Mitsubishi K4E Specifications
| Engine Model: Mitsubishi K4E |
| Engine Type: 4-cycle inline 4-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 86.4 cu.in (1.42 L) |
| Rated Engine Power: 31 Hp (23.1 kW) at 2500 rpm |
| Fuel System Type: Indirect injection |
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The Mitsubishi K4E is a vertical, water-cooled,
4-stroke, 4-cylinder in-line diesel engine with a displacement of 1.415
liters (1415 cc). This engine is a member of the Mitsubishi K-series
diesel family, which includes the K3D, K3E, K4D, K4F, K4N, and K4M
variants. The K4E is highly regarded for its compact size, durability,
and power density, making it a common powerplant in a wide variety of
industrial and construction equipment. Its applications include
mini-excavators, wheel loaders, compact tractors, backhoe loaders,
generators, and other stationary machinery.
The Mitsubishi K4E utilizes a naturally aspirated indirect injection
(IDI) combustion system. This design choice contributes to smoother and
quieter operation compared to direct injection engines of similar
displacement. The engine features a cast iron cylinder block and
cylinder head, a configuration known for longevity under continuous load
conditions. A mechanical governor ensures stable operation under varying
loads.
The K4E is recognized in the equipment industry for its reliability and
the widespread availability of replacement parts, supported by numerous
variants such as the K4E-31HS, K4E-31FL, K4E-31DS, K4E-31DSA, and
K4E-61HMG.
The Mitsubishi K4E is a 4-stroke, compression-ignition, in-line
4-cylinder diesel engine. The engine is naturally aspirated without any
turbocharging or supercharging systems. Total displacement measures
1,415 cc (86.4 cu.in). The bore and stroke dimensions are 76.0 mm x 78.0
mm (2.99 in x 3.07 in).
This near-square design (oversquare by a small margin) provides a
balanced performance between low-speed torque and engine responsiveness.
The compression ratio is 18.0:1. The firing order is 1-3-4-2, a standard
layout for in-line 4-cylinder engines.
Maximum Power (Industrial, Intermittent): 23.1 kW (31 hp) @ 2,200-2,500
rpm
Maximum Power (Tractor Rating, Continuous): 17.2 kW (23 hp)
Maximum Torque: 85 Nm (63 lb-ft) @ 1,800 rpm (based on K4E-1 series)
Rated Engine Speed (Industrial): 2,500 rpm
Low Idle Speed: 750-850 rpm (adjusted via mechanical governor)
High Idle Speed (no load, governed): 2,750-2,800 rpm
Combustion System: Indirect injection (IDI) with pre-combustion chamber
Governor Type: Mechanical, centrifugal flyweight (variable speed)
The cylinder block is a one-piece, cast iron design. This material
provides excellent heat dissipation and resistance to mechanical stress
under continuous load conditions. The block features 5 main bearing
supports. The cylinders are integral to the block (parent bore design)
on most variants; however, some industrial variants use replaceable dry
liners. The block architecture includes a deep skirt for increased
rigidity.
The crankshaft is cast from nodular iron, with induction-hardened
journal surfaces. The crankshaft is supported by five main bearings,
with thrust washers located at the center bearing (number 3) to control
axial play. Connecting rods are forged steel, machined as matched sets
with the cap. The pistons are cast aluminum alloy with a high-ring
groove insert for the top compression ring. Each piston is fitted with
three rings: two compression rings (upper and intermediate) and one oil
control ring.
Number of Main Bearings: 5
Main Bearing Journal Diameter: 56.0 mm (2.20 in)
Connecting Rod Length (center-to-center): 118.0 mm (4.65 in)
Connecting Rod Big End Bore: 46.0 mm (1.81 in)
Piston Pin Diameter: 22.0 mm (0.87 in)
Piston Cooling: Splash and mist lubrication (no dedicated oil jets)
The cylinder head is a single, cast iron casting spanning all 4
cylinders. The head incorporates pre-combustion chambers (swirl
chambers) for each cylinder. These chambers are located within the
cylinder head, into which fuel is injected. A glow plug is mounted in
each pre-combustion chamber to aid cold starting. The cylinder head
surface must be flat within 0.05 mm (0.002 in) for proper gasket
sealing.
The valvetrain uses a camshaft located in the cylinder block. The
camshaft actuates valves via mechanical lifters (tappets), pushrods, and
rocker arms. This cam-in-block arrangement is durable and allows easy
valve lash adjustment. Each cylinder has two valves: one intake and one
exhaust (8 valves total). Valve lash adjustment is mechanical, performed
via a setscrew and locknut on each rocker arm.
