Mitsubishi 6DS7 Specifications
| Engine Model: Mitsubishi 6DS7 |
| Engine Type: 4-cycle inline 6-cylinder liquid-cooled diesel |
| Total Displacement: 331.4 cu.in (5.43 L) |
| Rated Engine Power: 135-200 Hp (101-148 kW) at 2600 rpm |
| Fuel System Type: Indirect injection |
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The Mitsubishi 6DS7 is a heavy-duty, inline
6-cylinder diesel engine produced by Mitsubishi Heavy Industries. This
engine served as a common powerplant for medium-duty trucks,
particularly the Fuso FK series, as well as various industrial
applications including cranes, generator sets, and marine vessels during
the 1970s and 1980s. The engine features an indirect injection
combustion system utilizing a swirl chamber, a design choice that
promotes smoother combustion and reduced noise compared to direct
injection engines of the same era.
The naturally aspirated configuration prioritizes mechanical simplicity
and reliability over maximum power output. The robust cast iron
construction, replaceable dry-type cylinder liners, and straightforward
mechanical fuel system contributed to the engine's reputation for
extended service life under sustained heavy loads. A turbocharged
variant, the 6DS7-T, was also produced offering higher power output for
applications demanding increased performance.
The Mitsubishi 6DS7 is a 4-stroke, water-cooled, naturally aspirated,
inline 6-cylinder diesel engine. The inline configuration provides
inherent primary balance due to the even number of cylinders firing at
120-degree intervals.
Engine Type: 4-stroke, water-cooled, inline 6-cylinder, naturally
aspirated diesel.
Displacement: 5.43 L (5,431 cc, 331.4 cu.in).
Bore x Stroke: 98 mm x 120 mm (3.86 in x 4.72 in).
Compression Ratio: 18.0:1.
Maximum Power (Naturally Aspirated): 135 to 145 hp (101 to 108 kW) at
3,200 rpm.
Maximum Power (Turbocharged Marine Variant): 200 hp at 2,600 rpm.
Peak Torque (Naturally Aspirated): 353 Nm (260 lb-ft) at 1,800 rpm.
Firing Order: 1-5-3-6-2-4.
Aspiration: Naturally aspirated. A turbocharged variant (6DS7-T)
equipped with an intercooler was also produced.
Combustion System: Indirect injection with a swirl chamber.
Fuel Injection Timing: 18° to 20° BTDC.
Idling Speed: 550 to 600 rpm (manual transmission applications).
Rotation (flywheel end): Counterclockwise when viewed from the front of
the engine.
The cylinder block is constructed from high-strength cast iron with a
deep-skirt design that extends below the crankshaft axis. The block
houses seven main bearing bulkheads supporting the forged steel or
nodular cast iron crankshaft. The cylinder bores utilize replaceable
dry-type cylinder liners pressed into the parent block material.
The dry liner design eliminates coolant contact with the liner exterior,
reducing cavitation erosion risks. The block includes machined mounting
surfaces for the fuel injection pump on the side and the flywheel
housing at the rear. A pressed steel oil pan bolts to the lower flange.
The cylinder head is a single-piece, cast-iron cross-flow unit spanning
all six cylinders. The overhead valve (OHV) configuration places the
camshaft within the cylinder block. Pushrods transfer motion from the
camshaft to the rocker arms. Two valves per cylinder (one intake, one
exhaust) produce a total of 12 valves. Valve seats are pressed-in, with
intake seats constructed of wear-resistant iron alloy and exhaust seats
of heat-resistant steel alloy.
Valve guides are press-fit. The valvetrain uses mechanical lash
adjusters (screw and locknut type) requiring periodic manual valve
clearance inspection. The cylinder head gasket is a composite
construction with steel fire rings at each cylinder bore.
The fuel system is a mechanical indirect injection design utilizing a
swirl chamber (pre-combustion chamber) in the cylinder head. An in-line
injection pump (Bosch P-type or Mitsubishi licensed equivalent) is
mounted on the side of the cylinder block and driven by the engine gear
train. The pump features one plunger and barrel assembly per cylinder.
