Mitsubishi K3F Specifications
| Engine Model: Mitsubishi K3F |
| Engine Type: 4-cycle inline 3-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 72.3 cu.in (1.18 L) |
| Rated Engine Power: 24 Hp (18 kW) at 2600 rpm |
| Fuel System Type: Indirect injection |
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The Mitsubishi K3F is a vertical, water-cooled,
4-stroke, 3-cylinder diesel engine with a displacement of 1.184 liters.
This compact power unit belongs to the Mitsubishi K-series engine
family, widely used in agricultural and construction machinery from the
1980s through the early 2000s.
The engine employs a swirl chamber indirect injection (IDI) combustion
system, which produces smooth operation and reduced combustion noise at
low engine speeds. Its compact dimensions allow installation in mini
excavators such as the Hitachi UE 25 and compact tractors including the
Deutz-Fahr Agrokid 25. The naturally aspirated design eliminates
turbocharger complexity, while the replaceable dry cylinder liner system
permits cost-effective rebuilding.
The Mitsubishi K3F shares its bore and stroke dimensions with the
4-cylinder K4F engine, offering parts commonality across the K-series
family. This engine preceded the electronically managed K3G and K3M
series, providing a mechanical fuel system serviceable with basic tools
in remote field conditions.
Engine Type: Vertical, in-line 3-cylinder, 4-stroke, water-cooled diesel
Displacement: 1184 cc (1.184 L / 72.3 cu.in)
Bore x Stroke: 84 mm x 72 mm (3.31 in x 2.83 in)
Compression Ratio: 22.0:1
Combustion System: Swirl chamber (indirect injection, IDI)
Aspiration: Naturally aspirated
Firing Order: 1-3-2
Rotation (from flywheel end): Counter-clockwise
Maximum Power (continuous): 15-18 kW (20-24 hp) at 2600 rpm
Maximum Torque: 72 Nm (53 lb-ft) at 1800 rpm
Low Idle Speed: 800-850 rpm
High Idle Speed (no-load, governed): 2900 rpm
Compression Pressure (standard): 4.20 MPa (610 psi) at 280 rpm
Compression Pressure (service limit): 3.15 MPa (457 psi) at 280 rpm
Emission Standard: Pre-regulation (Tier 0 equivalent)
The cylinder block is manufactured from cast iron with an open-deck
design. Three cylinder bores are machined directly into the parent
metal. The block employs replaceable dry cylinder liners pressed into
the bores. Each liner is a centrifugally cast alloy iron tube with a
hardened internal bore surface. The dry liner design transfers heat
through full contact between the liner outer wall and the block casting.
The block features a siamese bore configuration where each cylinder
shares a common wall with the adjacent cylinder, reducing overall engine
length. The crankcase extends below the crankshaft centerline. Four main
bearing bulkheads support the crankshaft, with thrust bearing position
at the rear main journal. The water jacket surrounds the upper 60% of
each cylinder liner.
Cast oil galleries supply lubricant to the main bearings and camshaft
bearings. A side-mounted cartridge-type oil filter threads directly onto
the block casting. Cylinder Liners: Replaceable dry type (parent bore
liners). Liners are pressed into the block and require a special puller
for removal. Liner protrusion above the block deck is 0.03-0.10 mm
(0.001-0.004 in).
The cylinder head is a single-piece cast iron component with a swirl
chamber for each cylinder. Each swirl chamber is a spherical
pre-combustion chamber located off-center within the combustion bowl.
Glow plugs are threaded into each swirl chamber for cold start
assistance. The valve train is an overhead valve (OHV) configuration
with pushrods and rocker arms. Each cylinder receives two valves: one
intake and one exhaust, arranged in a parallel valve layout.
Valve stem seals are positive-type on intake valves only. Hardened valve
seat inserts on the exhaust side resist wear under elevated
temperatures. The camshaft is located in the cylinder block, not the
cylinder head. Valve clearance adjustment uses a screw-and-locknut
arrangement on the rocker arms. The cold clearance specification for
both intake and exhaust valves is 0.25 mm (0.010 in). The rocker shaft
is supported by three pedestals bolted directly to the cylinder head.
The fuel system is a mechanical indirect injection design. A Bosch
M-type in-line injection pump mounts to the side of the timing gear
case. This pump is a distributor type with a single plunger delivering
fuel to each cylinder in the 1-3-2 firing order. The injection pump
incorporates a mechanical centrifugal governor with both idle and
maximum speed control springs. A manual stop lever permits mechanical
fuel shutoff.
Steel injection lines route individually to each injection nozzle
located in the swirl chamber. Injection nozzles are throttle-type
(pintle) with an opening pressure of 9.8-10.3 MPa (1420-1495 psi).
