Mitsubishi K3A Specifications
| Engine Model: Mitsubishi K3A |
| Engine Type: 4-cycle inline 3-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 46.7 cu.in (0.77 L) |
| Rated Engine Power: 16.5 Hp (12.3 kW) at 2600 rpm |
| Fuel System Type: Indirect injection |
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The Mitsubishi K3A is a compact, vertical,
water-cooled three-cylinder diesel engine from the K-Series family,
designed for small agricultural tractors, construction machinery, and
industrial generator sets. Introduced in the late 1970s, the K3A became
a popular choice for sub-compact and compact tractors, particularly in
Iseki models such as the TX1410, TX2140, and TU1400, as well as the
Mitsubishi MT160 and Bolens H2502. Its reputation for reliability, fuel
efficiency, and ease of service established it as a benchmark in the
under-20 horsepower diesel segment.
The Mitsubishi K3A is characterized by its indirect injection combustion
system with a swirl chamber - a design that provides smooth operation,
reduced combustion noise, and good cold-start performance. The engine
uses a Bosch M-type in-line injection pump, a cast iron cylinder block
and cylinder head, and a forged steel crankshaft with three main
bearings. The naturally aspirated configuration eliminates turbocharger
complexity. The engine's compact dimensions and low weight make it
suitable for space-constrained engine compartments in compact tractors
and industrial equipment.
The Mitsubishi K3A is a four-stroke, water-cooled, naturally aspirated
inline-three diesel engine configured for longitudinal mounting in
rear-wheel-drive agricultural and industrial applications.
Engine Type: Inline-3, 4-cycle, water-cooled, naturally aspirated diesel
Displacement: 766 cc (46.7 cu.in)
Bore and Stroke: 65.0 mm (2.56 in) x 78.0 mm (3.07 in)
Compression Ratio: 23.0:1
Valvetrain: OHV, 6-valve (2 valves per cylinder)
Combustion System: Indirect injection (IDI) with swirl chamber
Fuel System: Mechanical direct injection (in-line pump)
Injection Pump: Bosch M-type in-line pump
Firing Order: 1-3-2
Lubrication: Forced lubrication via trochoid pump
Electrical System: 12V with 1.6 kW starter motor
Maximum Power: 12.0-12.3 kW (16.0-16.5 hp) at rated speed
Rated Speed: 2,200-2,600 rpm depending on application
The cylinder block is manufactured from high-strength gray cast iron
using a deep-skirt design, providing structural rigidity under diesel
operation. The block features a closed-deck configuration, ensuring the
cylinder bores are fully supported by the water jacket structure.
Cast-in-place cylinder bores are machined directly into the iron
casting. The block incorporates three main bearing webs - one between
each cylinder and one at each end - with two-bolt main bearing caps. A
stamped steel oil pan is bolted to the lower crankcase.
Block Material: Cast iron
Bore Diameter: 65.0 mm (2.56 in)
Main Bearing Caps: Cast iron, two-bolt design
Crankshaft: Forged steel crankshaft with three main bearings.
Connecting Rods: Forged steel.
Pistons: Cast aluminum alloy.
The cylinder head is constructed from cast iron, matching the thermal
expansion characteristics of the block. The head utilizes an indirect
injection combustion system with individual swirl chambers -
pre-combustion chambers - for each cylinder, formed by steel inserts
pressed into the cylinder head. These chambers provide turbulent mixing
for smooth, quiet diesel operation.
The OHV valvetrain operates six valves - two per cylinder - via pushrods
and rocker arms. Valve clearance is set manually using adjustment screws
on the rocker arms, a system requiring periodic maintenance.
Head Material: Cast iron
Combustion Chamber Type: Indirect injection with steel swirl chamber
inserts
Valve Configuration: OHV, 2 valves per cylinder with pushrods and rocker
arms
Valve Clearance (Cold, Intake): 0.25 mm (0.010 in)
Valve Clearance (Cold, Exhaust): 0.25 mm (0.010 in)
The Mitsubishi K3A employs a mechanical indirect injection fuel system
with a Bosch M-type in-line injection pump. The injection pump is
mounted on the side of the cylinder block and driven by the engine’s
gear train. The pump uses individual plungers for each cylinder,
delivering precisely metered fuel through high-pressure steel injection
lines.
Nozzle-type injectors are mounted in the cylinder head, each spraying
fuel into the swirl chamber. A mechanical governor regulates fuel
delivery based on engine speed and load. A manual primer pump is
integrated into the fuel system to facilitate bleeding air.
Injection Type: Mechanical indirect injection
Injection Pump: Bosch M-type in-line pump
Injection Timing: Generally 16-18 degrees before top dead center
Fuel Requirement: Diesel fuel with minimum cetane number of 45
Fuel Filter: Replaceable cartridge type with water separator
The lubrication system is a fully pressurized, wet-sump design utilizing
a trochoid-type oil pump mounted to the front of the crankshaft. The oil
pump draws lubricant from a stamped steel oil pan through a mesh
strainer and circulates it through a full-flow, replaceable oil filter.
From the gallery, pressurized oil is distributed to the crankshaft main
bearings, connecting rod bearings, and camshaft bearings. A pressure
relief valve maintains system pressure within operational limits.
Oil Type: Diesel-rated SAE 10W-30, 15W-40, or 20W-50 (API CC, CD, or
higher)
Oil Capacity: 1.8-3.0 liters (1.9-3.2 US qt), depending on oil pan
configuration
Oil Pressure (at rated speed): 294-392 kPa (42.6-56.9 psi)
Oil Pump Type: Trochoid-type, crankshaft-driven
The cooling system is a pressurized, liquid-cooled design with a
cross-flow radiator with a mechanical fan. A centrifugal-type water pump
circulates coolant through the cylinder block and cylinder head. A
wax-pellet thermostat regulates coolant flow.
Coolant Type: Ethylene-glycol based antifreeze with corrosion inhibitors
Coolant Capacity (engine only): 3.0 liters (3.2 US qt)
Thermostat Opening Temperature: 76-82 °C (169-180 °F)
Water Pump Type: Centrifugal, belt-driven
Intake System: Naturally aspirated; air passes through a dry-type air
filter.
Exhaust System: Cast iron exhaust manifold.
Timing Drive: Precision-cut gears drive the camshaft and injection pump
from the crankshaft.
Overall Length: 550 mm (21.7 in)
Overall Width: 450 mm (17.7 in)
Overall Height: 600 mm (23.6 in)
Dry Weight (complete engine): 85 kg (187 lb)
Oil Change Interval: 100-150 hours of operation.
Oil Filter Change: At every oil change.
Engine Coolant Replacement: 500 hours or 2 years.
Fuel Filter Replacement: 200 hours or as indicated by water separator
inspection.
Valve Clearance Adjustment: Inspect and adjust every 500 hours.
Valve Clearance (Intake): 0.25 mm (0.010 in) cold.
Valve Clearance (Exhaust): 0.25 mm (0.010 in) cold.
Air Filter Maintenance: Every 100 hours.
Cylinder Head Bolts (M10): 73.5-83.4 Nm (54.2-61.5 lb-ft).
Main Bearing Cap Bolts: 49.0-53.9 Nm (36.1-39.8 lb-ft).
Connecting Rod Cap Nuts: 31.4-34.3 Nm (23.1-25.3 lb-ft).
Agricultural Tractors: Iseki TX1410, TX1510, TX2140, TU1400; Mitsubishi
MT160; Bolens H2502.
Industrial Applications: Small generators, irrigation pumps, mini
excavators, compact loaders.
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