Valve Arrangement: Overhead valve, cam-in-block, pushrod actuated, 2 per
cylinder
Intake Valve Diameter: 34.0 mm (1.34 in)
Exhaust Valve Diameter: 30.0 mm (1.18 in)
Valve Lift (intake and exhaust): 7.8 mm (0.307 in)
Valve Lash (cold, intake): 0.25 mm (0.010 in)
Valve Lash (cold, exhaust): 0.25 mm (0.010 in)
Valve Lash Adjustment Interval: 600 hours
Camshaft Drive: Gear train from the crankshaft (helical-cut gears)
The fuel system uses mechanical indirect injection. A gear-type transfer
pump, integrated into the injection pump housing, draws fuel from the
tank and supplies it to the injection pump at low pressure. The
injection pump is an in-line, mechanical unit (Bosch M-type or
equivalent) with a separate pumping plunger for each cylinder. The pump
incorporates a mechanical centrifugal governor that maintains set engine
speed regardless of load. A cold start device on the injection pump
advances injection timing for improved starting.
The injection pump delivers fuel at high pressure through individual
high-pressure lines to each injector. The injectors are mechanical
nozzle-and-holder types, installed into the cylinder head and injecting
into the pre-combustion chamber. The injector nozzle is a throttle-type
(pintle) design with a single orifice, producing a cone-shaped spray
pattern. A manual primer pump is located on the fuel filter housing for
bleeding air after filter changes.
Injection Pressure (nominal): 118-127 bar (1,710-1,840 psi)
Injector Type: Mechanical, throttle-type nozzle (pintle)
Injection Timing (static, industrial): 21° BTDC
Injection Timing (static, tractor): 18-20° BTDC
Governor Type: Mechanical, variable speed with torque control
Fuel Filtration: Single spin-on filter with water separator and sediment
bowl
The lubrication system is a full-pressure, forced-feed design using a
gear-type oil pump. The oil pump is mounted inside the oil pan and
driven by a shaft from the camshaft gear. Oil is drawn from the sump
through a wire mesh strainer, pressurized by the pump, and then routed
through a full-flow oil filter (spin-on, cellulose media). A bypass
valve opens at 1.5 bar (22 psi) differential pressure if the filter
becomes restricted.
After filtration, oil is distributed to the main bearings, connecting
rod bearings, camshaft bearings, and rocker arm shaft. The rocker arm
shaft receives oil through hollow pushrods on some variants or through
an external oil line on others. The oil pan is a stamped steel sump with
a large capacity. A crankcase ventilation system (open type, road draft
tube) vents blow-by gases to the atmosphere on early variants; later
variants incorporate a closed PCV (Positive Crankcase Ventilation)
system with a breather hose routed to the intake manifold.
Oil Capacity (with filter, standard sump): 5.5 L (5.8 U.S. qt)
Oil Pressure (rated speed, 2,500 rpm): 300-400 kPa (43-58 psi)
Oil Pressure (low idle, 800 rpm, hot): 70 kPa (10 psi) minimum
Recommended Oil Viscosity: SAE 10W-30 or 15W-40 (API CD, CE, or CF
rating)
Oil Change Interval (industrial duty): 250-300 hours or annually
Oil Pan Type: Stamped steel
The cooling system is a pressurized, liquid-cooled design with a
centrifugal water pump. The water pump is belt-driven from the
crankshaft pulley and uses a sealed ball bearing and a carbon-ceramic
face seal. Coolant flows from the lower radiator tank into the pump,
then through the cylinder block water jackets, upward through the
cylinder head, and out through the thermostat housing. A bypass passage
permits coolant circulation through the block and head until the
thermostat opens.
The system incorporates a wax-pellet thermostat located in a housing at
the front of the cylinder head. The thermostat begins opening at 82°C
(180°F) and is fully open at 95°C (203°F). The radiator is a
vertical-flow, tube-and-fin design with a pressure cap. An engine-driven
fan (direct or viscous clutch) moves air across the radiator.
Coolant Capacity (engine only, no radiator): 2.5 L (2.6 U.S. qt)
Coolant Capacity (engine with standard radiator): 6.0-7.0 L (6.3-7.4
U.S. qt)
Thermostat Opening Temperature: 82°C (180°F)
Thermostat Fully Open Temperature: 95°C (203°F)
Radiator Cap Pressure: 90-110 kPa (13-16 psi)
Water Pump Type: Centrifugal, belt-driven
Coolant Type: Heavy-duty low-silicate ethylene glycol antifreeze mixed
50/50 with distilled water.
Electrical System: The electrical system is 12-volt with negative
ground. The starter motor is a pre-engaged type with an integral
solenoid, rated at 1.6 kW (2.1 hp). The alternator is a 12-volt,
internally regulated unit with an output of 35-40 A. The battery is a
lead-acid, heavy-duty type with a capacity of 60-80 Ah. The engine is
equipped with four glow plugs (one per cylinder) for cold starting
assistance. The glow plugs are controlled by a glow plug heating module
(relay and timer), which activates the plugs for 5-15 seconds depending
on coolant temperature. A glow plug indicator lamp on the dashboard
signals when the heating cycle is active.
Intake and Exhaust Systems: The intake manifold is a cast iron,
single-plane design. The air cleaner is a dry-type, two-stage element
with a restriction indicator. The exhaust manifold is a cast iron,
single-outlet design. No exhaust gas recirculation (EGR) or
after-treatment system is present on this pre-Tier 1 engine.
Engine Control: No electronic control unit is present. Engine governing
is purely mechanical. The throttle lever connects to the injection pump
governor via a cable or linkage. An excess fuel button on the injection
pump provides additional fuel for cold starting.
