Mitsubishi S6K-T Specifications
| Engine Model: Mitsubishi S6K-T |
| Engine Type: 4-cycle inline 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 389 cu.in (6.37 L) |
| Rated Engine Power: 140-180 Hp (103-134 kW) at 2200 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi S6KT, also known as the S6K-T,
is a 6.4-liter inline 6-cylinder, 4-stroke, water-cooled turbocharged
diesel engine from the Mitsubishi S-series diesel family. This engine
gained prominence as a power unit for heavy construction equipment,
serving as the core diesel engine for the Caterpillar 320 series
excavators and a range of industrial machinery. The "T" designation
indicates turbocharging, a feature that supplies increased air density
to the combustion chambers, enabling higher torque output at reduced
engine speeds. The S6KT was engineered for continuous-duty cycles in
demanding environments.
The Mitsubishi S6K-T is a turbocharged, inline 6-cylinder, 4-stroke
diesel engine utilizing a water-cooled cooling system and direct fuel
injection. The displacement is 6.4 L. The engine features a cast iron
cylinder block and a cast iron or aluminum alloy cylinder head. The
valvetrain is an overhead valve pushrod design.
The fuel system employs an electronically controlled inline injection
pump. The lubrication system is a full-pressure design with a gear-type
oil pump. Cooling is managed by a belt-driven centrifugal water pump.
The engine is designed for heavy-duty applications, including
construction machinery, agricultural equipment, and power generation
systems.
Engine Type: Inline 6-cylinder, 4-stroke, water-cooled, turbocharged
diesel
Displacement: 6.4 L (6373 cc / 389 cu.in)
Bore: 102.0 mm (4.02 in)
Stroke: 130.0 mm (5.12 in)
Compression Ratio: 17.0:1
Maximum Power (Rated): 103-134 kW (140-180 hp) at 2100-2200 rpm
Maximum Torque: 441 Nm (325 lb-ft) at 1400 rpm
Firing Order: 1-5-3-6-2-4
Aspiration: Turbocharged with optional intercooler on certain variants
Emission Standard: Euro 4 to Euro 6 compliance depending on variant
Valve Clearance (Cold): Intake 0.25 mm (0.010 in); Exhaust 0.25 mm
(0.010 in)
Fuel Injection Timing: 10° BTDC
Electrical System: 24V
The cylinder block is constructed from high-strength cast iron,
providing the structural rigidity required to withstand combustion
pressures and mechanical loads in heavy equipment. The block is a
monobloc design with recessed cylinder bores machined directly into the
parent material, eliminating replaceable liners.
The block incorporates a deep-skirt design extending below the
crankshaft centerline, which supports the seven main bearing webs for
enhanced crankshaft stability under continuous low-speed, high-torque
operation. The water jacket surrounds the upper portion of each
cylinder, integrated with the cooling system. The block weighs 490 kg
(1080 lb). Connecting Rods: Forged steel I-beam design, with replaceable
bearing shells.
Crankshaft: The crankshaft is forged or cast from high-strength steel,
supported by seven main bearings. Each main bearing and connecting rod
journal is induction-hardened for wear resistance. The crankshaft is
equipped with a torsional vibration damper at the front end. The
crankshaft dimensions are approximately 750 mm (29.5 in) in length,
weighing 118 kg (260 lb).
Pistons: Cast aluminum alloy with a high-silicon content. Three piston
rings: two compression rings and one oil control ring. Oil jets (piston
cooling nozzles) are integrated into the cylinder block crankcase to
spray the underside of the piston crowns.
The cylinder head is manufactured as a one-piece casting. Certain
applications use cast iron for maximum durability, while others employ
aluminum alloy for reduced mass. The overhead valve arrangement uses a
pushrod actuation system with a camshaft positioned within the cylinder
block.
The design employs 2 valves per cylinder (one intake valve, one exhaust
valve), for a total of 12 valves. The valve seats and guides are pressed
into the head. Rocker arms are mounted on a shaft and actuated by
pushrods driven from the camshaft.
The fuel system is a direct injection architecture. An electronically
controlled inline injection pump, positioned on the side of the engine
and driven by the timing gears, supplies high-pressure fuel to the
injectors. A mechanical governor maintains consistent engine speed under
varying loads. A fuel feed pump draws diesel from the tank through a
primary filter and delivers it to the injection pump.
