Mitsubishi S6E2 Specifications
| Engine Model: Mitsubishi S6E2 |
| Engine Type: 4-cycle inline 6-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 270.6 cu.in (4.43 L) |
| Rated Engine Power: 121 Hp (90 kW) at 2500 rpm |
| Fuel System Type: Direct fuel injection |
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The Mitsubishi S6E2 is a six-cylinder inline
diesel engine representing an evolutionary step in the S6E series,
featuring increased displacement and output while retaining the core
design principles of robustness and smooth operation. This 4.435-liter,
naturally aspirated power plant employs a direct injection combustion
system, offering improved thermal efficiency and fuel economy compared
to earlier indirect injection models within the same family. The
engine’s square bore and stroke configuration contributes to balanced
mechanical forces and a broad, flat torque curve ideal for heavy
industrial applications.
Its six-cylinder layout ensures exceptional primary and secondary
balance, resulting in very low levels of vibration, a critical attribute
for both operator comfort in mobile machinery and stable operation in
generator sets. Constructed with a heavily reinforced cast iron block
and a gear-driven camshaft, the S6E2 prioritizes longevity and
serviceability, establishing itself as a dependable prime mover for
continuous-duty equipment in construction, material handling, and power
generation.
Manufacturer: Mitsubishi Heavy Industries, Ltd.
Engine Model: S6E2.
Engine Type: 4-cycle, water-cooled, vertical inline, direct injection
diesel.
Aspiration: Naturally aspirated.
Emission Compliance: Manufactured in an era preceding stringent modern
regulations; conforms to historical industrial engine standards.
Management System: Mechanical fuel injection with mechanical governor.
Number of Cylinders: 6.
Bore: 98 mm (3.858 in).
Stroke: 98 mm (3.858 in).
Displacement: 4.435 L (4435 cc) (270.6 cu in).
Compression Ratio: 19:1.
Firing Order: 1-5-3-6-2-4.
Rotation Direction: Counter-clockwise when viewed from the flywheel
side.
Maximum Gross Power Output: 90 kW (121 hp) at 2,500 rpm.
Maximum Gross Torque: 343 Nm (253 lb-ft) at 1,600 rpm.
Rated Speed: 2,500 rpm for variable-speed industrial use; 1,500 or 1,800
rpm for constant-speed generator applications. Idle Speed: 650-750 rpm.
The cylinder block is a massive, heavily ribbed casting manufactured
from high-grade gray iron. It utilizes a deep-skirt design that extends
substantially below the crankshaft centerline, creating an extremely
rigid foundation that minimizes block flex, damps vibration, and ensures
precise alignment of all rotating and reciprocating components. The
cylinder bores are machined and honed directly into the block material.
The crankshaft is a forged steel component, supported by seven main
bearings. This seven-main-bearing support system is essential for
maintaining the alignment and minimizing deflection of the long
crankshaft under high torque loads, directly contributing to smooth
operation and extended durability.
Connecting rods are forged steel, fitted with replaceable precision
bearing shells at the crankpin end. The piston pin is a press-fit in the
connecting rod small end. Pistons are aluminum alloy, designed with a
specific re-entrant combustion bowl to generate the controlled air swirl
necessary for efficient direct injection combustion. The piston ring
pack consists of two chrome-plated compression rings and a three-piece
oil control ring.
A single-piece cast iron cylinder head is employed, secured to the block
with a series of high-tensile studs and nuts. The head accommodates one
intake and one exhaust valve per cylinder. Valve seat inserts are
manufactured from hardened, heat-resistant alloy to ensure reliable
sealing and longevity. The valve train operates on an overhead valve
(OHV) design, with the camshaft located in the cylinder block.
The camshaft is gear-driven from the crankshaft, a robust and
maintenance-free timing drive mechanism. The camshaft actuates the
valves via solid pushrods and rocker arms. Rocker arms are mounted on a
stationary shaft fastened to the cylinder head. Valve clearance is set
and maintained by a screw and locknut adjustment on each rocker arm. The
cylinder head is configured for direct injection, with the fuel injector
mounted centrally above each piston.
The engine employs a mechanical, inline pump-line-nozzle fuel injection
system. Core components include a mechanical fuel lift pump, a
six-element inline injection pump, high-pressure steel fuel lines, and
multi-hole pintle injectors. The injection pump is a large jerk-pump
design, driven by the engine's gear train. It supplies fuel at high
pressure directly into the main combustion chamber within the piston
bowl.
A mechanical centrifugal governor, integral to the injection pump,
regulates engine speed by controlling the position of the fuel rack. The
injection timing and fuel delivery curve are mechanically calibrated.
Fuel filtration is a two-stage process, involving a primary
sedimentor/water separator and a secondary fine filter, both critical
for protecting the precision components of the injection system from
contamination and water ingress.
