Mitsubishi S3E Specifications
| Engine Model: Mitsubishi S3E |
| Engine Type: 4-cycle inline 3-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 119.4 cu.in (1.96 L) |
| Rated Engine Power: 37 Hp (27.6 kW) at 2400 rpm |
| Fuel System Type: Indirect fuel injection |
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The Mitsubishi S3E is a three-cylinder inline
diesel engine engineered for reliable and durable performance in
mid-range industrial and agricultural applications. This 1.956-liter,
naturally aspirated power unit utilizes an indirect injection combustion
system with a swirl pre-combustion chamber, a design that delivers
smooth operation, controlled combustion noise, and robust cold-starting
capability. The three-cylinder configuration provides a favorable
compromise between compact size, cost, and operational smoothness,
exhibiting less inherent vibration than a two-cylinder engine while
remaining more space-efficient than a four-cylinder.
Its square bore and stroke design contributes to balanced mechanical
forces and a consistent torque curve. Constructed with a heavy-duty cast
iron block and a gear-driven camshaft, the S3E emphasizes longevity and
straightforward maintenance. It serves as a dependable power source for
equipment requiring steady power delivery under continuous load, such as
generator sets, agricultural machinery, and medium-duty material
handling equipment.
Manufacturer: Mitsubishi Heavy Industries, Ltd.
Engine Model: S3E.
Engine Type: 4-cycle, water-cooled, vertical inline, indirect injection
diesel.
Aspiration: Naturally aspirated.
Emission Compliance: Manufactured before contemporary emission
regulations; conforms to historical industrial engine standards.
Management System: Mechanical fuel injection with mechanical governor.
Common injection pump is Bosch PES4-A.
Number of Cylinders: 3.
Bore: 94 mm (3.701 in).
Stroke: 94 mm (3.701 in).
Displacement: 1.956 L (1956 cc) (119.4 cu in).
Compression Ratio: 19:1.
Firing Order: 1-3-2.
Rotation Direction: Counter-clockwise when viewed from the flywheel
side.
Maximum Gross Power Output: 27.6 kW (37 hp) at 2,400 rpm (representative
value; varies by governed speed and application).
Maximum Gross Torque: 98 Nm (72.3 lb-ft) at 1,600 rpm.
Rated Speed: 2,200-2,400 rpm for industrial use; 1,500 or 1,800 rpm for
constant-speed generator duty. Idle Speed: 700-800 rpm.
The cylinder block is a robust, heavily webbed casting manufactured from
high-strength gray iron. Its design provides a rigid foundation for the
three cylinders, with substantial material around the cylinder bores and
main bearing saddles to withstand internal combustion pressures.
The cylinder bores are machined and honed directly into the block
material. The crankshaft is a forged steel component, supported by four
main bearings. This four-main-bearing configuration is essential for a
three-cylinder engine, providing critical support to manage the dynamic
forces and ensure stable crankshaft rotation, minimizing vibration.
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 system. 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,
heat-resistant alloy to ensure durability and reliable sealing. 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 positive and maintenance-free timing.
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, a scheduled 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 employs a mechanical, inline pump-line-nozzle fuel injection
system. The system is centered on a Bosch PES4-A or equivalent
multi-element inline injection pump. Core components include a
mechanical fuel lift pump, this injection pump, high-pressure steel fuel
lines, and throttle-type (pintle) 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 position of the fuel rack.
This governor can be configured for all-speed (variable) or
constant-speed operation based on application requirements. Fuel
filtration involves a primary sedimentor/water separator and a secondary
fine filter.
Lubrication is provided by a forced-feed, full-flow wet sump system. A
trochoid (gear) type oil pump, driven directly from the crankshaft,
draws oil from the sump through a pickup tube equipped with a strainer
screen.
Pressurized oil is routed through a full-flow, replaceable cartridge 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 designed for reliable
pressure-feed lubrication. The specified engine oil is API CC, CD, or CF
grade. Total oil capacity is 6.0 liters (6.3 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 forced coolant circulation. System operating 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 ethylene-glycol antifreeze and
clean water. A 50/50 mixture is standard for corrosion protection and
freeze resistance. Total cooling system capacity is 5.0 liters (5.3 US
qt) for the engine side, excluding the radiator and external hose
volume.
Intake System: Consists of an air cleaner (oil bath or dry element) and
a cast iron or aluminum intake manifold. Exhaust System: Comprises a
cast iron exhaust manifold and a downpipe connecting to the equipment's
exhaust silencer.
Electrical System: Operates on a 12V or 24V system. A corresponding
starter motor and alternator or DC generator are fitted. The engine
incorporates a glow plug system for cold starting, controlled by a
key-switch or timer module. An electric stop solenoid or manual cable
acts on the injection pump rack.
Governor: A mechanical centrifugal governor is standard, integrated
within the Bosch PES4-A injection pump. Configurable for variable or
constant-speed operation.
Length (Front Face of Block to Flywheel Housing): 660 mm (25.98 in).
Width (Overall): 515 mm (20.28 in).
Height (Overall, from sump to valve cover): 728 mm (28.66 in).
Dry Weight (with standard accessories): 230 kg (507 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, dependent on operating 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 belts showing signs of wear, glazing,
or cracking. Fuel Injection System Inspection: Have injection pressure,
spray pattern, and pump timing checked by a specialist every 1,500
hours.
Cylinder Head Nuts: Tighten in the specified multi-step crisscross
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/Cartridge: For a canister, tighten the center bolt
to 25-30 Nm (18-22 lb-ft). For a spin-on filter, hand-tighten plus 3/4
turn after gasket contact.
The Mitsubishi S3E engine was applied in a range of medium-duty
industrial, agricultural, and construction equipment where its
three-cylinder balance and dependable indirect injection performance
were advantageous. Common applications include: Agricultural Tractors:
Medium-power utility tractors from Japanese and Asian manufacturers.
Construction Equipment: Mid-sized vibratory rollers, mobile air
compressors, light towers, and concrete pumps. Generator Sets:
Industrial and prime power generator sets in the 20-30 kVA power range.
Pumping Equipment: Large irrigation pumps, industrial transfer pumps,
and firefighting units. Material Handling: Medium-duty forklifts (3-5
ton capacity) and stationary hydraulic power units. Agricultural
Machinery: Powers larger implements such as combine harvesters, balers,
and feed processing equipment. Marine Applications: Used as an auxiliary
generator drive or propulsion engine for small to medium-sized fishing
vessels and workboats.
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