Mitsubishi 6D15 Specifications
| Engine Model: Mitsubishi 6D15 |
| Engine Type: 4-cycle inline 6-cylinder liquid-cooled diesel |
| Total Displacement: 422 cu.in (6.92 L) |
| Rated Engine Power: 155-160 Hp (115-119 kW) at 2800 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi 6D15 is a 6.9-liter, inline
6-cylinder diesel engine produced by Mitsubishi Motors Corporation. This
powerplant is a highly versatile unit commonly found in medium-duty
commercial vehicles and heavy machinery. The 6D15 belongs to the
D-series engine family, known for its robust cast iron construction,
direct injection combustion, and long service life.
Primary applications include Mitsubishi Fuso FM series trucks, where the
engine provides the torque characteristics required for urban and
regional freight transport. The engine also appears in heavy machinery
from manufacturers such as Kato and Kobelco, powering excavators,
cranes, and other earthmoving equipment.
The Mitsubishi 6D15 employs a direct injection combustion system, which
delivers better fuel efficiency compared to indirect injection designs
of similar displacement. The overhead valve (OHV) valvetrain with
pushrods and rocker arms provides a simple, serviceable architecture.
The engine is naturally aspirated in most configurations, though
turbocharged variants exist within the 6D15 family. Operators value this
engine for its reliability, parts availability across Mitsubishi Fuso
dealer networks, and the high torque rise at low engine speeds, which
provides good lugging ability under load.
Engine Type: 4-stroke, inline 6-cylinder, water-cooled diesel.
Aspiration: Naturally aspirated (factory standard; turbocharged variants
available).
Displacement: 6.919 L (6,919 cc / 422 cu.in).
Bore: 113.0 mm (4.45 in).
Stroke: 115.0 mm (4.53 in).
Compression Ratio: 17.5:1.
Combustion System: Direct injection.
Firing Order: 1-5-3-6-2-4.
Rotation (viewed from front): Clockwise.
Maximum Power: 115-119 kW (155-160 hp) at 2,800 rpm.
Maximum Torque: 412 Nm (304 lb-ft) at 1,400-1,600 rpm.
Compression Pressure (std): 30 kg/cm2 (427 psi) at 200 rpm cranking
speed.
Compression Pressure (service limit): 24 kg/cm2 (341 psi) at 200 rpm.
Compression Difference Between Cylinders (maximum): 3 kg/cm2 (43 psi).
Idle Speed: 600-650 rpm.
Rated Speed (truck): 2,800 rpm.
Rated Speed (industrial): 2,600 rpm (continuous), 2,800 rpm
(intermittent).
The cylinder block of the 6D15 is manufactured from high-strength cast
iron with an inline 6-cylinder configuration. This material provides
high rigidity, excellent vibration damping, and resistance to wear in
high-mileage commercial vehicle service. The block design incorporates a
deep-skirt crankcase, where the cylinder walls extend below the
crankshaft centerline, adding structural support for the rotating
assembly.
The cylinder bores are machined directly into the parent cast iron
material; the 6D15 does not use replaceable cylinder liners. Bore
surfaces are induction-hardened to improve wear resistance and
plateau-honed to optimize oil retention for piston ring sealing. The
block houses a 7-main-bearing crankshaft (one main bearing between each
cylinder plus front and rear units). Each main bearing cap is secured by
two bolts.
The crankcase is designed with an integrated oil pan rail, providing a
flat sealing surface for the pressed steel oil pan. The block contains
the mounting pad for the fuel injection pump, mounted on the right side
(viewed from front) and driven by a gear train at the front of the
engine. Coolant passages within the block direct water flow from the
water pump inlet upward toward the cylinder head. The left side of the
block carries the oil filter assembly and the fuel feed pump. The right
side provides the mounting points for the starter motor.
The cylinder head is a single cast-iron component covering all six
cylinders. The use of cast iron for both block and head ensures uniform
thermal expansion rates, reducing head gasket stress. The head employs a
cross-flow design with intake ports on one side and exhaust ports on the
opposite side. The combustion chamber is of the direct injection type,
with a shallow recess machined into the piston crown rather than the
cylinder head.
