightening Torques

Cylinder Head Bolt, lb-ft (Nm) ............... 83.2-97.6 (112.8-132.4)
Main Bearing Cap Bolt, lb-ft (Nm) ............... 54.2-61.5 (73.5-83.4)
Connecting Rod Cap Nut, lb-ft (Nm) ............... 54.2-61.5 (73.5-83.4)
Flywheel Bolt, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Crankshaft Damper Pulley Bolt, lb-ft (Nm) ............... 108.5-122.9 (147.1-166.7)
Camshaft Gear Bolt, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Rocker Arm Shaft Bracket Bolt, lb-ft (Nm) ............... 15.9-21.7 (21.6-29.4)
Cylinder Head Cover Nut, lb-ft (Nm) ............... 5.8-8.7 (7.8-11.8)
Oil Pan Drain Plug, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Oil Pan Mounting Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Timing Gear Case Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Timing Gear Case Cover Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Injection Pump Drive Gear Nut, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Injection Pump Retaining Nut, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Injection Nozzle Assembly Holder, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Injection Pipe Gland Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Overflow Pipe Clip Bolt, lb-ft (Nm) ............... 5.8-8.7 (7.8-11.8)
Glow Plug Torque, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Oil Pressure Switch, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Water Temperature Sensor, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Cooling Fan Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Water Pump Mounting Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Thermostat Housing Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Intake Manifold Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Exhaust Manifold Bolt, lb-ft (Nm) ............... 15.9-21.7 (21.6-29.4)
Starter Motor Mounting Bolt, lb-ft (Nm) ............... 54.2-61.5 (73.5-83.4)
Alternator Mounting Bolt Main, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Alternator Adjusting Lock Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Oil Pump Cover Plate Screw, lb-ft (Nm) ............... 3.6-5.1 (4.9-6.9)
Oil Relief Valve Plug, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Flywheel Housing Bolt, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Rear Oil Seal Retainer Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Front Oil Seal Retainer Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Main Oil Gallery End Plug, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Idler Gear Shaft Bolt, lb-ft (Nm) ............... 18.1-24.6 (24.5-33.3)

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• Isuzu Engines Specs
  
• Isuzu 3KC1 Specs
  
• Isuzu 3KC2 Specs
  
• Isuzu 3KR1 Specs
  
• Isuzu 3LB1 Specs
  
• Isuzu 3LD1 Specs
  
• Isuzu 3LD2 Specs
  

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