Mitsubishi S6R2 Specifications
| Engine Model: Mitsubishi S6R2 |
| Engine Type: 4-cycle inline 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 1828.4 cu.in (29.9 L) |
| Rated Engine Power: 590-1018 Hp (440-759 kW) at 1500 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi S6R2 is a heavy-duty, 6-cylinder
diesel engine within the SR-Series, recognized for its "long-stroke"
design which significantly increases power output while maintaining a
compact footprint. It is primarily used for marine propulsion, auxiliary
power, and industrial generator sets. Designed and built in Japan, the
engine integrates Mitsubishi’s proprietary turbocharger technology and a
mechanical fuel system to deliver balanced performance, reliability, and
optimal fuel consumption.
The architecture features individual cylinder heads for each cylinder,
simplifying maintenance access and gasket replacement. This engine is
engineered to provide highly reliable operation for demanding
applications such as tugboats, ferries, workboats, and data center
generator sets.
Engine Type: 4-cycle, water-cooled, in-line 6-cylinder diesel engine
Combustion System: Direct injection
Aspiration: Turbocharged with air-cooler (Intercooler/Aftercooler)
Total Displacement: 29.96 liters (1828.4 cu.in)
Bore x Stroke: 170 mm x 220 mm (6.69 in x 8.66 in)
Compression Ratio: 14.0:1 or 14.1:1
Firing Order: 1-5-3-6-2-4
Rotation (ISO 1204): Counter clockwise (as viewed from flywheel)
Flywheel Housing Spec: SAE 18" / SAE No.0
Power Output (Marine Propulsion): 440-759 kW (590-1018 hp)
Power Output (Generator Drive): 635 kW (prime power) at 1500 rpm
Engine Speed (Propulsion): 1350 rpm to 1500 rpm
Idle Speed: 600 rpm to 650 rpm
The cylinder block is constructed from high-strength cast iron,
utilizing a long-stroke design to maximize torque output without
increasing engine width. The block features a crankcase with a ladder
frame configuration to enhance structural rigidity and reduce
vibrations. It houses removable cylinder liners (wet type), which allow
for rebuilds without replacing the entire block.
The crankshaft is supported by multiple main bearings, designed to
withstand the high cylinder pressures generated by the large 220 mm
stroke. The crankcase includes piston cooling oil jets that direct
lubricant to the underside of the piston crowns for thermal management.
The engine utilizes individual cylinder heads for each cylinder, a
significant design feature that simplifies gasket replacement and
inspection compared to a single monolithic head. Each cylinder head is
manufactured from cast iron and houses 4 valves (2 intake, 2 exhaust)
arranged in a cross-flow pattern.
The valve mechanisms include rocker arms, bridge pieces, and pushrods
driven from the camshaft. The valvetrain is equipped with valve rotators
on the exhaust valves to prevent carbon build-up and ensure even heat
distribution.
The fuel system uses a mechanical pump-line-nozzle (PLN) injection
architecture. The system comprises a Mitsubishi PS6 type in-line
injection pump driven by the engine gear train, high-pressure fuel
lines, and multi-hole injection nozzles. The injection pump governor
maintains stable engine speed under varying loads.
The system is timed relative to the crankshaft position, with injection
timing specified at 7.5° BTDC for the generator drive variant
(S6R2-PTA-C). Fuel treatment is handled by primary and secondary
filters, with a priming pump provided to bleed air from the system after
filter changes.
The lubrication system is a forced-feed, wet-sump design utilizing a
gear-type pump mounted to the crankshaft. The system is equipped with a
full-flow oil filter. The oil pan capacity varies based on the
application standard sump capacity ranges from 52 liters (low) to 84
liters (high), with the full system (including filters) holding 94
liters (24.8 gal).
The system features an oil cooler to regulate lubricant temperature.
Operating oil pressure ranges from 0.20 MPa to 0.30 MPa at idle,
increasing to 0.49 Mpa-0.64 Mpa at rated speed. The maximum permissible
oil temperature at the oil pan outlet is 110°C (230°F).
