Mitsubishi 6D24 Specifications
| Engine Model: Mitsubishi 6D24 |
| Engine Type: 4-cycle inline 6-cylinder liquid-cooled diesel |
| Total Displacement: 729 cu.in (11.95 L) |
| Rated Engine Power: 200 to 350 Hp (149-261 kW) at 2200 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi 6D24 is a 12-liter, heavy-duty
inline 6-cylinder diesel engine widely used in Fuso Super Great trucks,
large buses, and industrial machinery such as Kobelco and Kato
excavators. This engine belongs to Mitsubishi’s D-series, renowned for
robust cast iron construction, direct injection combustion, and high
reliability under sustained heavy loads.
The Mitsubishi 6D24 is produced in naturally aspirated, turbocharged
(6D24-T), and turbocharged with intercooler (6D24-TC and 6D24-TL)
configurations. A piston cooling system using oil jets directed at the
underside of each piston crown reduces thermal stress during continuous
operation. The engine also powers marine vessels and generator sets,
where its 180 kVA output capacity supports standby and prime power
applications.
The Mitsubishi 6D24 is a four-stroke, water-cooled, inline 6-cylinder
diesel engine. The cylinder arrangement is vertical and in-line,
designed for longitudinal mounting in truck frames, bus chassis, or
heavy machinery. The engine block and cylinder head are constructed from
high-strength cast iron.
The valvetrain is an overhead valve (OHV) design with pushrods and
rocker arms, actuated by a camshaft located in the cylinder block. Each
cylinder features two valves - one intake and one exhaust. This
configuration provides durability and ease of service in heavy-duty
applications.
Displacement is 11,945 cc (12.0 L / 729 cu.in), achieved through a bore
of 130.0 mm (5.12 in) and a stroke of 150.0 mm (5.91 in). The
undersquare design (stroke longer than bore) promotes high torque output
at lower engine speeds, critical for truck and excavator applications.
The compression ratio varies by aspiration: 19.5:1 for the naturally
aspirated version, 16.5:1 for the 6D24-T (turbocharged), and 17.5:1 for
the 6D24-TC/TL (turbocharged with intercooler). The combustion system is
direct injection.
The firing order is 1-5-3-6-2-4, a standard inline six sequence
providing perfect primary and secondary balance. Power output ranges
from 200 to 350 hp (149 to 261 kW) depending on variant and application.
The 6D24-TC in industrial configuration produces up to 319 hp (238 kW)
at 2,200 rpm. For generator drive applications at 1,800 rpm, the 6D24-T
produces 280 hp (209 kW) standby power, while the 6D24-TC produces 298
hp (222 kW) standby power. Maximum torque is 1,050 Nm (777 lb-ft) at
1,500 rpm for the 6D24-T, and 1,175 Nm (870 lb-ft) at 1,500 rpm for the
6D24-TC.
The cylinder block is a cast iron, closed-deck design with deep skirt
reinforcements. This construction provides exceptional torsional
rigidity under the high cylinder pressures generated by turbocharged
operation. The block features a 7-main-bearing configuration for the
crankshaft. The crankshaft is forged from high-carbon steel and
induction-hardened.
Connecting rods are forged steel with a precision-finished big end bore.
Pistons are aluminum alloy with steel ring carriers in the top ring
groove for durability under high thermal loads. Each piston carries
three rings: two compression rings and one oil-control ring. An oil jet
is fitted under the main oil gallery for each cylinder, spraying engine
oil onto the inside surfaces of the pistons to aid cooling. In the
6D24-T, TC, and TL variants, each piston has a cooling cavity; oil
sprayed from the oil jets enters these cavities for additional cooling.
Replaceable wet-type cylinder liners are used, allowing in-frame
rebuilding.
The cylinder head is a single cast iron unit spanning all six cylinders.
The combustion chamber is of the direct injection type, with a
re-entrant bowl machined into the piston crown. Valves are arranged in a
straight line along the cylinder head.
The valve train includes adjustable rocker arms with screw-type
adjusters and locking nuts, allowing precise valve clearance setting.
Valve seats are induction-hardened or fitted with replaceable hardened
inserts. Valve guides are replaceable. The cylinder head gasket is a
multi-layer steel design capable of withstanding cylinder pressures
generated by turbocharged operation.
The fuel system is a mechanical direct injection system. An in-line
injection pump (manufactured by Zexel) is mounted to the engine timing
case and driven by a gear from the camshaft. The pump generates
high-pressure fuel pulses and distributes them to each cylinder in the
firing order (1-5-3-6-2-4).
Fuel is delivered from the pump to the injectors through steel
high-pressure lines. The injectors are of the multi-hole nozzle type,
atomizing fuel directly into the combustion bowl in the piston crown. A
mechanical governor is integral to the injection pump, maintaining
engine speed from no-load to full-load conditions.
The lubrication system is a full-pressure, gear-type pump design. The
oil pump is driven by the crankshaft gear train. The system includes a
full-flow spin-on oil filter and a centrifugal bypass filter on some
variants. A water-cooled oil cooler is integrated into the oil filter
base, maintaining stable oil temperature under sustained heavy loads.
Oil pressure delivers to the crankshaft main bearings, connecting rod
bearings, and camshaft bearings.
A separate gallery directs oil upward through the cylinder block to the
rocker shaft assembly. The oil jets for piston cooling are supplied from
the main oil gallery. Part of the engine oil is directed through an oil
pipe from the crankcase to the turbocharger bearing housing for
lubrication; it returns through an oil outlet at the bottom of the
bearing housing back to the crankcase. Total oil capacity is 27.0 liters
(28.5 US qt), depending on the oil pan and application.