Overall Length (front of fan hub to flywheel housing face): 650 mm (25.6
in)
Overall Width (valve cover edge to oil pan edge): 490 mm (19.3 in)
Overall Height (bottom of oil pan to top of rocker cover): 720 mm (28.3
in)
Dry Weight (complete engine, no fluids): 135 kg (298 lb)
Valve Lash (cold, intake): 0.25 mm (0.010 in)
Valve Lash (cold, exhaust): 0.25 mm (0.010 in)
Valve Lash Adjustment Interval: 600 hours or 12 months
Compression Pressure (standard, new): 3,000 kPa (435 psi) minimum
Compression Pressure (service limit): 2,400 kPa (348 psi)
Maximum Compression Variation Between Cylinders: 300 kPa (44 psi)
Engine Oil Change Interval: 250-300 hours or annually
Oil Filter Change Interval: Every oil change (250-300 hours)
Fuel Filter Change Interval: 500 hours or annually
Coolant Change Interval: 1,000 hours or 2 years
Air Cleaner Element (primary): Service when restriction indicator shows
6.2 kPa
Glow Plug Check Interval: 500 hours (measure resistance; replace if open
circuit)
Injector Inspection Interval: 600 hours (check opening pressure and
spray pattern)
Injection Timing Check Interval: 1,000 hours
Cylinder Head Bolts (Large, M12 x 1.75), Step 1: 30 Nm (22 lb-ft).
Cylinder Head Bolts (Large, M12 x 1.75), Step 2: 70 Nm (52 lb-ft).
Cylinder Head Bolts (Large, M12 x 1.75), Step 3: 118-127 Nm (87-94
lb-ft).
Cylinder Head Bolts (Small, M10 x 1.25), Step 1: 20 Nm (15 lb-ft).
Cylinder Head Bolts (Small, M10 x 1.25), Step 2: 50 Nm (37 lb-ft).
Cylinder Head Bolts (Small, M10 x 1.25), Step 3: 78-88 Nm (58-65 lb-ft).
Main Bearing Cap Bolts (M10 x 1.25), Step 1: 30 Nm (22 lb-ft).
Main Bearing Cap Bolts (M10 x 1.25), Step 2: 103 Nm (76 lb-ft).
Connecting Rod Cap Nuts (M9 x 1.0): 49-54 Nm (36-40 lb-ft)
Flywheel Bolts (M10 x 1.25): 83 Nm (61.5 lb-ft).
Flywheel Housing-to-Block Bolts (M8 x 1.25): 25 Nm (18 lb-ft).
Camshaft Bearing Cap Bolts (M8 x 1.25): 25 Nm (18 lb-ft).
Rocker Arm Shaft Bracket Bolts (M8 x 1.25): 25 Nm (18 lb-ft).
Rocker Cover Bolts (M6 x 1.0): 8 Nm (6 lb-ft).
Injector Hold-Down Clamp Bolts (M8 x 1.25): 22 Nm (16 lb-ft).
Intake Manifold Bolts (M8 x 1.25): 22 Nm (16 lb-ft).
Exhaust Manifold Bolts (M10 x 1.25): 35 Nm (26 lb-ft).
Glow Plugs (M8 x 1.0): 15 Nm (11 lb-ft).
Oil Pan Bolts (M8 x 1.25): 22 Nm (16 lb-ft).
Water Pump Bolts (M8 x 1.25): 22 Nm (16 lb-ft).
Thermostat Housing Bolts (M8 x 1.25): 22 Nm (16 lb-ft).
Starter Motor Bolts (M10 x 1.25): 40 Nm (30 lb-ft).
Alternator Bracket Bolts (M10 x 1.25): 40 Nm (30 lb-ft).
Crankshaft Pulley Bolt (M14 x 1.5): 120 Nm (89 lb-ft).
The Mitsubishi K4E engine was utilized in construction, agricultural,
and industrial equipment worldwide.
Construction Equipment (Mini-Excavators and
Wheel Loaders):
Airman HM30S and HM35S backhoe loaders and mini-excavators.
Hanix N260, N260-2, N300-2, N350, N350-2, M212T, and M315T excavators.
Hitachi UE30 and UE40 mini-excavators.
Hokuetsu HM30S, HM30S-2, HM35S, and HM35S-2 mini-excavators.
Mitsubishi MX35, MX45, ME25, and ME35 mini-excavators.
Pel-Job LS2000 excavator.
Terex HR5, HR8, HR8A, and HR10 excavators.
Mitsubishi wheel loaders.
Furukawa FL30 excavator.
Agricultural Equipment (Tractors):
Mitsubishi MT21, MT22, MT23, MT24, MT25, MT26, MT27, MT30, MT33, MT185,
MT205.
Mitsubishi MTX225, and MTX245 compact tractors.
Mitsubishi MT14, MT15, MT16, MT17, MT18, and MT20 tractors.
Iseki tractors (various models within the TX, TU, and TS series).
Industrial Equipment:
HFL H4G20M3 generator set.
Stationary industrial power units.
Small marine auxiliary drives.
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