Mitsubishi S12R Specifications
| Engine Model: Mitsubishi S12R |
| Engine Type: 4-cycle 12-cylinder V-block turbocharged liquid-cooled diesel |
| Total Displacement: 2992 cu.in (49.03 L) |
| Rated Engine Power: 1140-1904 Hp (850-1420 kW) at 1500-1800 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi S12R is a 12-cylinder, V-type
diesel engine engineered for heavy-duty industrial and marine
applications where high displacement and continuous operation are
required. Produced by Mitsubishi Heavy Industries Engine System Asia,
this engine is widely deployed in large-scale power generation, ship
propulsion, and auxiliary generator sets. The S12R platform employs a
60° V configuration with a long-stroke design that maintains a compact
footprint while substantially increasing power output compared to lower
displacement engines.
Mitsubishi offers multiple sub-variants including the S12R-PTA and
S12R-PTAA2, distinguished by their cooling circuit configurations and
power ratings. The engine operates on a mechanical pump-line-nozzle fuel
system , providing field serviceability without proprietary electronic
diagnostic equipment. Each cylinder head is individually removable,
simplifying maintenance access for large-bore V-configuration engines.
This engine is certified to EPA Tier 3 and IMO Tier II emission
standards for marine applications.
The S12R follows Mitsubishi’s V12 architecture with a 60° cylinder bank
angle, balancing smooth operation with structural rigidity. The
long-stroke design (180 mm stroke vs 170 mm bore) favors torque
production for low-speed propulsion and generator drive applications.
Engine Type: 4-cycle, water-cooled, 60° V-type diesel
Number of Cylinders: 12
Total Displacement: 49.03 L (2992 cu.in)
Bore x Stroke: 170 mm x 180 mm (6.69 in x 7.09 in)
Compression Ratio: 14.0:1 to 14.5:1 depending on sub-model and
application
Firing Order: 1-12-5-8-3-10-6-7-2-11-4-9
Rotation (ISO 1204): Counter-clockwise
Rated Speed (Generator): 1500 rpm (50 Hz) or 1800 rpm (60 Hz)
Marine Propulsion Power Range: 850 kW to 1420 kW (1140-1904 hp)
Generator Power Range (Standby): 1100 kVA to 1600 kVA
Low Idle Speed: 600-650 rpm
Aspiration: Turbocharged with intercooler (MPTK) or aftercooler
(PTA/PTAA2)
The cylinder block is constructed from high-grade cast iron with a 60° V
configuration, eliminating the need for separate cylinder banks. The
deep-skirt crankcase design surrounds the main bearing journals,
providing structural reinforcement for the large-bore configuration.
Seven main bearings support the forged steel crankshaft. Replaceable
wet-type cylinder liners are fitted, extending overhaul capability
without block replacement.
The liners are sealed at the lower end by O-rings and at the upper end
by the cylinder head gasket. Water jacket passages surround each liner
uniformly, managing thermal gradients across the full 180 mm stroke
length. The block incorporates a front-mounted gear train housing that
drives the camshafts, fuel injection pumps, and auxiliary equipment.
This engine design uses individual cylinder heads for each cylinder,
simplifying removal and installation during maintenance.
The Mitsubishi S12R features individual cylinder heads for each of the
12 cylinders, constructed from cast iron with a cross-flow port design.
This arrangement permits removal of a single cylinder head without
disturbing adjacent cylinders, reducing downtime for valve service or
injector access.
Each cylinder head accommodates four valves: two intake and two exhaust,
operated by a single overhead camshaft per cylinder bank. Valve seats
are pressed-in alloy inserts, replaceable during head overhaul. The
overhead camshaft arrangement eliminates pushrods, providing stable
valve actuation across the engine’s speed range.
Valve Clearance (cold, intake): 0.40 mm (0.0157 in)
Valve Clearance (cold, exhaust): 0.50 mm (0.0197 in)
The fuel system uses a mechanical pump-line-nozzle configuration with
two in-line injection pumps mounted at the front of the engine. The PS6
type injection pump is gear-driven from the engine timing case. Each
pump supplies fuel to six cylinders through high-pressure lines of equal
length. Individual injection nozzles are positioned centrally in each
cylinder head, producing a multi-hole spray pattern for direct injection
combustion.
