Mitsubishi S4K Specifications
| Engine Model: Mitsubishi S4K |
| Engine Type: 4-cycle inline 4-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 259.3 cu.in (4.25 L) |
| Rated Engine Power: 83 Hp (62 kW) at 2200 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi S4K is a heavy-duty,
four-cylinder, vertical water-cooled diesel engine within the Mitsubishi
SK Series. This engine family has been used extensively for a long time,
primarily in construction machinery and generator sets, where high
reliability and durability are required. The S4K platform uses a direct
injection combustion system and is available in both naturally aspirated
and turbocharged (S4K-T) configurations.
The engine’s robust design is engineered to deliver high torque at low
revolutions per minute, making it a preferred power source for demanding
applications such as excavators, forklifts, and industrial generators.
The Mitsubishi S4K engine is a four-stroke, compression-ignition diesel
unit featuring an inline four-cylinder layout. The engine has a
long-stroke design, where the stroke measurement exceeds the bore
diameter. This configuration promotes high torque at lower engine
speeds, which is advantageous for construction machinery and power
generation. The combustion system uses direct injection, where fuel is
injected directly into the cylinder, improving thermal efficiency and
reducing specific fuel consumption compared to indirect injection
designs.
Engine Type: Inline 4-cylinder, 4-stroke, water-cooled diesel
Displacement: 4.2 L; 4249 cc (259.3 cu.in)
Bore: 102.0 mm (4.02 in)
Stroke: 130.0 mm (5.12 in)
Firing Order: 1-3-4-2
Compression Ratio: 17.0:1
Combustion System: Direct injection
Aspiration: Naturally aspirated
Maximum Power: 62.0 kW (83.0 hp) at 2200 rpm
Fuel Injection Timing: 20° before top dead center (BTDC)
Rotation (from flywheel end): Counter-clockwise
The cylinder block is constructed from high-strength steel, ensuring
durability under the extreme temperatures and pressures characteristic
of diesel combustion. The engine uses a robust cast iron crankshaft
supported by five main bearings. The block is designed to minimize
weight while maximizing structural rigidity, featuring
precision-machined bores that minimize cylinder wear.
An integrated lubrication network within the block reduces friction and
extends component life compared to designs without such optimized
galleries. The S4K is designed for heavy-duty commercial applications,
capable of prolonged operation in harsh working conditions.
The cylinder head is manufactured from cast iron and utilizes an
overhead valve (OHV) configuration with a single camshaft located in the
cylinder block. The valvetrain operates the valves through pushrods and
rocker arms. This configuration provides two valves per cylinder - one
intake and one exhaust.
Valve Arrangement: 2 valves per cylinder (1 intake, 1 exhaust), OHV
Camshaft Drive: Gear-driven from the crankshaft
Valve Lifters: Mechanical flat tappets
Valve Clearance (Cold): Intake: 0.25 mm (0.010 in); Exhaust: 0.25 mm
(0.010 in)
Valve Adjustment Procedure: With piston at top dead center of
compression stroke for each cylinder, adjust rocker arm screw to
specified clearance.
The fuel system is a direct injection design utilizing an in-line
mechanical injection pump. This mechanical system is highly valued for
its serviceability in remote locations, as it is free from the
electronic controls found on later engines. The in-line pump generates
high pressure for the injectors. A mechanical centrifugal governor
maintains engine speed under varying loads, which is critical for
generator applications requiring frequency stability.
Injection Pump Type: Mechanical in-line
Governor Type: Mechanical centrifugal governor
Injector Type: Mechanical multi-hole nozzle
Injection Order: 1-3-4-2
Fuel Type: Diesel fuel (ASTM No.2-D)
Fuel Filter: Spin-on type with replaceable element
The lubrication system is a full-pressure, wet-sump design. A gear-type
oil pump circulates oil through a full-flow spin-on oil filter. The
system is designed to maintain stable oil pressure during sustained
high-load operation, such as generator duty or heavy excavation work.
