Mitsubishi K3M Specifications
| Engine Model: Mitsubishi K3M |
| Engine Type: 4-cycle inline 3-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 91.3 cu.in (1.49 L) |
| Rated Engine Power: 30 Hp (22 kW) at 3000 rpm |
| Fuel System Type: Indirect injection |
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The Mitsubishi K3M is a vertical, water-cooled,
4-stroke, 3-cylinder diesel engine with a displacement of 1.496 liters.
This engine belongs to the K-series family, positioned between smaller
K3 variants and larger displacement models. The K3M is extensively used
in mid-sized compact tractors and mini-excavators, valued for its higher
power output compared to smaller K3 series engines while maintaining a
relatively compact footprint for installation in space-constrained
engine bays.
The engine employs indirect injection (IDI) combustion using a swirl
chamber system. This design delivers smoother operation and lower noise
compared to direct injection engines of similar size, an advantage for
operator comfort in agricultural and construction applications. The
Mitsubishi K3M features a cast iron cylinder block, an aluminum alloy
cylinder head, and a mechanical fuel injection system calibrated for
industrial duty cycles.
Operators and equipment owners value this engine for its reliable cold
starting, fuel efficiency, and the availability of service parts across
Mitsubishi's global dealer network. The engine appears in tractors from
multiple brands including Mitsubishi MT300, Mahindra 3015, and Case IH
models, as well as in 3-ton class Japanese mini-excavators.
Engine Type: Vertical, water-cooled, 4-stroke, 3-cylinder diesel.
Number of Cylinders: 3 (in-line).
Bore: 84.0 mm (3.31 in).
Stroke: 90.0 mm (3.54 in).
Total Displacement: 1.496 L (1,496 cc / 91.3 cu.in).
Compression Ratio: 23.0:1.
Combustion System: Indirect injection (swirl chamber or pre-combustion
chamber).
Firing Order: 1-3-2.
Rotation (viewed from flywheel end): Clockwise.
Horsepower Output: 20-22 kW (27-30 hp) at 2,600-3,000 rpm.
Compression Pressure (std): 30 kg/cm2 (427 psi) at 280 rpm cranking
speed.
Compression Pressure (service limit): 22 kg/cm2 (313 psi) at 280 rpm.
Idle Speed: 800-900 rpm.
Rated Speed (tractor applications): 2,600-2,800 rpm.
Rated Speed (excavator applications): 2,400-2,600 rpm.
The cylinder block of the K3M is manufactured from high-grade cast iron
with a vertical 3-cylinder inline configuration. This material choice
provides high rigidity, excellent vibration damping, and resistance to
wear in the harsh operating environments of agricultural and
construction equipment. The block design incorporates a deep-skirt
crankcase, where the cylinder walls extend below the crankshaft
centerline, adding structural support for the rotating assembly.
The cylinder bores are machined directly into the parent cast iron
material; the Mitsubishi K3M does not use replaceable cylinder liners.
Bore surfaces are induction-hardened to improve wear resistance and
plateau-honed to optimize oil retention for piston ring sealing. The
block houses a four-main-bearing crankshaft (one main bearing between
each cylinder, plus front and rear units). Each main bearing cap is
secured by two bolts.
The crankcase is designed with an integrated oil pan rail, providing a
flat sealing surface for the pressed steel oil pan. The block contains
the mounting pad for the fuel injection pump, driven by a gear train at
the front of the engine. Coolant passages within the block direct water
flow from the water pump inlet upward toward the cylinder head. The left
side of the block carries the oil filter assembly and the fuel feed
pump. The right side provides the mounting points for the starter motor.
The cylinder head is constructed from cast aluminum alloy, reducing
overall engine weight and improving heat dissipation from the combustion
chambers. The head is a single casting covering all three cylinders,
with a cross-flow design featuring intake ports on one side and exhaust
ports on the opposite side. A defining characteristic of this cylinder
head is the indirect injection (IDI) swirl chamber for each cylinder.
Valvetrain Configuration: Overhead valve (OHV), pushrods, rocker arms.
Valves per Cylinder: 2 (one intake, one exhaust).
Total Valves: 6.
Intake Valve Diameter: 34.0 mm (1.34 in).
Exhaust Valve Diameter: 30.0 mm (1.18 in).
Valve Stem Diameter: 8.0 mm (0.315 in).
Valve Seat Inserts: Hardened steel, pressed into the aluminum head.
Camshaft Position: In-block (camshaft located within the cylinder block,
driven by gears).
Valve Lash Adjustment: Screw and locknut on rocker arms.
The swirl chamber is a spherical cavity cast into the cylinder head,
connected to the main combustion chamber above the piston by a
tangential throat passage. Fuel is injected into this swirl chamber,
where intense air motion created during the compression stroke promotes
thorough air-fuel mixing. Combustion begins in the swirl chamber and
expands into the main chamber, providing quieter operation than direct
injection systems.