Lubrication is provided by a high-capacity, forced-feed, full-flow wet
sump system. A gear-type oil pump, driven directly from the crankshaft,
draws oil from the sump through a large-diameter pickup tube equipped
with a robust strainer screen. Pressurized oil is routed through a
full-flow, spin-on or canister-type oil filter. After filtration, oil
enters the main oil gallery in the block, supplying the crankshaft main
and connecting rod bearings, the camshaft bearings, and the valve gear
via internal passages and hollow pushrods.
The system is engineered for high volume and pressure to ensure adequate
lubrication and cooling of all internal bearings. The specified engine
oil is API CD or CF grade. Total oil capacity, including the filter, is
12.0 liters (12.7 US qt). The oil pan is a heavy-duty stamped steel or
cast iron component.
Cooling is managed by a pressurized, pump-circulated liquid system. A
centrifugal water pump, driven by a V-belt from the crankshaft pulley,
provides coolant circulation. System operating temperature is regulated
by a wax-pellet type thermostat. Heat rejection occurs via a large
tube-and-fin radiator; the cooling fan is mounted on the engine and is
V-belt driven. The increased displacement generates significant thermal
load, necessitating a high-capacity cooling system.
The cooling system requires a mixture of ethylene-glycol antifreeze and
clean water. A 50/50 mixture is standard for corrosion protection and
freeze resistance. Total cooling system capacity is 16.0 liters (16.9 US
qt) for the engine side, excluding the radiator and external hose
volume.
Intake System: Consists of an air cleaner and a cast iron or aluminum
intake manifold. Exhaust System: Comprises an exhaust manifold and
downpipe connecting to the equipment's exhaust silencer.
Electrical System: Operates on a 12V or 24V system, with 24V being
common for industrial starting applications. A corresponding starter
motor and alternator are fitted. Cold starting is assisted by an intake
manifold heater or, on some variants, glow plugs. An electric stop
solenoid or manual cable acts on the injection pump rack.
Governor: A mechanical centrifugal governor is standard. Generator set
versions employ an isochronous mechanical governor for precise frequency
regulation under varying electrical load.
Length (Front Face of Block to Flywheel Housing): 1,120 mm (44.09 in).
Width (Overall): 610 mm (24.02 in).
Height (Overall, from sump to valve cover): 730 mm (28.74 in).
Dry Weight (with standard accessories): 360 kg (794 lb).
Engine Oil Change: Every 250 operating hours. Oil Filter Replacement:
Every oil change (250 hours). Fuel Filter Replacement: Service sediment
bowl daily; replace secondary filter element every 500 hours. Air
Cleaner Element Service: Clean or replace based on environment and
restriction indicator; inspect regularly. Valve Clearance Adjustment:
Check and adjust every 500 operating hours.
Coolant Replacement: Drain, flush, and refill every 2,000 operating
hours or every two years. Fan Belt Tension Check/Adjustment: Inspect and
adjust tension every 250 hours; replace at signs of wear, glazing, or
cracking. Fuel Injection System Inspection: Have injection pressure and
spray pattern checked by a specialist every 1,500 hours.
Cylinder Head Nuts: Tighten in the specified multi-step crisscross
sequence to a final torque of 137-147 Nm (101-108 lb-ft). Main Bearing
Cap Bolts: 118-127 Nm (87-94 lb-ft).
Connecting Rod Cap Bolts: 88-98 Nm (65-72 lb-ft).
Flywheel to Crankshaft Bolts: 137-147 Nm (101-108 lb-ft).
Fuel Injector Holder: 69-78 Nm (51-58 lb-ft).
Oil Pan Drain Plug: 59-69 Nm (44-51 lb-ft).
Oil Filter Canister/Cartridge: Follow manufacturer's specification;
generally hand-tight plus 3/4 to 1 turn after gasket contact.
The Mitsubishi S6E2 engine was applied in large, heavy-duty industrial
and construction equipment where its combination of smooth power,
substantial torque, and direct injection efficiency was required. Common
applications include: Construction Machinery: Mid-sized hydraulic
excavators (e.g., older Komatsu, Hitachi models in the 20-ton class),
large vibratory rollers, and crawler cranes. Heavy-Duty Forklifts:
Powers large container handlers and high-capacity forklifts (18-30 ton
range) from manufacturers like Mitsubishi, Kalmar, and Fantuzzi.
Generator Sets: A prime mover for industrial and prime power generator
sets in the 60-100 kVA power range. Industrial Pumps: Drives
large-volume, high-pressure pumps for firefighting, oil fields, and
major municipal water projects. Compressors: Used as the diesel driver
for large industrial reciprocating and screw-type air compressors.
Marine Applications: Served as a propulsion engine for small tugboats,
fishing vessels, and passenger ferries, and as a generator drive on
larger commercial vessels. Railroad: Found in some diesel railcar and
locomotive applications for regional service.
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