Injection timing is set at 21 degrees before top dead center (BTDC) as
measured by the fuel spill method. A hand primer lever on the feed pump
permits manual bleeding of air. A fuel filter with an integral water
sediment bowl mounts on the engine side of the block.
The lubrication system uses a trochoid-type oil pump driven directly
from the crankshaft gear. The trochoid pump consists of an inner rotor
with four lobes and an outer rotor with five lobes, providing smooth
flow with minimal pulsation. The pump draws oil through a wire mesh
suction strainer positioned at the bottom of the oil pan. Oil passes
through a spin-on or cartridge-type full-flow filter mounted on the left
side of the cylinder block. A pressure relief valve in the oil pump
housing opens at 0.49-0.54 MPa (71-78 psi) to prevent
over-pressurization during cold starts.
The system lacks piston cooling jets due to the indirect injection
combustion system generating lower thermal loads. Oil pressure at rated
speed measures 0.29-0.39 MPa (42-57 psi). A low oil pressure switch
activates a warning lamp at 0.05 MPa (7 psi). Standard oil pan capacity
is 4.0 L (4.2 qt). A deep sump option increases capacity to 5.2 L (5.5
qt) for applications operating on inclines.
The cooling system is pressurized and water-cooled, driven by a
belt-mounted centrifugal water pump. Coolant flows from the radiator
lower hose into the water pump, then through the cylinder block water
jacket surrounding the dry liners, upward through the cylinder head, and
returns to the radiator top tank. A wax-pellet thermostat, mounted in a
housing on the cylinder head, begins opening at 76.5°C (170°F) and
achieves full opening at 90°C (194°F).
A bypass circuit permits coolant circulation within the engine when the
thermostat remains closed. Coolant capacity for the engine block and
cylinder head only is 3.0 L (3.2 qt). Total system capacity, including
radiator and hoses, ranges from 4.5 to 5.5 L (4.8-5.8 qt) depending on
the installation. A removable pressure cap relieves excess pressure at
0.9 bar (13 psi). A four-blade fan mounted to the water pump pulley
draws air through the radiator core.
Aspiration: Natural aspiration without turbocharger. Air passes through
a dry-type paper filter element with a foam pre-cleaner. An intake
silencer reduces induction noise.
Combustion System: Indirect injection using a swirl chamber. The chamber
volume occupies 55% of the total clearance volume. A glow plug heats the
chamber for cold start assistance down to -15°C (5°F).
Electrical System: 12 V negative ground. Starter motor power rating is
1.6 kW. Alternator output is 35 A. Glow plugs operate at 12 V with a
maximum current of 7 A per plug. A glow timer relay provides 5-10 second
pre-heat dependent on coolant temperature.
Starting Aid: Glow plugs in each swirl chamber. The system includes a
thermistor-equipped timer relay that modulates post-heat duration (up to
20 seconds) to reduce white smoke after start.
Governor: Mechanical centrifugal governor integral to the injection
pump. Governor droop is 8-12% from no-load to full-load at rated speed.
Length (fan to flywheel housing): 524 mm (20.63 in)
Width (overall, exhaust manifold to injection pump): 460 mm (18.11 in)
Height (oil pan rail to rocker cover): 580 mm (22.83 in)
Dry Weight (basic engine, no flywheel, no starter, no alternator): 110
kg (243 lb)
Dry Weight (open power unit with radiator, flywheel, starter,
alternator): 145 kg (320 lb)
Oil Pan Depth (standard sump): 85 mm (3.35 in) from block rail
Engine Oil Change Interval: 250 hours or 6 months under normal
industrial duty.
Engine Oil Capacity (standard pan, including filter): 4.0 L (4.2 qt)
Engine Oil Capacity (deep sump, including filter): 5.2 L (5.5 qt)
Engine Oil Grade (ambient above -5C / 23F): SAE 15W-40 or SAE 20W-50,
API CC or CD.
Engine Oil Grade (cold ambient -15C to 5C / 5F to 41F): SAE 10W-30.
Engine Oil Grade (extremely cold below -15C / 5F): SAE 5W-20.
Engine Oil Pressure at Rated Speed: 0.29-0.39 MPa (42-57 psi)
Engine Oil Pressure at Low Idle (minimum, hot engine): 0.07 MPa (10 psi)
Coolant Capacity (engine only): 3.0 L (3.2 qt)
Coolant Capacity (system total): 4.5-5.5 L (4.8-5.8 qt)
Coolant Specification: Ethylene glycol base antifreeze with low-silicate
formulation.
Thermostat Opening Temperature: 76.5C (170F) start; fully open at 90C
(194F)
Fuel Filter Replacement Interval: 200 hours. Water sediment bowl drain
daily.
Air Filter Service Interval: Clean foam pre-cleaner every 50 hours.
Air Filter Service Interval: Replace paper element every 200 hours.