The valve train uses pushrods and rocker arms. The camshaft is mounted
within the cylinder block, driven by a gear train from the crankshaft.
Cam lobes actuate mechanical lifters (flat tappets), pushrods travel
upward to rocker arms, and rocker arms press down on the valve stems.
The rocker shaft is supported on three pedestals bolted to the cylinder
head. Valve clearance is adjusted by loosening the rocker arm locknut
and turning the adjusting screw.
Cold Valve Clearance:
Intake Valves: 0.25 mm (0.010 in).
Exhaust Valves: 0.25 mm (0.010 in).
The fuel system is an indirect injection design using a distributor-type
injection pump with a mechanical governor. The system is calibrated for
industrial duty cycles, prioritizing reliability, easy starting, and
consistent operation across varying loads.
Fuel System Type: Indirect injection (IDI) with distributor pump.
Injection Pump Type: Bosch VE-type or Mitsubishi MVP-type rotary
distribution pump.
Injection Pressure (nozzle opening): 120-130 bar (1,740-1,885 psi).
Injection Timing (static): 21° BTDC (before top dead center).
Injector Type: Pencil-type with single-hole or pintle nozzle.
Injector Opening Pressure (new): 120 bar (1,740 psi).
Injector Opening Pressure (service limit): 110 bar (1,595 psi).
Injection Order: 1-3-2.
Fuel Filtration: Primary sedimenter plus secondary spin-on filter.
The Bosch VE or Mitsubishi MVP pump is a single-plunger distributor
pump. A single pumping plunger generates high pressure, and a
distributor rotor directs pressurized fuel to each cylinder's injector
in the correct firing sequence (1-3-2). The pump incorporates a
mechanical governor with idle and maximum speed springs, a cold-start
advance device, and a fuel shut-off solenoid. The pump is mounted to the
cylinder block and driven by a gear from the camshaft or crankshaft.
The combustion system uses a glow plug for each cylinder, providing
cold-start assistance. Glow plugs are pencil-type units with a heating
element protruding into the swirl chamber. A glow plug controller,
activated by the key switch, operates the glow plugs for a pre-heat
period (approximately 5-10 seconds depending on ambient temperature) and
may maintain post-heat after engine start.
The lubrication system is a full-pressure design using a gear-type oil
pump mounted inside the oil pan and driven by the crankshaft. The pump
draws oil through a fixed wire-mesh strainer and pushes it through a
full-flow spin-on oil filter before distribution to the engine's main
oil gallery.
Oil Capacity (including filter): 4.0 L (1.05 U.S. gal / 4.2 qt).
Oil Pressure at Rated Speed (warm): 2.5-3.5 bar (36-51 psi).
Oil Pressure at Idle (warm, minimum): 0.7 bar (10 psi).
Oil Pump Type: Gear-type (external spur gears).
Oil Filter Type: Full-flow, spin-on (M20 x 1.5 thread common).
Recommended Oil Viscosity (ambient above 0°C): 15W-40, API CD, CE, or
CF.
Recommended Oil Viscosity (cold climates): 10W-30 or 5W-30.
Oil Change Interval (normal service): 100-200 hours or annually.
The main oil gallery runs the length of the cylinder block, delivering
oil to the four main bearings. Oil reaches the connecting rod bearings
through drilled passages in the crankshaft. Camshaft bearings and valve
train components (lifters, pushrods, rocker arms) receive oil through
vertical passages from the cylinder block. An oil pressure switch,
located on the cylinder block, activates a warning lamp when pressure
falls below the safe threshold.
The cooling system is a pressurized, water-cooled design using a
belt-driven centrifugal water pump. The system includes a
thermostatically controlled bypass circuit for rapid engine warm-up. A
radiator with an engine-driven fan provides heat rejection.
Coolant Capacity (engine only): 3.5 L (3.7 qt).
Coolant Capacity (with radiator): 5.0-6.0 L (5.3-6.3 qt), dependent on
installation.
Water Pump Type: Centrifugal, belt-driven from crankshaft pulley.
Thermostat Opening Temperature (start): 71°C (160°F).
Thermostat Fully Open Temperature: 85°C (185°F).
Radiator Cap Pressure: 0.9 bar (13 psi).
Recommended Coolant: Ethylene glycol-based, 30-50% concentration.
The cooling system directs coolant from the water pump into the cylinder
block, where it flows around each cylinder bore through vertical
passages. Coolant then enters the cylinder head, flowing across the
combustion deck, swirl chambers, and exhaust valve seats before exiting
through the thermostat housing at the front or rear of the cylinder
head. The bypass circuit allows coolant to circulate within the engine
while the thermostat remains closed, preventing localized hot spots
during warm-up. A coolant temperature sender for the dashboard gauge or
warning lamp is mounted on the thermostat housing.
| Intake and Exhaust Systems |
Air Intake System: Single dry paper air filter, often with a pre-cleaner
on agricultural applications.
Exhaust System: Cast iron exhaust manifold, single vertical outlet
(tractor) or horizontal outlet (excavator).
