Mitsubishi S12A2 Specifications
| Engine Model: Mitsubishi S12A2 |
| Engine Type: 4-cycle 12-cylinder V-block turbocharged liquid-cooled diesel |
| Total Displacement: 2,071 cu.in (33.93 L) |
| Rated Engine Power: 910-1140 Hp (679-850 kW) at 1500-1800 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi S12A2 is a high-performance,
12-cylinder V-type diesel engine produced by Mitsubishi Heavy Industries
for heavy-duty industrial and marine applications. This engine belongs
to the A-series family and features a 60-degree V-configuration with
turbocharging and aftercooling.
Designed for continuous operation in demanding environments, the S12A2
serves in power generation, maritime propulsion, and industrial drive
applications such as data center backup generators, commercial vessels,
fishing boats, tugboats, and offshore support vessels. The engine
incorporates proprietary Mitsubishi mechanical fuel system and
turbocharger technology, providing economical fuel consumption and a
minimized installation footprint.
The Mitsubishi S12A2 represents a robust engineering solution for
applications requiring sustained power output with high reliability. The
bore and stroke dimensions of 150 mm by 160 mm produce a bore/stroke
ratio of 0.94:1, a near-square configuration balancing torque
characteristics with operational smoothness. The compression ratio
varies between 14.5:1 and 15.3:1 depending on the specific variant,
enabling efficient cold starting and stable combustion under
turbocharged boost pressures.
The pump-line-nozzle fuel injection system utilizes two in-line pumps,
delivering precise fuel metering for each cylinder bank. The engine
incorporates replaceable cylinder liners for simplified overhaul
procedures. With dry weights ranging from 2,920 kg to 4,400 kg depending
on configuration and application, the S12A2 provides necessary
structural rigidity for industrial mounting configurations. The 24-volt
electrical system with two 6.0 kW starter motors ensures reliable
starting in all conditions.
Engine Type: 4-stroke, V-type, turbocharged and aftercooled, diesel.
Engine Code: S12A2 (S12A2-PTA, S12A2-PTA2, S12A2-MPT, S12A2-MPTA).
Configuration: 60-degree V-12, liquid-cooled, direct injection.
Displacement: 33.93 L (33,930 cc / 2,071 cu.in).
Bore: 150 mm (5.91 in).
Stroke: 160 mm (6.30 in).
Bore/Stroke Ratio: 0.94:1 (near-square configuration).
Compression Ratio: 14.5:1 or 15.3:1 depending on variant.
Aspiration: Turbocharged with aftercooler (charge air cooler).
Rated Power (S12A2-PTA, standby, 1,800 rpm): 850 kW (1,140 hp).
Rated Power (S12A2-PTA, standby, 1,500 rpm): 746 kW (1,000 hp).
Rated Power (S12A2-PTA, prime, 1,800 rpm): 761 kW (1,020 hp).
Rated Power (S12A2-PTA, prime, 1,500 rpm): 679 kW (910 hp).
Rated Power (S12A2-PTA2, prime): 764 kW (1,024 hp) at 1,500 rpm.
Rated Power (S12A2-PTA2, standby): 840 kW (1,126 hp) at 1,500 rpm.
Rated Power (S12A2-MPTA): 770 kW (1,040.6 hp) at 1,950 rpm.
Rated Power (S12A2-MPTK): 820 kW (1,100 hp) at 1,600 rpm.
Maximum Torque (S12A2-MPTA): 3,588 Nm (2,646 lb-ft) at 1,425 rpm.
Governed Speed: 1,500 rpm, 1,800 rpm, 1,950 rpm, or 1,600 rpm.
Rotation (ISO 1204): Counter-clockwise.
Emissions Compliance: IMO Tier II, EPA compliant.
The cylinder block is constructed from cast iron with a V-12
configuration at a 60-degree bank angle. This arrangement provides
inherent balance and reduced vibration compared to inline configurations
of equivalent displacement. The block incorporates replaceable cylinder
liners, allowing service overhaul without block replacement. A forged
steel crankshaft operates within the block, supported by main bearings
across the engine length.
The crankcase includes integrated piston cooling oil jets directed at
the underside of each piston crown for thermal management under
high-load operation. The block features mounting provisions for two fuel
injection pumps (one per cylinder bank) driven from the rear gear train.
A ladder frame structure provides additional rigidity for the main
bearing supports.
