Isuzu 3KR2 Specifications
| Engine Model: Isuzu 3KR2 |
| Engine Type: 4-stroke in-line 3-cylinder liquid-cooled diesel |
| Total Displacement: 89 cu.in (1.46 L) |
| Rated Engine Power: 30-35 Hp (22-26 kW) at 2400 rpm |
| Fuel System Type: Indirect injection |
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The Isuzu 3KR2 is a 1.5-liter, 3-cylinder
industrial diesel engine designed for heavy-duty machinery including
mini excavators, compact loaders, and forklifts. It represents an
updated version of the earlier 3KR1 model, featuring revised tuning and
accessory mounting configurations for enhanced durability in demanding
applications. This engine employs indirect injection with a swirl
combustion chamber, promoting smoother operation and reduced noise
compared to direct injection designs.
The naturally aspirated 3KR2 is constructed around a cast iron block
with replaceable cylinder liners, allowing in-frame overhaul without
complete engine removal. Widely used in Hitachi EX30, EX35, and EX40UR
excavators as well as IHI compact machinery, this engine produces
approximately 23 hp at rated speed. The firing order follows a 1-3-2
sequence, distinct from four-cylinder configurations.
Engine Type: Inline 3-cylinder, 4-cycle, vertical water-cooled diesel
Number of Cylinders: 3
Displacement: 1.46-1.50 L (89 cu-in)
Bore x Stroke: 81 mm x 82 mm (3.19 in x 3.23 in)
Compression Ratio: 21.0:1 (indirect injection)
Aspiration: Naturally aspirated
Combustion System: Indirect injection (pre-combustion chamber)
Firing Order: 1-3-2
Rated Power (Hitachi EX30): 17 kW (23 hp) at 2200-2400 rpm
Maximum Power Range: 22-26 kW (30-35 hp)
Peak Torque: 85-95 Nm (63-70 lb-ft) at 1600-1800 rpm
Low Idle Speed: 1100 rpm
High Idle Speed (no load): 2600-2750 rpm
Rotation (facing flywheel): Counter-clockwise
Fuel Type: Diesel (JIS K-2204 No. 2)
The cylinder block is fabricated from cast iron with a deep-skirt design
for structural rigidity under continuous industrial loads. It
incorporates four main bearing supports to maintain crankshaft
alignment. A distinctive feature is the use of replaceable wet cylinder
liners, allowing in-chassis overhaul without removing the engine from
the machinery.
The liners are in direct contact with engine coolant through precisely
machined ports in the block, providing efficient heat dissipation from
the combustion zone. The block includes integrated oil galleries serving
the crankshaft, camshaft, and piston cooling jets. Piston specifications
include rings with thicknesses of 2.0 mm, 1.75 mm, and 4.0 mm for the
compression and oil control functions.
The cylinder head is manufactured from cast iron or aluminum alloy
depending on the production series, with high heat resistance materials
selected for durability under sustained operation. Each cylinder
receives two valves: one intake and one exhaust, totaling six valves for
the entire engine. The overhead valve (OHV) configuration uses pushrods
and rocker arms actuated by a camshaft located within the cylinder
block.
Valve clearance adjustment is performed by loosening a locknut and
turning an adjusting screw on the rocker arm. Valve Clearance (Cold -
Intake): 0.25 mm (0.010 in). Valve Clearance (Cold - Exhaust): 0.25 mm
(0.010 in). The cylinder head gasket is a steel or composite design
capable of withstanding indirect injection pressures.
The engine employs a mechanical indirect injection system. A Bosch or
Zexel inline injection pump (depending on the application) meters and
distributes fuel to individual injection lines. The pump includes a
mechanical governor that maintains engine speed under varying loads by
adjusting fuel delivery. Pencil-type injectors with a preset opening
pressure are installed one per cylinder, positioned to inject fuel into
a pre-combustion chamber (swirl chamber) located in the cylinder head.
This chamber creates turbulence that mixes fuel with air before
combustion proceeds into the main cylinder. A feed pump, mounted on the
injection pump body, draws fuel from the tank through a primary filter
(water separator) before supplying the secondary spin-on fuel filter.
Excess fuel returns to the tank through a leak-off line.