A mechanical centrifugal governor integrated into the pump housing
regulates engine speed by controlling the fuel rack position. A
gear-type transfer pump draws fuel through a primary fuel filter with a
water separator. High-pressure fuel lines route fuel from the injection
pump to six mechanical injectors, one per cylinder. Each injector
delivers fuel into the swirl chamber, where partial combustion occurs
before flame propagates into the main combustion chamber in the piston
crown.
The lubrication system is a fully pressurized, forced-feed circuit. A
gear-type oil pump, driven from the crankshaft nose, draws oil through a
strainer from a pressed steel sump. Oil capacity varies depending on the
oil pan depth, which differs by chassis application. Oil passes through
a full-flow spin-on canister filter before distribution. A bypass valve
opens if the filter becomes restricted. A water-cooled oil cooler is
integrated into the system for marine and high-load industrial
applications.
Oil Capacity: 11.0 to 13.0 L (11.6 to 13.7 qt), dependent on oil pan
configuration.
Oil Pressure (rated speed, warm engine): 350 to 450 kPa (51 to 65 psi).
Recommended Oil Grade: SAE 15W-40 for temperate climates, or SAE 30 for
sustained high ambient temperatures above 30°C (86°F). API
classification CD or higher.
The cooling system is a pressurized, sealed, thermostatically controlled
circulation circuit. A belt-driven centrifugal water pump circulates
coolant through the cylinder block and cylinder head. A wax-pellet
thermostat located in a housing at the front of the cylinder head
regulates coolant flow. A bypass circuit permits coolant circulation
within the engine during warm-up. For marine applications, a heat
exchanger replaces the radiator with a raw water cooling circuit.
Engine Coolant Capacity: Approximately 12.0 L (12.7 qt), engine only,
without radiator.
Thermostat Opening Temperature: 76°C to 82°C (169°F to 180°F).
Thermostat Fully Open Temperature: 95°C (203°F).
Recommended Coolant: Ethylene glycol antifreeze mixed 50% with distilled
water.
Electrical System: 24-volt negative ground. A 24V starter motor rated at
3.7 kW or 5.0 kW is standard equipment. A 24V alternator with 25 to 35
amp output charges two 12-volt batteries connected in series.
Starting Aid: An intake air heater (thermostart flame-type) for cold
climates. Activation is automatic below 5°C (41°F) or via a manual
push-button on the instrument panel.
Governor: Mechanical, centrifugal-type governor integrated into the
in-line injection pump. Provides speed control from idle to maximum
rated load.
Air Cleaner: Dry-type, single-stage or two-stage paper element filter
with a dust evacuation valve.
Exhaust System: Single exhaust manifold with a 4-inch (102 mm) diameter
outlet flange. A muffler is standard for truck and industrial
applications.
Dry Weight (without flywheel, starter, or alternator): 500 kg (1,102
lb).
Overall Length (front pulley to flywheel face): 1,100 mm (43.3 in).
Overall Width (exhaust manifold outer to injection pump outer): 650 mm
(25.6 in).
Overall Height (oil pan bottom to rocker cover top): 850 mm (33.5 in).
Oil Change Interval: 5,000 km (3,100 mi) or 150 hours for truck
operation. Reduce to 2,500 km (1,550 mi) or 75 hours for severe
conditions such as dusty environments or sustained high ambient
temperatures. Oil Filter Replacement: At every oil change. Fuel Filter
Replacement (primary): 5,000 km (3,100 mi). Drain water separator
weekly. Fuel Filter Replacement (secondary): 10,000 km (6,200 mi).