Oil Capacity (Naturally Aspirated): 13.0 L; 13.7 qt
Recommended Oil Grade: SAE 15W-40 meeting API classification CF, CF-4,
or CH-4
Oil Pressure: Information missing
Oil Filter Type: Spin-on, full-flow
The cooling system is a pressurized water-cooled design utilizing a
belt-driven centrifugal water pump. A wax-pellet thermostat regulates
coolant temperature by controlling flow between the engine and the
radiator. The robust cooling system is designed to handle the high
thermal loads generated during low-speed, high-torque operations such as
excavating or mining. A mechanically driven engine cooling fan provides
forced airflow through the radiator.
Water Pump Type: Centrifugal, belt-driven
Cooling Fan Type: Mechanical, belt-driven
Electrical System: 24-volt system with a 5.0 kW starter motor.
Charging Alternator: 24V-35A or 24V-50A depending on the application
specification.
Flywheel Housing: SAE 3 standard industrial configuration.
Starting Aid: Glow plug system for cold starting assistance; glow plug
activation time dependent on ambient temperature.
Intake System: Air is drawn through a dry-type dual-element air cleaner.
Exhaust System: A cast iron exhaust manifold collects exhaust gases.
Emissions: Complies with applicable Tier/Stage standards depending on
production year and region; the S4K is widely used in emission-regulated
markets worldwide.
Overall Length: 838.5 mm (33.0 in)
Overall Width: 638.5 mm (25.1 in)
Overall Height: 872.0 mm (34.3 in)
Dry Weight: 340-400 kg (750-882 lb)
Valve Clearance (Cold): 0.25 mm (0.010 in) for both intake and exhaust
Valve Adjustment Interval: Inspect and adjust every 1000 operating
hours.
Engine Oil and Filter Replacement Interval: 250-500 hours depending on
the severity of the application.
Fuel Filter Replacement Interval: 500 operating hours.
Air Filter Elements: Check daily in dusty environments; replace element
based on restriction indicator.
Coolant Replacement Interval: 2000 operating hours or 2 years.
Injection Timing: 20° BTDC
Fuel Injection Pump Service: Perform by authorized diesel service
center.
Cylinder Head Bolts: 108-118 Nm (80-87 lb-ft)
Main Bearing Cap Bolts: 100-110 Nm (74-81 lb-ft)
Connecting Rod Cap Nuts: 50-60 Nm (37-44 lb-ft)
Flywheel Bolts: 85-95 Nm (63-70 lb-ft)
Crankshaft Pulley Bolt: 180-200 Nm (133-148 lb-ft)
Injection Pump Drive Gear Nut: 50-60 Nm (37-44 lb-ft)
Injector Hold-Down Bolts: 60-70 Nm (44-52 lb-ft)
Rocker Arm Shaft Bracket Bolts: 40-50 Nm (30-37 lb-ft)
Oil Pan Bolts: 20-25 Nm (15-18 lb-ft)
Water Pump Bolts: 20-25 Nm (15-18 lb-ft)
The Mitsubishi S4K engine is utilized across a broad range of heavy
industrial applications, often serving as the power source for yellow
machinery from brands like Caterpillar and Kato.
Excavators: Commonly installed in compact and medium excavators,
including models such as the Caterpillar 312 and CAT E200B. It provides
the high low-end torque required for hydraulic systems during digging
and lifting operations.
Forklifts: Used in heavy-duty Mitsubishi and TCM material handling
units, providing stable power delivery for warehouse and logistics
applications.
Construction Machinery: Powers mini excavators, skid steer loaders, and
compact backhoes. Its compact size allows integration into
space-constrained machinery while resisting dust, vibration, and
temperature extremes.
Generator Sets (Gensets): Configured for industrial diesel generator
sets in the 30-50 kVA range for prime or standby power, delivering
stable voltage and frequency control.
Agricultural Machinery: Used in tractors, combine harvesters, and
irrigation pumps where durability under sustained load is required.
Mining Machinery: Powers compact excavators and support equipment in
underground and surface mining operations, with features such as a
robust cooling system to maintain optimal engine temperature.
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