Mitsubishi K4D Specifications
| Engine Model: Mitsubishi K4D |
| Engine Type: 4-cycle inline 4-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 79.6 cu.in (1.31 L) |
| Rated Engine Power: 28 Hp (20.6 kW) at 2700 rpm |
| Fuel System Type: Indirect fuel injection |
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The Mitsubishi K4D engine is a compact,
four-cylinder, four-stroke diesel powerplant designed for light
industrial and construction machinery. This engine is part of
Mitsubishi's industrial diesel family, engineered to provide reliable
power for compact loaders, mini-excavators, and similar equipment. It
features a water-cooled design, an indirect injection combustion system,
and an overhead valve (OHV) layout with a gear-driven camshaft.
Constructed with a cast iron cylinder block and head, the K4D emphasizes
durability, fuel efficiency, and straightforward maintenance in
demanding operational environments. The engine delivers smooth operation
characteristic of a four-cylinder configuration, with a power band
suited to driving hydraulic systems at constant speeds. Its design
prioritizes accessibility for service and longevity, making it a common
power source in a specific class of compact utility machinery from the
late 20th century.
Engine family: Mitsubishi K4 series.
Engine type: Inline-four cylinder, four-stroke diesel cycle, indirect
injection.
Displacement: 1305 cc (79.6 cubic inches).
Bore: 73.0 mm (2.874 inches).
Stroke: 78.0 mm (3.071 inches).
Compression ratio: 22:1-23:1.
Rated power output: 28 Hp (20.6 kW) at 2700 rpm.
Maximum torque output: 52 lb-ft (70 Nm) at 1800-2000 rpm.
Firing order: 1-3-4-2.
Engine orientation: Variable; configured for transverse or longitudinal
installation based on host machine. Aspiration: Naturally aspirated.
Fuel type: Diesel fuel.
Recommended oil grade: SAE 10W-30 or 15W-40, meeting API CD or higher
specifications.
Oil capacity: 4.2 liters (4.4 U.S. quarts).
Coolant capacity: 5.0 liters (5.3 U.S. quarts) including radiator.
The cylinder block is a monobloc casting from grey cast iron. This
material selection provides high structural rigidity, effective
vibration damping, and excellent wear characteristics. The block
incorporates four cylinder bores, cast integrally. The crankshaft is
supported by five main bearings. This five-bearing design ensures
superior crankshaft support and reduces main bearing loads, contributing
to smooth operation and extended bearing life.
The crankshaft is a forged steel component with integral counterweights.
Main bearing caps are cast iron and secured with two bolts each.
Connecting rods are forged from steel, featuring an I-beam design for
strength. Pistons are aluminum alloy, with a crown contour designed for
compatibility with the indirect injection swirl chamber. Each piston is
fitted with three rings: two compression rings and one oil control ring.
The block includes comprehensive water jackets surrounding each
cylinder.
The cylinder head is a cast iron unit. It employs an overhead valve
(OHV) layout, with the camshaft situated in the cylinder block. The
camshaft is driven by helical gears from the crankshaft, ensuring
precise and quiet timing. Valve actuation is via a direct mechanical
train: camshaft lobe, cylindrical tappet, pushrod, rocker arm, and
valve. The engine uses two valves per cylinder (eight valves total).
Valve clearance is adjusted manually via a screw and locknut on each
rocker arm. Periodic adjustment is a required maintenance procedure to
ensure optimal performance and prevent valve train damage. The cylinder
head incorporates a swirl (pre-combustion) chamber for each cylinder.
This chamber, connected to the main chamber by a restricted passage,
generates intense air swirl during compression to promote efficient
mixing of fuel and air upon injection.
The fuel system is an indirect injection setup utilizing a mechanical,
distributor-type injection pump. This pump, often a Bosch or Zexel
(Diesel Kiki) model, is gear-driven from the engine's camshaft or
auxiliary drive. It contains a single pumping element and a rotary
distributor that delivers high-pressure fuel sequentially to each
injector through individual steel lines. The injectors are pintle-type
and are threaded into the swirl chamber in the cylinder head.
A mechanical lift pump, mounted on the engine block, transfers fuel from
the tank to the injection pump. The system incorporates an integral
mechanical centrifugal governor to control maximum engine speed and
maintain a stable idle. A manual priming pump is fitted for bleeding air
from the system. Fuel filtration is provided by a primary
sedimentor/water separator and a replaceable paper secondary filter.