Valve Clearance (Cold, Intake and Exhaust): 0.25 mm (0.010 in).
Valve Clearance Inspection Interval: 250 hours.
Injection Timing (static, fuel spill method): 21 degrees BTDC at No. 1
cylinder.
Injector Nozzle Opening Pressure: 9.8-10.3 MPa (1420-1495 psi)
Injector Nozzle Replacement Interval: 1000 hours.
Glow Plug Resistance (cold): 1.1-1.3 ohms per plug. Replace if open
circuit or shorted.
Compression Pressure Variation Between Cylinders: Maximum 0.2 MPa (29
psi) difference.
Drive Belt Tension: Deflection of 12-15 mm (0.47-0.59 in) under 10 kg
(22 lb) force at belt midpoint.
Idle Speed Adjustment (low): 800-850 rpm. Adjust via idle stop screw on
injection pump.
Idle Speed Adjustment (high, governed): 2900 rpm no-load. Adjust via
maximum speed screw.
Cylinder Head Bolts (M14, Stage 1): 50 Nm (37 lb-ft)
Cylinder Head Bolts (M14, Stage 2): 110 Nm (81 lb-ft)
Cylinder Head Bolts (M14, Stage 3): 150 Nm (111 lb-ft)
Cylinder Head Bolts (Tappet Side, M10): 110 Nm (81 lb-ft)
Connecting Rod Cap Nuts: 55-60 Nm (40-44 lb-ft)
Main Bearing Cap Bolts: 105 Nm (77 lb-ft)
Flywheel Bolts (to crankshaft flange): 85 Nm (63 lb-ft)
Flywheel Housing Bolts (to block): 45 Nm (33 lb-ft)
Camshaft Thrust Plate Bolts: 15 Nm (11 lb-ft)
Rocker Arm Shaft Bracket Bolts: 35 Nm (26 lb-ft)
Rocker Arm Adjusting Lock Nut: 12 Nm (9 lb-ft)
Valve Cover Nuts (with cork gasket): 8 Nm (6 lb-ft)
Injection Pump Mounting Nuts (to timing case): 35 Nm (26 lb-ft)
Injection Pump Drive Gear Nut: 55 Nm (41 lb-ft)
Injection Line Fittings (pump end): 22 Nm (16 lb-ft)
Injection Line Fittings (nozzle end): 22 Nm (16 lb-ft)
Injector Hold-Down Clamp Nut: 25 Nm (18 lb-ft)
Crankshaft Pulley Bolt: 100 Nm (74 lb-ft)
Oil Pan Bolts (M8): 12 Nm (9 lb-ft)
Oil Pan Drain Plug: 40 Nm (30 lb-ft)
Oil Filter (spin-on canister): Hand tighten plus 3/4 turn, or 12 Nm (9
lb-ft)
Water Pump Mounting Bolts: 20 Nm (15 lb-ft)
Thermostat Housing Bolts: 12 Nm (9 lb-ft)
Starter Motor Mounting Bolts (12V, 1.6 kW): 45 Nm (33 lb-ft)
Alternator Mounting Bolt (pivot): 35 Nm (26 lb-ft)
Alternator Adjustment Arm Bolt: 20 Nm (15 lb-ft)
Glow Plug (in cylinder head): 20 Nm (15 lb-ft)
Exhaust Manifold Nut: 25 Nm (18 lb-ft)
Intake Manifold Bolt: 20 Nm (15 lb-ft)
Engine Mount Bracket Bolts (to block): 60 Nm (44 lb-ft)
Mini Excavators: Hitachi UE 25, UE 30. IHI 15J, IHI 20J, IHI 25J. Yanmar
B15, B20 (licensed installations). Kubota KH-25, KH-30 with Mitsubishi
engine packages. Furukawa EX25, EX30.
Compact Tractors: Deutz-Fahr Agrokid 25, Agrokid 30. Mitsubishi D20,
D25, D30 series. Satoh Beaver S370, S470. Iseki T250, T260. Kubota B26,
B27 (selected markets with K3F supply agreement).
Agricultural Equipment: Small rice transplanters (Mitsubishi LK series).
Compact irrigation pumps (50-80 mm suction diameter). Walk-behind
tractors (power tillers) in Asian markets. Small forage harvesters.
Stationary Generator Sets: 8-15 kVA single-phase and three-phase
generators. Standby power ratings from 10 kW to 14 kW at 1500 rpm (50
Hz) or 1800 rpm (60 Hz). Models include Denyo DCA-12, MQ Power GA-12,
Mecc Alte alternator packages.
Industrial Power Units: Hydraulic power packs for small presses and lift
platforms. Wood chippers (drum diameter 200-300 mm). Concrete vibrator
drives. Small compaction plates (forward plate).
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