The cooling system is a pressurized, water-cooled system utilizing a
heat exchanger configuration for marine applications. The engine employs
a dual-circuit cooling method: a fresh water (engine coolant) circuit
cools the engine block and cylinder heads, while raw sea water is used
to cool the charge air and the fresh water via a heat exchanger.
The thermostat temperature adjustment range is 71°C to 85°C (160°F to
185°F). The engine-only coolant capacity is 55 liters (14.5 gal), while
the total system can reach 150 liters (39.6 gal) depending on the
radiator or keel cooler configuration.
Timing Drive: The camshaft and fuel injection pump are driven by a
front-mounted gear train. All timing gears are machined steel,
eliminating the need for belts or chains.
Charging System: A belt-driven alternator (24V-30A performance) provides
charging capability for the vessel's or facility's battery banks.
Air Intake System: Intake air is filtered through a dry-type air
cleaner. The air is then compressed by the turbocharger and cooled by a
separate air-to-air or sea water-fed charge air cooler before entering
the cylinders.
Exhaust System: The turbocharger is cooled by the engine's cooling
circuit. The exhaust manifold is designed to route gases efficiently to
the turbocharger turbine inlet.
Governor: An isochronous or droop mechanical governor (integral to the
injection pump) controls engine speed, suitable for constant-speed
generator operation or variable-speed propulsion.
Overall Length: 1,946 mm to 2,455 mm (76.6 in to 96.7 in) depending on
flywheel housing configuration.
Overall Width: 1,051 mm to 1,720 mm (41.4 in to 67.7 in).
Overall Height: 1,578 mm to 1,739 mm (62.1 in to 68.5 in).
Dry Weight (Base Engine): Ranges from 2,870 kg to 3,130 kg (6,327 lb to
6,900 lb) depending on the specific variant (Industrial vs. Marine) and
accessory fitment.
Engine Oil Change: 250-500 operating hours depending on oil analysis.
Engine Oil Filter Change: At every oil change.
Engine Oil Capacity (System): 94 liters (24.8 gal) including filter.
Recommended Oil Grade: SAE 15W-40 (API CF, CF-4, or higher).
Fuel Filter Replacement: 500 operating hours or annually.
Air Filter Element Replacement: When restriction indicator shows or
1,000 hours.
Coolant Replacement: 2,000 operating hours or 2 years.
Coolant Capacity (Engine only): 55 liters (14.5 gal).
Valve Clearance (Cold): Intake: 0.40 mm (0.0157 in); Exhaust: 0.50 mm
(0.0197 in).
Valve Clearance Inspection: 500 operating hours; adjust as required.
Injector Service: 1,000-1,500 operating hours inspection and
calibration.
Injection Pump Timing: Inspect following any pump removal or drive gear
disturbance.
Drive Belt (Accessory) Inspection: 250 operating hours.
Turbocharger Inspection: 2,000 operating hours.
Oil Analysis: Recommended every 250 operating hours for condition
monitoring.
Cylinder Head Bolts (M22x2.5): 539 ± 27 Nm (398 ± 20 lb-ft).
Priming Pump Lock Nut: 8.8 ± 1.0 Nm (6.5 ± 0.7 lb-ft).
Fuel Filter Air Vent Plug: 15 ± 2 Nm (11.1 ± 1.5 lb-ft).
Main Bearing Cap Bolts (M22x2.5): 490 ± 24.5 Nm (361 ± 18 lb-ft).
Connecting Rod Cap Bolts (M22x1.5): Torque-angle method (294 Nm snug
torque).
Flywheel Bolts (M22x1.5): 539 ± 27 Nm (398 ± 20 lb-ft).
The Mitsubishi S6R2 is utilized across marine, industrial, and generator
drive sectors.
Marine Propulsion: Tugboats, ferries, workboats, and towboats (e.g., M/V
Larry Gravely using twin 803 hp S6R2 engines).
Commercial Vessels: Fishing vessels and coastal freighters.
Industrial Power: Generator sets for data centers, municipal buildings,
manufacturing plants, and distributed power.
Agricultural / Industrial Machinery: Large irrigation pumps and
heavy-duty industrial compressors.
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