Oil Capacity (with filter): 7.0 L (7.4 US qt)
Oil Pressure at rated speed: 35-50 psi (2.4-3.4 bar)
Oil Pressure at low idle (minimum): 10 psi (0.7 bar)
Recommended Oil Grade: SAE 15W-40 or 10W-30 (API CD, CE, or CF)
Oil Filter: Full-flow spin-on type with integral bypass valve
System Features: A gear-type oil pump mounted on the front of the
crankshaft draws oil through a strainer inside the oil pan. An oil
cooler, integrated into the coolant circuit on some applications,
maintains oil temperature within safe limits. Piston cooling jets are
installed in the crankcase on certain variants.
Coolant Capacity (engine only): 5.0 L (5.3 US qt)
Coolant Capacity (with radiator): 7.0-8.5 L (7.4-9.0 US qt)
Thermostat opening temperature: 76.5°C (170°F)
Thermostat fully open temperature: 90°C (194°F)
Coolant Type: Ethylene glycol-based with corrosion inhibitors
Water Pump: Belt-driven centrifugal type with cast iron housing
System Features: A bypass thermostat circuit maintains rapid warm-up and
prevents thermal shock. The cooling system includes a separate circuit
for the oil cooler where equipped. A coolant recovery tank is standard
on most industrial applications.
Electrical System: 12 volt with 45-65 ampere-hour battery capacity
Starter Motor: 12V, pre-engaged type with solenoid, rated at 1.8-2.2 kW
Alternator: 12V, 35-45 ampere output
Air Intake System: Dry-type two-stage air cleaner with a vacuum
restriction indicator. The system includes a cyclone pre-filter for
heavy dust environments.
Exhaust System: Cast iron exhaust manifold with a single outlet. Muffler
specifications vary by machinery application.
Governor: Mechanical centrifugal type integrated into the injection
pump, providing variable speed control for industrial equipment.
Dry Weight: 154-160 kg (340-353 lb)
Length (front to rear): 570 mm (22.4 in)
Width: 460 mm (18.1 in)
Height: 670 mm (26.4 in)
Oil Pan Depth: 120 mm (4.7 in) for standard sump
Engine Oil Change Interval: 250 hours under normal industrial duty.
Engine Oil Change Interval (severe service): 150 hours.
Oil Filter Change: Every oil change.
Fuel Filter Change (secondary): 500 hours.
Fuel Filter Change (primary/water separator): 250 hours.
Valve Clearance Inspection Interval: 500 hours.
Air Cleaner Service Interval: 250 hours maximum.
Coolant Change Interval: 1000 hours or 12 months.
Injector Inspection Interval: 1000 hours.
Injection Timing (static): 12°-14° BTDC.
Valve Clearance Adjustment (cold, intake/exhaust): 0.25 mm (0.010 in).
Cylinder Head Bolts (Step 1): 50 Nm (37 lb-ft)
Cylinder Head Bolts (Step 2): 80 Nm (59 lb-ft)
Cylinder Head Bolts (Step 3 - final): 110 Nm (81 lb-ft)
Connecting Rod Bolts: 45 Nm (33 lb-ft) + 60° angle turn
Main Bearing Cap Bolts: 75 Nm (55 lb-ft)
Flywheel Bolts: 50 Nm (37 lb-ft) + 90° angle turn
Crankshaft Pulley Bolt: 150 Nm (110 lb-ft)
Rocker Arm Shaft Bracket Bolts: 22 Nm (16 lb-ft)
Valve Rocker Adjusting Locknut: 20 Nm (15 lb-ft)
Injection Pump Drive Gear Nut: 60 Nm (44 lb-ft)
Injection Pump Mounting Nuts: 25 Nm (18 lb-ft)
Injector Clamp Bolts: 23 Nm (17 lb-ft)
Oil Pan Bolts: 12 Nm (9 lb-ft)
Water Pump Mounting Bolts: 18 Nm (13 lb-ft)
Starter Motor Mounting Bolts: 30 Nm (22 lb-ft)
Alternator Mounting Bracket Bolts: 25 Nm (18 lb-ft)
Front Timing Gear Cover Bolts: 10 Nm (7 lb-ft)
The Isuzu 3KR2 engine is installed in numerous construction and
industrial machinery types manufactured from approximately 1983 through
2001.
Mini Excavators: Hitachi EX30, EX35, EX40UR, EX40UR-2. Also found in IHI
28G, 28J, and AX30-2 models.
Forklifts: Various 2-3 ton capacity forklifts from multiple
manufacturers using Isuzu power units.
Compact Loaders: Skid steer loaders and compact track loaders from OEM
builders.
Industrial Power Units: Stationary units for hydraulic pump drives,
small air compressors, and agricultural implements.
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