Electrical System (standard): 12-volt.
Starter Motor: 1.6 kW (2.1 hp) pre-engaged type with integral solenoid.
Alternator: 12V, 35A (420 W) with internal regulator.
Glow Plug System: Three pencil-type glow plugs, manual or automatic
controller with pre-heat and post-heat functions.
Glow Plug Voltage (operating): 10.5-11.5 V.
Glow Plug Resistance (cold): 0.8-1.0 ohms per plug.
Dry Weight (complete engine, no fluids, no flywheel): 130 kg (287 lb).
Dry Weight (with flywheel and exhaust manifold): 142 kg (313 lb).
Length (front pulley to flywheel face): 570 mm (22.4 in).
Width (maximum at injection pump): 490 mm (19.3 in).
Height (oil pan to rocker cover top): 680 mm (26.8 in).
Crankshaft Centerline to Top of Rocker Cover: 285 mm (11.2 in).
Valve Clearance (Cold, Intake and Exhaust): 0.25 mm (0.010 in).
Valve Clearance Inspection Interval: 500 hours.
Engine Oil Change Interval (normal service): 100-200 hours.
Oil Filter Change Interval: Every oil change.
Fuel Filter Change Interval: 200 hours.
Coolant Change Interval: 1,000 hours or 2 years.
Air Filter Service Interval: 100 hours (more in dusty conditions).
Glow Plug Inspection Interval: 500 hours.
Injector Testing Interval: 1,000 hours.
Injection Pump Timing Check Interval: 1,000 hours.
Idle Speed Adjustment: 800-900 rpm.
Maximum No-Load Speed: 3,100 rpm (governor controlled).
Valve Timing Events:
Intake Valve Opens: 8° BTDC
Intake Valve Closes: 32° ABDC
Exhaust Valve Opens: 42° BBDC
Exhaust Valve Closes: 8° ATDC
Cylinder Head Bolts (M14, coarse thread): 147-157 Nm (108.4-115.7
lb-ft).
Cylinder Head Bolts (tappet side, smaller bolts): 98-108 Nm (72.3-79.5
lb-ft).
Connecting Rod Cap Nuts: 54-59 Nm (39.8-43.4 lb-ft).
Main Bearing Cap Bolts: 103 Nm (76 lb-ft).
Flywheel Bolts: 83 Nm (61.5 lb-ft).
Crankshaft Pulley Bolt (front): 118 Nm (87 lb-ft).
Camshaft Drive Gear Bolts: 25 Nm (18 lb-ft).
Injection Pump Drive Gear Bolt: 30 Nm (22 lb-ft).
Intake Manifold Nuts: 18 Nm (13 lb-ft).
Exhaust Manifold Nuts: 22 Nm (16 lb-ft).
Valve Cover Bolts (rocker cover): 7-9 Nm (62-80 lb-in).
Rocker Shaft Bracket Bolts: 25 Nm (18 lb-ft).
Rocker Arm Adjusting Locknut: 15 Nm (11 lb-ft).
Oil Pan Bolts: 10-12 Nm (89-106 lb-in).
Oil Drain Plug: 35 Nm (26 lb-ft).
Starter Motor Mounting Bolts: 35 Nm (26 lb-ft).
Alternator Pivot Bolt: 25 Nm (18 lb-ft).
Glow Plugs (installation, dry): 12 Nm (106 lb-in).
Fuel Injectors (hold-down clamp nuts): 20 Nm (15 lb-ft).
Injector Pipe Flare Nuts: 25 Nm (18 lb-ft).
Water Pump Mounting Bolts: 15 Nm (11 lb-ft).
Thermostat Housing Bolts: 10 Nm (89 lb-in).
Fan Belt Pulley Bolts (water pump): 25 Nm (18 lb-ft).
Engine Mount Bracket Bolts: 50 Nm (37 lb-ft).
Compact Tractors (Mitsubishi Branded): The K3M powers the Mitsubishi
MT300 series (MT300, MT320, MT340), models in the 27-30 hp range. These
tractors serve small farms, equestrian properties, and municipal grounds
maintenance.
Compact Tractors (Rebranded, Agricultural): The engine is installed in
the Mahindra 3015, a 30-hp compact utility tractor widely sold in North
American and Asian markets. Case IH models including the 275 (compact
utility) and the 1140 (sub-compact) also use the K3M. Cub Cadet 7272,
7300, and 7305 tractors (series 7000) are powered by this engine, with
the 7300/7305 models providing 27 hp for lawn and garden applications.
Mini-Excavators (3-Ton Class): Various Japanese mini-excavators in the
2.5 to 3.5 metric ton operating weight class use the K3M. Applications
include Mitsubishi MM30 series, as well as equipment from Komatsu,
Kubota, and Yanmar where Mitsubishi supplied engines under OEM
agreements. The engine's compact footprint enables zero-tail-swing or
reduced-tail-swing excavator designs.
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