No electronic control is present on standard configurations; fuel
delivery is governed by a mechanical or electronic governor depending on
application. A gear-type transfer pump draws fuel from the tank through
a replaceable filter with water separator. Excess fuel returns to the
tank through a bypass line.
Fuel Injection Timing: 7.5° BTDC for generator drive variants
Maximum Inlet Resistance (Transfer Pump): 75 mm Hg
Maximum Return Resistance: 150 mm Hg
The lubrication system is a pressurized wet-sump configuration with
forced feed to all bearing surfaces. Multiple gear-type oil pumps are
mounted within the front timing case. Oil is drawn through a strainer
from the sump, passed through a full-flow replaceable spin-on filter,
and fed to the main oil gallery.
The gallery distributes oil to the crankshaft main bearings, connecting
rod bearings, camshaft bearings, and rocker shafts. Piston cooling jets,
directed at the underside of each piston crown, manage thermal loads
under sustained high-power operation. A plate-type oil cooler,
water-cooled, maintains lubricant temperature within operational limits.
The oil pan is fabricated from welded steel.
Total Oil Capacity (including filters): 180 L (47.5 gal)
Oil Pressure at Rated Speed: 0.49-0.64 MPa (71-93 psi)
Oil Pressure at Idle Speed: 0.20-0.30 MPa (29-44 psi)
Maximum Oil Temperature (oil pan): 110°C (230°F)
Recommended Oil Grade: API CD or CF, SAE 30 or SAE 40
The cooling system uses a water-cooled configuration with separate
cooling circuits depending on the sub-variant. For S12R-PTA models,
common jacket water and charge-air cooling circuits share a coolant
loop. For S12R-PTAA2 and marine MPTK variants, separate jacket water and
charge-air cooling circuits with seawater-cooled heat exchangers are
employed.
A centrifugal water pump, belt-driven from the front accessory drive,
circulates coolant through the block water jackets, cylinder heads, and
aftercooler core. A thermostat, rated at 71-85°C (160-185°F), regulates
coolant flow to the external radiator or heat exchanger. A coolant
expansion tank accommodates thermal volume changes.
Coolant Capacity (engine only): 125 L (33.0 gal).
Total Cooling System Capacity: 368 L (97.2 gal) including external
circuits.
Maximum Engine Outlet Water Temperature: 98°C (208°F).
Maximum Coolant Intercooler Inlet Temperature: 10°C (18°F) above ambient
for seawater-cooled variants.
| Intake and Exhaust Systems |
Air Intake System: Dry-type replaceable paper element air cleaner with a
restriction indicator. The turbocharger is a Mitsubishi-designed fixed
geometry unit. For PTAA variants, an air-to-air aftercooler reduces
intake air temperature after compression. For MPTK and PTA variants, a
water-cooled intercooler or aftercooler is employed.
Exhaust System: Dry exhaust manifold with water-cooled sections for
marine configurations. Maximum exhaust back pressure is limited in
generator applications. Maximum allowable exhaust temperature at
turbocharger outlet is 650°C (1200°F).
Electrical System: 24-volt starting system with dual 7.5 kW starters.
Alternator output is 24-30 V, 50-120 amperes depending on specification.
Glow plugs or intake air heaters are not required for cold start in most
temperate climates due to high compression ratio.
Governor: Electronic governor standard for generator applications,
providing isochronous speed regulation with droop options for load
sharing. Mechanical governor available for certain propulsion
configurations.
Starting Aid: Air start system available for larger marine
installations; electric start (24V) standard for generator sets.