The lubrication system is a pressure-fed, full-flow filtration wet-sump
design. A trochoid-type (internal gear) oil pump is driven directly by
the crankshaft. Oil is drawn from the sump through a pickup tube and
strainer screen. The oil is pressurized and forced through a full-flow,
spin-on cartridge oil filter. From the filter housing, oil enters the
main gallery in the cylinder block.
It supplies the crankshaft's five main bearings and connecting rod
bearings via drilled passages. A separate drilled passage feeds oil to
the cylinder head to lubricate the rocker arm shaft, rocker arms, and
valve stems. The camshaft bearings in the block are lubricated from the
main gallery. A pressure relief valve maintains system pressure within a
specified range. Oil pressure is monitored by a mechanical gauge or a
warning light sender.
The cooling system is a pressurized, forced-circulation system. A
centrifugal water pump is belt-driven from the crankshaft pulley.
Coolant circulation is regulated by a wax-pellet thermostat housed in a
casting on the cylinder head or front engine cover.
The system uses a tube-and-fin radiator. Cooling is assisted by a
belt-driven fan with a shroud to improve airflow efficiency. A pressure
cap on the radiator maintains system pressure to elevate the coolant's
boiling point.
The air intake system employs a dry, replaceable paper air filter
element, often housed in a remote canister. The engine is equipped with
a mechanical decompression device. This mechanism, actuated by a cable
or lever, holds the exhaust valves slightly open to reduce compression
resistance for easier starting. A 12-volt electric starter motor and an
alternator are standard equipment.
The external dimensions of the K4D engine are compact, designed to fit
within the confined engine compartments of compact loaders and
excavators. Approximate length is 650 mm (25.59 inches). Approximate
width is 550 mm (21.65 inches). Approximate height is 700 mm (27.56
inches). These dimensions include standard ancillaries such as the
injection pump, starter, and alternator, but exclude machine-specific
mounting brackets and hydraulic drives. The dry weight of the K4D engine
is approximately 130-140 kg (287-309 lbs), varying with specific
accessory configurations.
Engine oil and filter changes are required every 100-150 operating hours
or every 3 months under industrial service conditions. The fuel filter
element must be replaced every 200-250 operating hours. Air filter
service is critical; the element should be checked, cleaned, or replaced
every 100 hours in normal conditions, and more frequently in extremely
dusty environments. Valve clearance inspection and adjustment is a
mandatory procedure every 500 operating hours.
Coolant should be drained, flushed, and refilled annually. Fan belt
tension must be checked and adjusted every 100 hours. Fuel injection
timing and injector spray pattern/opening pressure should be verified
every 1000 operating hours. All grease fittings on throttle, governor,
and decompression linkages require periodic lubrication according to the
machine's schedule.
Torque values are specified for clean, dry threads. Cylinder head bolts
are tightened in a specific crisscross sequence to 7.5-8.0 kgm (54-58
lb-ft / 74-78 Nm). Main bearing cap bolts: 6.5-7.0 kgm (47-51 lb-ft /
64-69 Nm). Connecting rod cap bolts: 5.0-5.5 kgm (36-40 lb-ft / 49-54
Nm). Crankshaft pulley bolt: 13.0-14.0 kgm (94-101 lb-ft / 127-137 Nm).
Fuel injection pump mounting bolts: 2.5-3.0 kgm (18-22 lb-ft / 25-29
Nm). Rocker arm shaft bracket bolts: 2.5-3.0 kgm (18-22 lb-ft / 25-29
Nm). Oil drain plug: 4.0-4.5 kgm (29-33 lb-ft / 39-44 Nm). Injector
holder clamp nut: 6.0-6.5 kgm (43-47 lb-ft / 59-64 Nm). Exhaust manifold
nuts: 3.0-3.5 kgm (22-25 lb-ft / 29-34 Nm).
The Mitsubishi K4D engine was primarily used as a power unit for compact
construction and agricultural machinery from the 1980s and 1990s.
Specific machine applications include: Mitsubishi WS706 compact wheel
loader. Weidemann 1705 D/M telescopic handlers/loaders. Pel-Job EB 28.4
and Hanix model SandB 300 mini-excavators. Mitsubishi MT2001, MT2001X,
and MT2201 tractors. It may also be found in other branded equipment
that sourced Mitsubishi industrial engines during this period.
The engine's compact size, four-cylinder smoothness, and reliable 28 Hp
output made it a suitable and common choice for a generation of small,
versatile utility machines. Production has long ceased, but the engine
remains supported by an aftermarket parts network for maintenance of
legacy equipment.
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