Mitsubishi S2E Specifications
| Engine Model: Mitsubishi S2E |
| Engine Type: 4-cycle 2-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 79.6 cu.in (1.31 L) |
| Rated Engine Power: 24.7 Hp (18.4 kW) at 2400 rpm |
| Fuel System Type: Indirect fuel injection |
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The Mitsubishi S2E is a compact, two-cylinder
diesel engine engineered for light industrial and agricultural
applications where simplicity, durability, and fuel economy are
essential. This 1.305-liter, naturally aspirated power plant employs an
indirect injection combustion system with a swirl pre-combustion
chamber, delivering smooth and quiet operation with excellent
cold-starting characteristics. Its square bore and stroke design
provides a balanced mechanical layout, contributing to a stable torque
output suitable for constant-speed duties and moderate variable loads.
As a two-cylinder engine, it presents a cost-effective and
space-efficient solution, designed for integration into compact
machinery. The engine's construction prioritizes robustness and
serviceability, featuring a sturdy cast iron block and a
straightforward, gear-driven valve train. The S2E is recognized for its
dependable performance in applications where extreme power is not
required, but long-term reliability and low operating costs are
paramount.
Manufacturer: Mitsubishi Heavy Industries, Ltd.
Engine Model: S2E.
Engine Type: 4-cycle, water-cooled, vertical inline, indirect injection
diesel.
Aspiration: Naturally aspirated.
Emission Compliance: Manufactured prior to modern emission regulations;
conforms to historical industrial standards.
Management System: Mechanical fuel injection with mechanical governor.
Number of Cylinders: 2.
Bore: 94 mm (3.701 in).
Stroke: 94 mm (3.701 in).
Displacement: 1.305 L (1305 cc) (79.6 cu in).
Compression Ratio: 19:1.
Firing Order: 1-2.
Rotation Direction: Counter-clockwise when viewed from the flywheel
side.
Maximum Gross Power Output: 18.4 kW (24.7 hp) at 2,400 rpm
(representative value; output varies by specific variant and
application).
Maximum Gross Torque: 62 Nm (45.7 lb-ft) at 1,600 rpm.
Rated Speed: 2,200-2,400 rpm for industrial applications; 1,500 or 1,800
rpm for constant-speed generator duty. Idle Speed: 700-800 rpm.
The cylinder block is a robust, compact casting manufactured from
high-strength gray iron. Its design provides a solid foundation for the
two cylinders, with adequate webbing between the bores and around the
main bearing saddles to manage internal forces. The cylinder bores are
machined and honed directly into the block material. The crankshaft is a
forged steel or high-grade cast iron component, supported by three main
bearings. This three-main-bearing configuration is standard for a
two-cylinder inline engine, providing necessary support to manage the
inherent primary imbalance characteristic of this layout.
Counterweights on the crankshaft are designed to mitigate this
imbalance. 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 crown profile compatible with the indirect
injection swirl chamber. The piston ring pack consists of two
compression rings and one oil control ring.
A single-piece cast iron cylinder head is employed, secured to the block
with studs and nuts. The head accommodates one intake and one exhaust
valve per cylinder. Valve seat inserts are manufactured from hardened
material for wear resistance. 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, providing a positive and
reliable timing drive.
The camshaft actuates the valves via solid pushrods and rocker arms.
Rocker arms are mounted on a stationary shaft attached to the cylinder
head. Valve clearance is set and maintained by a screw and locknut
adjustment on each rocker arm, a standard maintenance procedure. The
cylinder head incorporates the indirect injection pre-combustion (swirl)
chamber for each cylinder, which houses a glow plug for cold starting
assistance.
The engine utilizes a mechanical, inline pump-line-nozzle fuel injection
system. Core components are a mechanical fuel lift pump, a two-element
inline injection pump, high-pressure steel fuel lines, and pintle-type
injectors. The injection pump is a jerk-pump design, driven by the
engine's gear train. It supplies fuel at high pressure to nozzles that
discharge into the pre-combustion swirl chamber.