Length (flywheel housing to front pulley): 2491-2571 mm (98.1-101.2 in)
Width: 1360-1622 mm (53.5-63.9 in)
Height: 1592-1728 mm (62.7-68.0 in)
Dry Weight (S12R-PTA): 5350 kg (11,795 lb)
Dry Weight (S12R-PTAA2): 5300-5400 kg (11,685-11,905 lb)
Dry Weight (S12R-MPTK Marine): 5500 kg (12,125 lb)
Oil Change Interval: 500 hours under normal industrial/marine duty.
Oil Change Interval: 250 hours under severe or high-load operation.
Recommended Oil Grade: SAE 30 or SAE 40 meeting API CD or CF.
Oil Filter Change: Replace both filters at every oil change.
Fuel Filter Element Change Interval: 500 hours or annually.
Valve Lash Inspection Interval: 1000 hours.
Intake Valve Lash: 0.40 mm (0.016 in).
Exhaust Valve Lash: 0.50 mm (0.020 in).
Coolant Change Interval: 2000 hours or 2 years.
Coolant Type: Heavy-duty diesel antifreeze with supplemental coolant
additive.
Air Cleaner Element Service: Replace when restriction indicator signals.
Injector Inspection Interval: 2000 hours.
Injector Cracking Pressure (nozzle): 180-200 bar (2610-2900 psi).
Turbocharger Inspection Interval: 2000 hours for bearing play and wheel
condition.
Cylinder Liner Protrusion Above Block Deck: 0.05-0.10 mm (0.0020-0.0039
in).
Maximum Installation Inclination Angle (Standard Oil Pan): 6.5°
front/rear tilt; 22.5° heel.
Cylinder Head Bolts: 490-539 Nm (361-398 lb-ft)
Connecting Rod Cap Bolts: 441-490 Nm (325-361 lb-ft)
Main Bearing Cap Bolts: 686-735 Nm (506-542 lb-ft)
Flywheel Bolts (to crankshaft flange): 441-490 Nm (325-361 lb-ft)
Flywheel Housing to Block Bolts: 220-250 Nm (162-184 lb-ft)
Camshaft Bearing Caps: 70-80 Nm (52-59 lb-ft)
Injector Clamp Nuts: 25-30 Nm (18-22 lb-ft)
High-pressure Fuel Line Fittings (pump end): 30-35 Nm (22-26 lb-ft)
High-pressure Fuel Line Fittings (nozzle end): 18-22 Nm (13-16 lb-ft)
Valve Cover Bolts: 20-25 Nm (15-18 lb-ft)
Oil Pan Bolts (M12): 40-50 Nm (30-37 lb-ft)
Thermostat Housing Bolts: 20-25 Nm (15-18 lb-ft)
Intake Manifold Bolts: 35-45 Nm (26-33 lb-ft)
Exhaust Manifold Nuts: 70-85 Nm (52-63 lb-ft)
Turbocharger Mounting Nuts: 70-85 Nm (52-63 lb-ft)
Front Crankshaft Pulley Bolt: 800-900 Nm (590-664 lb-ft)
Rocker Shaft Bracket Bolts: 70-80 Nm (52-59 lb-ft)
The Mitsubishi S12R serves across marine propulsion, power generation,
and heavy industrial sectors.
Marine Propulsion (S12R-MPTK): Primary power for towboats, tugboats,
fishing vessels, and workboats in the 1100-1350 hp range at 1600-1800
rpm. Mechanical fuel system provides field serviceability for commercial
fleets operating in remote regions. The new 1350 hp rating is designed
for 2600-2800 hp twin-engine configurations in towboat applications.
Marine Auxiliary (S12R-PTA-C, PTAA2-C): Generator drive engines for
shipboard electrical power, rated 1080-1277 kW at 1500 rpm. Used in
large cargo vessels, tankers, and passenger ships. Configurations
include water-air intercooler (PTA-C) and air-air intercooler (PTAA2-C)
variants.
Generator Sets (Industrial): Stationary standby and prime power
generators for data centers, commercial buildings, municipal facilities,
and distributed power applications. Ratings from 1080 kW (PRP) to 1404
kW (standby) at 1500 rpm. The S12R-PTA and S12R-PTAA2 industrial engines
feature compact footprints for simplified installation.
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