Mitsubishi K3C Specifications
| Engine Model: Mitsubishi K3C |
| Engine Type: 4-cycle inline 3-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 54.9 cu.in (0.9 L) |
| Rated Engine Power: 18.5 Hp (13.6 kW) at 2700 rpm |
| Fuel System Type: Indirect fuel injection |
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The Mitsubishi K3C engine is a compact,
three-cylinder, four-stroke diesel powerplant engineered for small
agricultural and industrial machinery. This engine is designed for
durability, fuel efficiency, and reliable operation in demanding
conditions such as those encountered in compact tractors. It features a
water-cooled design, a swirl chamber (indirect) combustion system, and a
forced lubrication system.
The K3C is constructed with a cast iron cylinder block and cylinder
head, providing robustness and effective heat dissipation. Known for its
characteristic three-cylinder sound and strong low-speed torque, this
engine serves as a dependable power source for light-duty tractors and
similar equipment, where simplicity and longevity are prioritized over
high power output. Its design facilitates easy maintenance and service
in field conditions.
Engine family: Mitsubishi K3 series.
Engine type: Inline-three cylinder, four-stroke diesel cycle, indirect
injection.
Displacement: 900 cc (54.9 cubic inches).
Bore: 70.0 mm (2.756 inches).
Stroke: 78.0 mm (3.071 inches).
Compression ratio: 23:1.
Rated power output: 18.5 Hp (13.6 kW) at 2700 rpm.
Maximum torque output: 37.6 lb-ft (51 Nm) at 1900 rpm.
Firing order: 1-2-3.
Engine orientation: Longitudinal.
Aspiration: Naturally aspirated.
Fuel type: Diesel fuel.
Recommended oil grade: SAE 10W-30 or 15W-40, meeting API CD or higher
specifications.
Oil capacity: 3.0 liters (3.2 U.S. quarts).
Coolant capacity: 3.5 liters (3.7 U.S. quarts) including radiator.
The cylinder block is a single, rigid casting from grey cast iron. Its
design provides inherent strength and effective vibration damping for
the three-cylinder layout. The block incorporates three cylinder bores,
cast integrally. The crankshaft is supported by four main bearings, a
configuration that ensures stable crankshaft operation. The crankshaft
is a forged steel component with counterweights to balance the inherent
rocking couple of a three-cylinder engine.
Main bearing caps are cast iron and secured with two bolts each.
Connecting rods are forged from steel. Pistons are aluminum alloy,
featuring a specific crown shape compatible with the swirl chamber
combustion system. Each piston is fitted with three rings: two
compression rings and one oil control ring. The block features deep
water jackets surrounding the cylinders.
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 gear-driven from the crankshaft. Valve actuation follows the
sequence: camshaft lobe, tappet, pushrod, and rocker arm. The engine
uses two valves per cylinder (one intake, one exhaust). Valve clearance
is adjusted via a screw and locknut on the rocker arm, requiring
periodic manual setting.
A key feature is the incorporation of a swirl (pre-combustion) chamber
for each cylinder. This auxiliary chamber, located in the cylinder head,
is connected to the main combustion chamber by a narrow throat. During
compression, air is forced into this chamber, creating intense swirl for
improved air-fuel mixing upon injection.
The fuel system is an indirect injection setup using a distributor-type
fuel injection pump. The pump is a mechanical, rotary distributor unit
(often a Bosch or Mitsubishi design) driven by the engine's gear train.
It meters and pressurizes fuel, delivering it sequentially to each
cylinder's injector via high-pressure steel lines. The injectors are
pintle-type and are mounted in the swirl chamber within the cylinder
head.
A mechanical lift pump transfers fuel from the tank to the injection
pump. A manual primer lever is incorporated for bleeding air from the
system. The system includes a mechanical governor, integrated into the
injection pump, to control maximum engine speed and maintain a stable
idle. Fuel filtration is provided by a primary sedimentor and a
replaceable paper filter element.
The lubrication system is a pressure-fed, full-flow filtration wet-sump
design. A trochoid-type (gear) oil pump is driven by the crankshaft. Oil
is drawn from the sump through a pickup screen. The oil is pressurized
and forced through a full-flow, replaceable cartridge-type oil filter.
From the filter, oil enters the main gallery in the cylinder block.
It supplies the crankshaft's four main bearings and connecting rod
bearings via drilled passages. A separate passage feeds oil to the
cylinder head to lubricate the rocker arm shaft and valve gear. The
camshaft bearings in the block are lubricated from the main gallery. Oil
pressure is monitored by a mechanical gauge or warning light sender. The
system includes a pressure relief valve.
The cooling system is a pressurized, pump-circulated thermosiphon
system. A centrifugal water pump is driven by a V-belt from the
crankshaft pulley. Coolant circulates through the block and head,
exiting to a tube-and-fin radiator.
A bellows-type thermostat regulates coolant flow to maintain operating
temperature. The system employs a radiator pressure cap to raise the
coolant's boiling point. Cooling is assisted by a belt-driven fan.
The air intake system uses a dry, replaceable paper air filter. The
engine is equipped with a mechanical decompression device, operated by a
lever or cable, which holds the exhaust valves slightly open to reduce
compression for easier manual starting. The electrical system includes a
12-volt starter motor and an alternator.
The external dimensions of the K3C engine are compact, suitable for
installation in small machinery. Approximate length is 550 mm (21.65
inches). Approximate width is 450 mm (17.72 inches). Approximate height
is 650 mm (25.59 inches). These dimensions include the radiator fan,
injection pump, and starter motor. The dry weight of the engine, as
specified, is 125 kg (276 lbs). This mass is consistent with its
all-iron construction.
Engine oil and filter changes are required every 100 operating hours or
every 6 months. The fuel filter and air filter elements require
replacement every 200-300 operating hours, or more frequently in dusty
conditions. Valve clearance inspection and adjustment is a critical
service task, required every 500 operating hours. The coolant should be
drained, flushed, and refilled annually.
The water pump drive belt tension should be checked and adjusted every
100 hours. The injection pump timing and injector opening pressure
should be verified every 1000 operating hours. The compression release
mechanism should be lubricated and checked for proper operation
periodically. All grease points on the external linkage should be
serviced according to the machine's manual.
Torque values are for clean, dry threads. Cylinder head bolts are
tightened in a specific crisscross sequence to 7.0-7.5 kgm (51-54 lb-ft
/ 69-74 Nm). Main bearing cap bolts: 6.0-6.5 kgm (43-47 lb-ft / 59-64
Nm). Connecting rod cap bolts: 5.0-5.5 kgm (36-40 lb-ft / 49-54 Nm).
Crankshaft pulley bolt: 12.0-13.0 kgm (87-94 lb-ft / 118-127 Nm). Fuel
injection pump mounting bolts: 2.0-2.5 kgm (14-18 lb-ft / 20-25 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).
The Mitsubishi K3C engine is primarily found in compact agricultural
tractors, most notably those manufactured by Iseki. Its main
applications are in the following tractor models: Iseki TU150. Iseki
TU157. Iseki TU160. Iseki TU1600. It may also be found in other light
industrial machinery such as small generators, pumps, or construction
equipment that utilizes a compact, reliable diesel engine in this power
range.
The engine's use is specific to machinery where its particular
combination of compact size, three-cylinder configuration, and
industrial durability are required. Production of this specific engine
has ceased, but it remains in service in many older machines.
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