A mechanical centrifugal governor, integral to the injection pump,
regulates engine speed by controlling the fuel rack position. The system
is calibrated for specific power and speed requirements. Fuel filtration
is provided by a primary sediment bowl and a secondary inline paper
filter element, essential for protecting the precision components of the
injection system.
Lubrication is provided by a forced-feed, full-flow wet sump system. A
gear-type oil pump, driven from the crankshaft, draws oil from the sump
through a pickup tube and screen. Pressurized oil is directed through a
full-flow, replaceable cartridge or canister-type oil filter. Filtered
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 designed for reliable lubrication with a simple network of
internal oil passages. The specified engine oil is API CC or CD grade.
Total oil capacity is 4.5 liters (4.8 US qt), including the filter. The
oil pan is a stamped steel 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 temperature is regulated by a
wax-pellet type thermostat.
Heat rejection occurs via a tube-and-fin radiator; the cooling fan is
mounted on the engine and is V-belt driven. The cooling system requires
a mixture of water and ethylene-glycol antifreeze. Total cooling system
capacity is 3.5 liters (3.7 US qt) for the engine side, excluding the
radiator and external hose volume.
Intake System: Consists of an oil bath or dry-type air cleaner and a
cast iron intake manifold. Exhaust System: Comprises a cast iron exhaust
manifold and a downpipe.
Electrical System: Operates on a 12V system. A 12V starter motor and a
DC generator or alternator are fitted. The engine incorporates a glow
plug system for cold starting, controlled by a key-switch or manual
timer. An electric stop solenoid or manual pull cable acts on the
injection pump rack.
Governor: A mechanical centrifugal governor is integrated within the
fuel injection pump. Constant-speed applications may use a dedicated
isochronous governor.
Length (Front Face of Block to Flywheel Housing): 573 mm (22.56 in).
Width (Overall): 550 mm (21.65 in).
Height (Overall, from sump to valve cover): 734 mm (28.90 in).
Dry Weight (with standard accessories): 180 kg (397 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 oil bath or replace dry element every
100-250 hours, depending on environment.
Valve Clearance Adjustment: Check and adjust every 500 operating hours.
Coolant Replacement: Drain, flush, and refill every 1,000 operating
hours or annually. Fan Belt Tension Check/Adjustment: Inspect and adjust
tension every 250 hours; replace at signs of wear. Fuel Injection System
Inspection: Check injection pressure and spray pattern every 1,500
hours.
Cylinder Head Bolts: Tighten in the specified sequence to a final torque
of 108-118 Nm (80-87 lb-ft).
Main Bearing Cap Bolts: 88-98 Nm (65-72 lb-ft).
Connecting Rod Cap Bolts: 69-78 Nm (51-58 lb-ft).
Flywheel to Crankshaft Bolts: 108-118 Nm (80-87 lb-ft).
Fuel Injector Holder: 59-69 Nm (44-51 lb-ft).
Glow Plugs: 15-20 Nm (11-15 lb-ft).
Oil Pan Drain Plug: 39-49 Nm (29-36 lb-ft).
Oil Filter Canister: Tighten the center bolt to 20-25 Nm (15-18 lb-ft).
The Mitsubishi S2E engine was widely used in compact industrial and
agricultural machinery where a small, reliable two-cylinder diesel was
optimal. Common applications include: Agricultural Tractors: Small
agricultural and garden tractors, particularly in Japanese and Asian
markets (e.g., Iseki, Satoh). Construction Equipment: Very small
vibratory rollers, concrete mixers, and light compaction equipment.
Generator Sets: Mobile and stationary generator sets in the 10-15 kVA
power range. Pumping Equipment: Irrigation pumps, small firefighting
pumps, and industrial transfer pumps. Material Handling: Light-duty
forklifts and hydraulic power packs. Marine Applications: Auxiliary
power for small boats and as a propulsion engine for tiny workboats.
Agricultural Machinery: Powers rice transplanters, threshers, and other
small implements.
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