High-pressure injection lines route fuel to the nozzle-type injectors.
Excess fuel returns to tank via a leak-off line. The engine is adaptable
to electronic control modules (ECM) for optimizing fuel delivery based
on real-time sensor inputs. The standard application provides 300 L
(79.3 gal) tank capacity, offering a range of 4800 km to 5500 km (2980
mi to 3420 mi) on a full tank.
The lubrication system is a fully pressurized, wet-sump design. A
gear-type oil pump is mounted on the timing gear cover and driven by the
crankshaft. The pump draws oil through a suction strainer from a steel
oil pan.
A spin-on full-flow oil filter is mounted externally to the cylinder
block. A pressure relief valve regulates system pressure. The total oil
capacity inclusive of the filter is 30.0 L (31.7 qt). The recommended
oil classification is API CF or higher.
The cooling system is a pressurized, thermostatically controlled liquid
circuit utilizing a water-cooled design. A belt-driven centrifugal water
pump circulates a glycol-based coolant through water jackets within the
cylinder block and cylinder head. A wax-pellet thermostat regulates
coolant flow to the radiator to maintain the engine within the optimal
operating temperature range.
For high-output or continuous-duty applications, an optional radiator
with enhanced cooling capacity is available. A separate charge-air
cooler (intercooler) reduces intake air temperature after the
turbocharger compressor.
Timing Drive: Gear train drive. The crankshaft gear drives an
intermediate idler gear, which rotates the camshaft gear and the
injection pump gear. No timing belt or chain is used.
Turbocharger: The engine is equipped with a Mitsubishi TD06H
turbocharger. The turbocharger is both water-cooled and oil-cooled. It
utilizes a journal bearing system.
Starting System: A 24 V electric starter motor is mounted to the
flywheel housing.
Flywheel: A heavy flywheel is bolted to the crankshaft flange, providing
rotational inertia for smooth operation at low engine speeds.
Length: 1182 mm (46.5 in) measured from fan hub to flywheel housing
Width: 987 mm (38.9 in) at engine mount centers
Height: 831 mm (32.7 in) from oil pan rail to rocker cover
Dry Weight (without flywheel or fluids): 475 kg (1047 lb)
Engine Oil Capacity (with filter): 30.0 L (31.7 qt)
Recommended Oil Specification: API CF, CF-4, CG-4, or higher; viscosity
SAE 15W-40
Coolant Capacity (engine only): 15 L to 20 L (15.9 qt to 21.1 qt)
Valve Clearance Adjustment Interval: 500 operating hours
Oil Change Interval (normal service): 250 operating hours
Oil Filter Replacement Interval: 250 operating hours (at every oil
change)
Fuel Filter Replacement Interval: 250 operating hours
Fuel Injection Timing: 10° BTDC (static)
Cylinder Head Bolts, Stage 1: 60 Nm (44 lb-ft)
Cylinder Head Bolts, Stage 2: 90 Nm (66 lb-ft)
Cylinder Head Bolts, Stage 3: 123 Nm (91 lb-ft)
Main Bearing Cap Bolts: 113 Nm (83 lb-ft)
Connecting Rod Cap Nuts: 52 Nm (38 lb-ft)
Crankshaft Pulley Bolt (center): 245 Nm (181 lb-ft)
Flywheel-to-Crankshaft Bolts: 118 Nm (87 lb-ft)
Rocker Arm Shaft Support Bolts: 35 Nm (26 lb-ft)
Rocker Arm Adjuster Locknut: 25 Nm (18 lb-ft)
Injection Pump Mounting Nuts: 40 Nm (30 lb-ft)
Injector Clamp Bolts: 25 Nm (18 lb-ft)
Intake Manifold Bolts: 35 Nm (26 lb-ft)
Exhaust Manifold Nuts: 45 Nm (33 lb-ft)
Turbocharger Mounting Nuts: 35 Nm (26 lb-ft)
Oil Pan Bolts: 20 Nm (15 lb-ft)
Oil Filter (spin-on): 15 Nm (11 lb-ft)
The Mitsubishi S6KT engine was installed in a range of heavy
construction and industrial machinery from the mid-1990s to the present.
Excavators:
Caterpillar 320
Caterpillar 320B
Caterpillar 320C
Caterpillar 320L
Caterpillar E200B
Industrial Equipment:
Heavy forklifts (various manufacturers)
Wheel loaders
Bulldozers
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