The cylinder head assembly consists of two separate cylinder heads, one
for each cylinder bank, manufactured from cast iron. The valve train
utilizes an overhead valve configuration with pushrods and rocker arms
actuated by a camshaft located in the cylinder block. Each cylinder
employs two valves: one intake and one exhaust. The direct injection
combustion chamber positions the injector centrally. Valve seats are
induction-hardened for wear resistance in continuous diesel operation.
Valve Clearances (engine cold):
Intake: 0.25 mm (0.010 in)
Exhaust: 0.25 mm (0.010 in)
The fuel system employs a pump-line-nozzle injection system utilizing
two in-line injection pumps, one for each cylinder bank. Pump type is
Bosch P-Type or equivalent. Each pump is driven from the engine rear
gear train. High-pressure injection lines route fuel from each pump to
individual injectors located in each cylinder head.
The system includes primary fuel filters with water separation. Governor
types vary by application and variant, with mechanical governors on
industrial constant-speed versions and electronic governors on marine
propulsion versions. A fuel transfer pump supplies fuel from the tank to
the injection pumps.
The lubrication system is a pressurized, full-flow filtered system with
a gear-type oil pump. The pump draws oil from the sump through a
screened pickup tube. Oil passes through full-flow spin-on filters
mounted on the cylinder block. Pressurized oil routes to the main
bearings, connecting rod bearings, camshaft bearings, and rocker arm
assemblies. Piston cooling jets receive pressurized oil for piston crown
cooling. A pressure relief valve maintains system pressure within
specification.
Total System Oil Capacity: 120 L (31.7 US gal)
Standard Oil Pan (high): 100 L (26.4 US gal)
Standard Oil Pan (low): 80 L (21.1 US gal)
Oil Pressure at Rated RPM (S12A2-MPTA): 200 kPa (29 psi)
Oil Change Interval: 250 hours
Recommended Oil: Diesel-grade meeting manufacturer specifications
The cooling system is pressurized and liquid-cooled with common jacket
water and charge-air cooling circuits. A belt-driven centrifugal water
pump circulates coolant through the cylinder block, cylinder heads, and
aftercooler.
For marine applications, a seawater-cooled heat exchanger system is
employed. For industrial generator applications, a radiator cooling
system is utilized. The charge air cooler reduces intake air temperature
after turbocharging for increased air density and combustion efficiency.
Coolant Capacity (engine only): 100 L (26.4 US gal).
Coolant Capacity (total system, industrial): 215 L (56.8 US gal).
Thermostat Operating Range: 65-85°C (149-185°F).
Coolant Type: Ethylene glycol-based anti-freeze with corrosion
inhibitors (industrial) or freshwater with seawater heat exchanger
(marine).
Electrical System: 24-volt direct current.
Starting System: Two electric starter motors, each 6.0 kW.
Charging System: Alternator, 24V-25A (industrial) ; 24V-60A (marine MPTA
variant).
Turbocharging System: Single or multiple turbochargers with aftercooler.
The turbocharger is Mitsubishi-designed and manufactured.
Aftercooler: Charge air cooler using engine coolant (industrial) or
seawater (marine) as the cooling medium.
Air Intake System: Dry-type replaceable element air cleaner.
Exhaust System: Cast iron exhaust manifolds with coupling connections.
Exhaust manifold coupling nuts tighten to a low torque of 9 ± 0.45 Nm
(6.6 ± 0.3 lb-ft). Exhaust temperature maximum (S12A2-MPTA): 560°C
(1,040°F).