Valvetrain Configuration: Overhead valve (OHV), pushrods, rocker arms.
Valves per Cylinder: 2 (one intake, one exhaust).
Total Valves: 12.
Intake Valve Diameter: 46.0 mm (1.81 in).
Exhaust Valve Diameter: 40.0 mm (1.57 in).
Valve Stem Diameter: 9.0 mm (0.354 in).
Valve Seat Inserts: Hardened steel, pressed into the cylinder head.
Camshaft Position: In-block (camshaft located within the cylinder block,
driven by gears).
Valve Lash Adjustment: Screw and locknut on rocker arms.
The cylinder head incorporates a centrally located injector bore for
each cylinder, positioning the fuel injector nozzle directly above the
piston crown. Valve seats are induction-hardened for extended life under
continuous high-load operation. The valve train uses pushrods and rocker
arms. The camshaft is mounted within the cylinder block, driven by a
gear train from the crankshaft.
Cam lobes actuate mechanical lifters (flat tappets), pushrods travel
upward to rocker arms, and rocker arms press down on the valve stems.
The rocker shaft is supported on multiple pedestals bolted to the
cylinder head. Valve clearance is adjusted by loosening the rocker arm
locknut and turning the adjusting screw.
Cold Valve Clearance:
Intake Valves: 0.40 mm (0.016 in).
Exhaust Valves: 0.40 mm (0.016 in).
Valve Timing Events:
Intake Valve Opens: 20° BTDC.
Intake Valve Closes: 48° ABDC.
Exhaust Valve Opens: 52° BBDC.
Exhaust Valve Closes: 16° ATDC.
Valve Overlap: 36° (exhaust closing 16° ATDC, intake opening 20° BTDC).
The fuel system is a direct injection design using an in-line injection
pump with a mechanical governor. The system is calibrated for commercial
vehicle duty cycles, prioritizing reliability, fuel economy, and ease of
service.
Fuel System Type: Direct injection (DI) with in-line pump.
Injection Pump Type: Mitsubishi in-line, 6-cylinder, with mechanical
governor.
Injection Pump Model: Bosch P-series or Mitsubishi proprietary
(MITSUBISHI 6D15-1A pump).
Injection Pressure (nozzle opening): 150-160 bar (2,176-2,321 psi).
Injection Timing (static, standard): 17° BTDC (check engine data plate
for exact specification).
Injector Type: Pencil-type with multi-hole nozzle (4-5 holes, 0.25-0.30
mm diameter).
Injector Opening Pressure (new): 150 bar (2,176 psi).
Injector Opening Pressure (service limit): 135 bar (1,958 psi).
Injection Order: 1-5-3-6-2-4.
Fuel Filtration: Primary (water separator) and secondary (spin-on,
10-micron) filters.
The in-line injection pump has a separate pumping element (plunger and
barrel) for each cylinder. Pumping elements are arranged in a line, each
driven by a camshaft within the pump housing. The mechanical governor
(centrifugal flyweight type) maintains engine speed under varying loads
and includes idle and maximum speed limiting functions. A fuel shut-off
lever provides manual emergency shutdown. The pump is mounted to the
cylinder block and driven by a gear train from the crankshaft.
The engine may be equipped with glow plugs for cold-start assistance in
colder climates, though direct injection diesels of this era rely more
heavily on intake air heating grids rather than glow plugs in the
combustion chamber.
The lubrication system is a full-pressure design using a gear-type oil
pump mounted inside the oil pan and driven by the crankshaft. The pump
draws oil through a fixed wire-mesh strainer and pushes it through a
full-flow spin-on oil filter before distribution to the engine's main
oil gallery.
Oil Capacity (standard sump): 12.0 L (12.7 qt).
Oil Capacity (deep sump, truck applications): 14.0 L (14.8 qt).
Oil Pressure at Rated Speed (warm): 3.0-4.0 bar (44-58 psi).
Oil Pressure at Idle (warm, minimum): 0.8 bar (12 psi).
Oil Pressure Relief Valve Setting: 4.5 bar (65 psi).
Oil Pump Type: Gear-type (external spur gears).