The cooling system is a thermostatically controlled, pressurized liquid
cooling system with a belt-driven centrifugal water pump. Coolant is
circulated through the cylinder block, cylinder head, and oil cooler
before returning to the radiator.
The wet cylinder liners allow direct coolant contact for efficient heat
transfer. A wax-pellet thermostat regulates coolant flow. A fan draws
air through the radiator core. The radiator pressure cap is rated for 70
to 100 kPa (10 to 15 psi). The cooling system capacity depends on the
radiator size in each vehicle or machine.
| Intake and Exhaust Systems |
Intake System: The intake system consists of a dry-type replaceable
paper air filter, a turbocharger (on T, TC, TL variants), a charge air
cooler (on TC and TL variants), and a cast iron intake manifold. The
charge air cooler reduces intake air temperature after turbocharger
compression.
Exhaust System: A cast iron exhaust manifold collects gases from all six
cylinders and feeds the turbocharger turbine inlet on turbocharged
variants. The system operates at elevated temperatures.
Turbocharger System: The turbocharger is an oil-lubricated unit. A
piston ring is installed on the outside of each turbocharger bearing,
serving as an oil seal. The wastegate controls maximum boost pressure.
Electrical System: The engine is equipped with a 24-volt electrical
system for commercial vehicle and industrial applications. The starter
motor is a gear-reduction type. The alternator is a belt-driven unit
with charging capacity appropriate to the application.
Length, measured from the front pulley to the flywheel housing mounting
face, is 1,400 mm (55.1 in). Width, measured across the cylinder head
and intake manifold, is 800 mm (31.5 in). Height from the bottom of the
oil pan to the top of the valve cover is 1,100 mm (43.3 in).
Dry weight of the complete engine assembly ranges from 950 to 1,200 kg
(2,095 to 2,646 lb), varying by variant and installed equipment. The
turbocharged version weighs 961 kg (2,119 lb), while the turbocharged
and intercooled version weighs 960 kg (2,117 lb).
Routine maintenance is critical for the longevity of the heavy-duty
diesel 6D24. The mechanical fuel system requires periodic injection
timing checks and injector testing. Oil Capacity: With oil filter
change, the crankcase capacity is 27.0 liters (28.5 US qt), depending on
the oil pan. Oil Filters: Spin-on full-flow filter. Replacement interval
coincides with each oil change. Oil Change Interval: Under normal
heavy-duty service, the engine oil and filter should be changed every
250 to 500 hours or every six months, whichever comes first.
Fuel Filters: Primary and secondary spin-on filters with water
separator. Replacement interval is 500 operating hours or annually. Air
Filter Service: The dry-type air filter element should be inspected
every 250 operating hours and replaced when the restriction indicator
shows red. Engine Coolant: A 50/50 mixture of ethylene glycol antifreeze
and distilled water is required. Coolant Change Interval: 2,000
operating hours or two years, whichever comes first.
Valve Clearance (Cold): Adjust with the engine at ambient temperature.
Intake valve clearance is 0.40 mm (0.016 in). Exhaust valve clearance is
0.60 mm (0.024 in). Valve Lash Adjustment Interval: 1,000 operating
hours. Injection Pump Timing: Static timing is set by shim adjustment
between the pump and timing case. Injector Opening Pressure:
Approximately 200 to 220 bar (2,900 to 3,190 psi).
Cylinder Head Bolts: 175 Nm (129 lb-ft).
Main Bearing Bolts: 115 Nm (85 lb-ft).
Connecting Rod Bolts: 115 Nm (85 lb-ft).
Flywheel Housing to Cylinder Block Bolts: 80 Nm (59 lb-ft).
Flywheel to Crankshaft Bolts: 150 Nm (111 lb-ft).
Intake Manifold Nuts: 35 Nm (26 lb-ft).
Exhaust Manifold Nuts: 45 Nm (33 lb-ft).
Turbocharger Mounting Nuts: 55 Nm (41 lb-ft).
Injection Pump Mounting Nuts: 40 Nm (30 lb-ft).
Injector Clamp Bolts: 35 Nm (26 lb-ft).
High-Pressure Fuel Line Nuts: 30 Nm (22 lb-ft).
Valve Cover Bolts: 15 Nm (11 lb-ft).
Oil Pan Bolts: 25 Nm (18 lb-ft).
Oil Filter (Spin-On): 20 Nm (15 lb-ft) or 3/4 turn after gasket contact.
Water Pump Mounting Bolts: 30 Nm (22 lb-ft).
Thermostat Housing Bolts: 20 Nm (15 lb-ft).
Crankshaft Pulley Bolt: 350 Nm (258 lb-ft).
Starter Motor Mounting Bolts: 80 Nm (59 lb-ft).
The Mitsubishi 6D24 engine was utilized across a wide range of
heavy-duty commercial vehicles, construction machinery, industrial
equipment, and power generation systems.
Truck Applications:
Mitsubishi Fuso Super Great (various model years).
Mitsubishi Fuso The Great (model code 417, 1995-1996).
Excavator Applications:
Kobelco SK480-6 excavator.
Kato excavators.
Hitachi excavators (rebranded configurations).
HD1430-3 excavator.
Industrial Machinery Applications:
Kobelco construction equipment.
Kato Industries heavy machinery.
Forklifts.
Generator Applications:
Prime and standby generator sets rated at 180 kVA.
Marine auxiliary generator sets.
Marine Applications:
Commercial vessel auxiliary power.
Small workboat propulsion.
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