Overall Length (S12A2-PTA industrial): 2,060 mm (81.1 in)
Overall Width (S12A2-PTA industrial): 1,382 mm (54.4 in)
Overall Height (S12A2-PTA industrial): 1,542-1,541 mm (60.7-60.7 in)
Length (S12A2-MPTA marine): 2,440 mm (96.1 in)
Width (S12A2-MPTA marine): 1,471 mm (57.9 in)
Height (S12A2-MPTA marine): 1,480 mm (58.3 in)
Length (S12A2-MPTK): 3,550 mm (139.8 in)
Width (S12A2-MPTK): 1,600 mm (63.0 in)
Height (S12A2-MPTK): 2,100 mm (82.7 in)
Dry Weight (S12A2-PTA industrial): 3,400 kg (7,496 lb)
Dry Weight (S12A2-PTA2 industrial): 2,920 kg (6,438 lb)
Dry Weight (S12A2-MPTA marine): 4,400 kg (9,700 lb)
Dry Weight (S12A2-MPTK marine): 6,500 kg (14,330 lb) without gearbox
Engine Oil Capacity (total system): 120 L (31.7 US gal)
Coolant Capacity (engine only): 100 L (26.4 US gal)
Coolant Type: Ethylene glycol-based with corrosion inhibitors
Oil Change Interval: 250 hours
Service Intervals (marine): Every 500 hours or annually
Valve Clearance (cold, intake): 0.25 mm (0.010 in)
Valve Clearance (cold, exhaust): 0.25 mm (0.010 in)
Oil Pressure (S12A2-MPTA at rated rpm): 200 kPa (29 psi)
Maximum Exhaust Temperature (S12A2-MPTA): 560°C (1,040°F)
Cylinder Head Bolt (short, Type 1): 118 ± 5.9 Nm (87 ± 4.3 lb-ft)
Cylinder Head Bolt (long, Type 1): 196 ± 9.8 Nm (144 ± 7.2 lb-ft)
Cylinder Head Bolt (short, Type 2): 118 ± 5.9 Nm (87 ± 4.3 lb-ft)
Cylinder Head Bolt (long, Type 2): 196 ± 9.8 Nm (144 ± 7.2 lb-ft)
Cylinder Head Bolt (Type 3): 392 ± 20 Nm (289 ± 14.8 lb-ft)
Main Bearing Cap Bolts: 588 ± 29 Nm (434 ± 21 lb-ft)
Main Bearing Cap Side Bolts: 147 ± 7.4 Nm (108 ± 5.5 lb-ft)
Connecting Rod Cap Bolts: 343 ± 17 Nm (253 ± 12 lb-ft)
Flywheel Bolts: 539 ± 27 Nm (397 ± 20 lb-ft)
Damper Bolts: 539 ± 27 Nm (397 ± 20 lb-ft)
Camshaft Gear Bolt: 294 ± 15 Nm (217 ± 11 lb-ft)
Rocker Shaft Bracket Bolts: 49 ± 2.5 Nm (36 ± 1.8 lb-ft)
Rocker Arm Lock Nuts: 64 ± 6.4 Nm (47 ± 4.7 lb-ft)
Bridge Lock Nuts: 55 ± 5.5 Nm (40.5 ± 4.1 lb-ft)
Timing Gear Case Bolts: 34 ± 1.7 Nm (25.3 ± 1.2 lb-ft)
Rear Plate Bolts: 98 ± 4.9 Nm (72 ± 3.6 lb-ft)
Front Mounting Bracket Bolts: 255 ± 12.8 Nm (188 ± 9.4 lb-ft)
Rear Mounting Bracket Bolts: 98 ± 4.9 Nm (72 ± 3.6 lb-ft)
Balance Weight Bolts: 196 ± 10 Nm (145 ± 7.4 lb-ft)
Idler Shaft Bolts: 245 ± 12 Nm (180 ± 8.9 lb-ft)
Idler Gear Thrust Plate Bolts: 54 ± 2.7 Nm (39.8 ± 2.0 lb-ft)
Fuel Injection Pump Gear Bolts: 294 ± 15 Nm (217 ± 11 lb-ft)
Oil Pump Gear Bolts: 294 ± 15 Nm (217 ± 11 lb-ft)
Rocker Cover Bolts: 15 ± 2 Nm (10.9 ± 1.5 lb-ft)
Exhaust Manifold Coupling Nuts: 9 ± 0.45 Nm (6.6 ± 0.3 lb-ft)
The Mitsubishi S12A2 engine series is installed in the following
applications.
Industrial Power Generation:
Data center backup generator sets.
Commercial and municipal building standby power.
Manufacturing plant continuous power.
Distributed power generation systems.
Marine Propulsion:
Commercial vessels including bulk carriers, tankers, and container
ships.
Fishing vessels for high-seas fishing operations.
Tugboats and offshore support vessels.
Passenger ferries and small cruise ships.
Towboats: M/V Dorella Banta (twin S12A2 engines rated 850 hp at 1,940
rpm).
Patrol and workboats.
Industrial Drives:
Pump drives.
Compressor drives.
Crusher and mill drives.
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