Oil Filter Type: Full-flow, spin-on (two filters on some
configurations).
Recommended Oil Viscosity (ambient above 0°C): 15W-40, API CD, CE, or
CF.
Recommended Oil Viscosity (cold climates): 10W-30 or 5W-30.
Oil Change Interval (truck service): 10,000 km (6,200 miles) or 250
hours.
The main oil gallery runs the full length of the cylinder block,
delivering oil to the seven main bearings. Oil reaches the connecting
rod bearings through drilled passages in the crankshaft. Camshaft
bearings and valve train components (lifters, pushrods, rocker arms)
receive oil through vertical passages from the cylinder block. An oil
pressure sender for the dashboard gauge and an oil pressure switch for
the warning lamp are mounted on the filter head or cylinder block.
The cooling system is a pressurized, water-cooled design using a
belt-driven centrifugal water pump. The system includes a
thermostatically controlled bypass circuit for rapid engine warm-up. A
radiator with an engine-driven fan provides heat rejection.
Coolant Capacity (engine only): 7.5 L (7.9 qt).
Coolant Capacity (with radiator, truck application): 18.0-22.0 L
(19.0-23.3 qt).
Water Pump Type: Centrifugal, belt-driven from crankshaft pulley.
Thermostat Opening Temperature (start): 76°C (169°F).
Thermostat Fully Open Temperature: 90°C (194°F).
Radiator Cap Pressure: 0.9 bar (13 psi).
Fan Type: Suction fan, belt-driven, mounted on water pump pulley.
Recommended Coolant: Ethylene glycol-based, 30-50% concentration.
The cooling system directs coolant from the water pump into the cylinder
block, where it flows around each cylinder bore through vertical
passages. Coolant then enters the cylinder head, flowing across the
combustion deck and exhaust valve seats before exiting through the
thermostat housing at the front of the cylinder head.
The bypass circuit allows coolant to circulate within the engine while
the thermostat remains closed, preventing localized hot spots during
warm-up and reducing warm-up time. A coolant temperature sender for the
dashboard gauge is mounted on the thermostat housing. A second
temperature switch may activate a warning lamp or shutdown system.
12-volt or 24-volt, depending on market and chassis configuration.
Starter Motor: 4.0 kW (12V) or 5.0 kW (24V), pre-engaged type with
integral solenoid. Alternator: 12V, 45-60A (540-720 W) or 24V, 25-35A,
with internal regulator. Glow Plug System (cold climate option): Intake
air heater grid or pencil-type glow plugs in pre-combustion chambers (if
equipped).
Air Intake System: Single dry paper air filter with restriction
indicator. Turbocharged variants include an air-to-air intercooler.
Exhaust System: Cast iron exhaust manifold, single vertical outlet
(truck) or horizontal outlet (industrial).
Engine Control: Mechanical governor with throttle cable. Optional
pneumatic or electric governor for stationary applications.
Engine Monitoring: Coolant temperature gauge, oil pressure gauge,
tachometer (optional), hour meter (industrial applications). Warning
lamps for low oil pressure, high coolant temperature, charge failure.
Fan Drive: Belt-driven, fixed pitch fan. Optional viscous clutch fan for
fuel savings.
Crankcase Ventilation: Open system with breather tube to atmosphere
(early models) or closed system with oil separator returning to intake
(later models).
Dry Weight (complete engine, no fluids, no flywheel): 530 kg (1,168 lb).
Dry Weight (with flywheel and clutch housing): 570 kg (1,257 lb).
Length (front pulley to flywheel housing face): 1,100 mm (43.3 in).
Width (maximum at injection pump): 620 mm (24.4 in).
Width (with exhaust manifold): 680 mm (26.8 in).
Height (oil pan to rocker cover top): 830 mm (32.7 in).
Crankshaft Centerline to Top of Rocker Cover: 360 mm (14.2 in).
Crankshaft Centerline to Bottom of Oil Pan: 260 mm (10.2 in).
Valve Clearance (Cold, Intake and Exhaust): 0.40 mm (0.016 in).
Valve Clearance Inspection Interval: 20,000 km (12,400 miles) or 500
hours.