Valve Clearance (cold engine, mechanical lash adjusters): Intake: 0.30
mm (0.0118 in). Exhaust: 0.30 mm (0.0118 in). Inspect and adjust every
10,000 km (6,200 mi) or 250 hours. Injection Timing Check: 18° to 20°
BTDC. Verify using a timing light and dynamic timing meter every 20,000
km (12,400 mi) or after injection pump removal. Injector Service
Interval: Test crack pressure and spray pattern every 10,000 km (6,200
mi). Replace nozzle tips at 20,000 km (12,400 mi).
Air Cleaner Service: Replace primary element when restriction indicator
shows 6.2 kPa. Maximum element life 20,000 km (12,400 mi) in normal
conditions. Coolant Replacement: 40,000 km (25,000 mi) or 2 years. Drive
Belt (fan/alternator): Inspect for cracks or glazing at 5,000 km (3,100
mi). Replace at 10,000 km (6,200 mi). Starter Motor Inspection: Clean
commutator and check brush length at 50,000 km (31,000 mi). Minimum
brush length: 10 mm (0.39 in).
Cylinder Head Bolts: 175 to 185 Nm (129 to 136 lb-ft).
Connecting Rod Cap Nuts: 95 to 105 Nm (70 to 77 lb-ft).
Main Bearing Cap Bolts: 195 to 210 Nm (144 to 155 lb-ft).
Flywheel Bolts: 185 to 200 Nm (136 to 148 lb-ft).
Flywheel Housing Bolts (to block): 65 lb-ft (88 Nm).
Crankshaft Pulley Bolt (center): 150 Nm (111 lb-ft).
Camshaft Thrust Plate Bolts: 18 Nm (13 lb-ft).
Rocker Arm Shaft Bracket Bolts: 40 Nm (30 lb-ft).
Rocker Arm Adjusting Locknut: 25 Nm (18 lb-ft).
Valve Cover Nuts: 8 Nm (6 lb-ft).
Injection Pump Mounting Nuts: 35 Nm (26 lb-ft).
Injection Pump Drive Gear Bolt: 55 Nm (41 lb-ft).
Injector Hold-Down Clamp Bolts: 30 Nm (22 lb-ft).
Injector Nozzle Holder Assembly (to cylinder head): 70 Nm (52 lb-ft).
High-Pressure Fuel Line Nuts: 30 Nm (22 lb-ft).
Oil Pump Mounting Bolts: 18 Nm (13 lb-ft).
Water Pump Mounting Bolts: 25 Nm (18 lb-ft).
Thermostat Housing Bolts: 18 Nm (13 lb-ft).
Starter Motor Mounting Bolts: 50 Nm (37 lb-ft).
Alternator Pivot Bolt: 40 Nm (30 lb-ft).
Exhaust Manifold Nuts: 30 Nm (22 lb-ft).
The Mitsubishi 6DS7 engine served in a wide range of vehicle,
industrial, and marine applications across global markets.
Medium-Duty Trucks: The engine was a standard powerplant for the
Mitsubishi Fuso FK series trucks, including models such as the FK415,
FK417, and FK419. These 4x2 rigid trucks were used for distribution,
freight transport, and municipal services.
Buses: Small to medium buses including the Mitsubishi Rosa and certain
Fuso bus chassis models.
Industrial Equipment: The naturally aspirated 6DS7 was used in
stationary generator sets rated at 80 to 100 kVA for prime or standby
power. The engine also powered industrial air compressors, hydraulic
power units, and crane carrier vehicles.
Construction Machinery: Certain models of Mitsubishi excavators and
wheel loaders received the 6DS7 engine.
Marine Propulsion: The turbocharged and intercooled variant (6DS7-T) was
adapted for marine use. A listing for a reconditioned marine engine
indicates 200 hp at 2,600 rpm with a heat exchanger and 1.5:1 gearbox
ratio. These engines were used in small fishing vessels, workboats, and
leisure craft requiring reliable diesel propulsion.
Agricultural Equipment: Large tractors and self-propelled agricultural
implements including combine harvesters and forage harvesters used the
6DS7 in certain markets.
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