Engine Oil Change Interval (truck service): 10,000 km (6,200 miles) or
250 hours.
Engine Oil Change Interval (industrial service): 200 hours.
Oil Filter Change Interval: Every oil change.
Fuel Filter Change Interval (secondary): 20,000 km (12,400 miles) or 500
hours.
Fuel Filter Change Interval (primary, water separator): 40,000 km
(24,800 miles).
Coolant Change Interval: 40,000 km (24,800 miles) or 2 years.
Air Filter Service Interval: When restriction indicator shows vacuum
(clean or replace element).
Injector Testing Interval: 40,000 km (24,800 miles) or 1,000 hours.
Injection Pump Timing Check Interval: 40,000 km (24,800 miles).
Fan Belt Tension Check Interval: 10,000 km (6,200 miles) or 10-15 mm
deflection at 10 kg force.
Crankshaft Vibration Damper Inspection Interval: 80,000 km (50,000
miles).
Valve Timing Check Interval: 80,000 km (50,000 miles).
Cylinder Head Bolts (M14, coarse thread): 172 Nm (127 lb-ft).
Cylinder Head Bolts (M10, outer or tappet side): 34 Nm (25 lb-ft).
Main Bearing Cap Bolts: 152 Nm (112 lb-ft).
Connecting Rod Cap Nuts: 103 Nm (76 lb-ft).
Flywheel to Crankshaft Bolts: 186 Nm (137 lb-ft).
Crankshaft Pulley Bolt (front): 245 Nm (181 lb-ft).
Camshaft Drive Gear Bolts: 45 Nm (33 lb-ft).
Injection Pump Drive Gear Bolt: 50 Nm (37 lb-ft).
Intake Manifold Nuts: 25 Nm (18 lb-ft).
Exhaust Manifold Nuts: 30 Nm (22 lb-ft).
Valve Cover Bolts (rocker cover): 10 Nm (89 lb-in).
Rocker Shaft Bracket Bolts: 35 Nm (26 lb-ft).
Rocker Arm Adjusting Locknut: 20 Nm (15 lb-ft).
Oil Pan Bolts: 15 Nm (11 lb-ft).
Oil Drain Plug: 50 Nm (37 lb-ft).
Oil Filter (spin-on): Hand tighten plus 1/2 to 3/4 turn.
Starter Motor Mounting Bolts: 45 Nm (33 lb-ft).
Alternator Pivot Bolt: 40 Nm (30 lb-ft).
Alternator Adjusting Arm Bolt: 25 Nm (18 lb-ft).
Fuel Injectors (hold-down clamp nuts): 25 Nm (18 lb-ft).
Injector Pipe Flare Nuts: 30 Nm (22 lb-ft).
Water Pump Mounting Bolts: 25 Nm (18 lb-ft).
Thermostat Housing Bolts: 15 Nm (11 lb-ft).
Fan Belt Pulley Bolts (water pump): 30 Nm (22 lb-ft).
Viscous Fan Clutch to Pulley Bolts: 25 Nm (18 lb-ft).
Engine Mount Bracket Bolts: 70 Nm (52 lb-ft).
Flywheel Housing to Block Bolts: 60 Nm (44 lb-ft).
Mitsubishi Fuso FM Series Trucks (Medium-Duty): The 6D15 is installed in
FM51, FM55, and FM61 series trucks (GVW 12-18 tons). These vehicles
serve urban delivery, regional freight, and municipal service roles
including dump trucks, cargo vans, and refrigerated box trucks. The FM
series was sold in Asia, Australia, Africa, and South American markets.
Mitsubishi Fuso FK Series Trucks (Light-Medium Duty): The FK series
(FK61, FK62) uses the 6D15 in chassis cab configurations for flatbed and
stake body applications.
Kato Excavators (Construction): Kato Works Co. installed the 6D15 in
HD-series hydraulic excavators in the 15-20 metric ton class, including
the HD-700 and HD-800 models. The engine provides hydraulic pump drive
power for digging, lifting, and swing operations.
Kobelco Excavators (Construction): Kobelco Construction Machinery used
the 6D15 in SK-series excavators (SK150, SK200 early models) before
transitioning to their own engines in later production years.
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