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Mitsubishi 4D56 Specifications
| Engine Model: Mitsubishi 4D56 |
| Engine Type: 4-cycle inline 4-cylinder full-pressure lubrication liquid-cooled diesel |
| Total Displacement: 151.1 cu.in (2.47 L) |
| Rated Engine Power: 75-82 Hp (55-60 kW) at 4200 rpm |
| Fuel System Type: Indirect fuel injection |
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| General Technical Data |
The Mitsubishi 4D56 is a 2.5-liter inline-four, four-stroke, water-cooled diesel engine that has been one of Mitsubishi’s most widely used powerplants since its introduction in the early 1980s. Designed primarily for light commercial vehicles, pickup trucks, and SUVs, it became renowned for its ruggedness, fuel efficiency, and reliability.
The engine belongs to Mitsubishi’s 4D5 family, replacing the earlier 4D55 unit and serving as the foundation for both naturally aspirated and turbocharged derivatives. The standard 4D56 (non-turbo) is characterized by a mechanical indirect fuel injection system and simple design that ensures easy maintenance and longevity, especially in harsh environments.
Its cast-iron block and head construction,
combined with conservative tuning, enable excellent durability and
tolerance for varying fuel qualities. This engine has powered numerous
Mitsubishi models such as the L200, Pajero, and Delica, and has also
been licensed or adapted for other regional manufacturers worldwide.
The 4D56 became a workhorse engine across several decades, appreciated
by fleet operators and private owners alike. Its balance of output and
efficiency made it suitable for utility vehicles requiring dependable
torque rather than high performance. It represents Mitsubishi’s
commitment to robust engineering, serving as a benchmark diesel engine
during its production era. Although later replaced by modern common-rail
variants, the standard 4D56 remains widely used and supported globally.
The Mitsubishi 4D56 engine has a total displacement of 2,476 cc (151.1
cubic inches). This is achieved through a bore of 91.1 mm (3.59 inches)
and a stroke of 95.0 mm (3.74 inches), resulting in a slightly
undersquare configuration that favors torque at lower engine speeds. The
compression ratio is approximately 21.0:1, typical for
indirect-injection diesel engines. The firing order is 1-3-4-2. The
crankshaft rotates clockwise viewed from the front, and the engine
operates on the conventional four-stroke diesel cycle: intake,
compression, power, and exhaust.
The engine block is cast iron with replaceable wet-type cylinder liners,
providing excellent serviceability and structural rigidity. The cylinder
head is also cast iron, featuring two valves per cylinder operated by an
overhead camshaft via rocker arms and adjustable tappets. The camshaft
is belt-driven from the crankshaft through a toothed rubber timing belt
that also drives the water pump and balance shafts. The 4D56 employs
twin counter-rotating balance shafts driven by a separate belt, a design
that significantly reduces secondary vibrations common in inline-four
diesel engines.
Maximum output for the naturally aspirated 4D56 is typically around 55
to 60 kW (75 to 82 horsepower) at 4,200 revolutions per minute, while
peak torque is approximately 142 to 148 Nm (105 to 109 lb-ft) at 2,500
rpm. The engine redline is around 4,500 rpm, with a governed maximum
speed near 4,800 rpm. Idle speed is set at approximately 750 ± 50 rpm.
The engine’s design emphasizes low-end torque and drivability rather
than high power, making it ideal for off-road and load-carrying
applications.
The pistons are made of aluminum alloy with steel inserts for the top
ring grooves to resist wear and high thermal load. Each piston has three
rings - two compression rings and one oil control ring. Connecting rods
are forged steel, and the crankshaft is a forged steel five-bearing
design with induction-hardened journals. The main bearings and
connecting rod bearings are replaceable shell-type, and thrust washers
control end play. Valve clearance is adjusted manually using a
screw-and-locknut arrangement.
| Fuel System |
The 4D56 uses a mechanically controlled indirect injection fuel system. Fuel is drawn from the tank by a mechanical lift pump and delivered to an inline injection pump (typically a Bosch VE-type or licensed equivalent). The pump meters and pressurizes the diesel fuel, distributing it to four injectors via high-pressure steel lines.
Injection pressure ranges from approximately 140 to 160 bar (2,030 to
2,320 psi). The injectors are pintle-type, designed to atomize fuel into
the pre-combustion chambers located in the cylinder head. Combustion
then propagates into the main chamber, producing smooth and efficient
burning.
The fuel filter assembly includes a water separator and hand-priming
pump to remove air from the system. Regular fuel filter replacement is
essential to maintain proper injection performance. Recommended fuel is
automotive diesel with a cetane number of 50 or higher. The system is
entirely mechanical, requiring no electronic controls, which contributes
to reliability in remote or low-maintenance environments.
| Lubrication System |
The lubrication system is a full-pressure, wet-sump type. An internal
gear-type oil pump, driven directly by the crankshaft, draws oil through
a pickup strainer and delivers it under pressure to the main oil
gallery. From there, oil is distributed to the crankshaft bearings,
connecting rod journals, camshaft bearings, and valve train components.
The piston undersides are cooled by oil jets to reduce thermal stress. A
full-flow spin-on type oil filter is located on the side of the block,
easily accessible for maintenance.
Normal oil pressure is approximately 350 to 500 kPa (50 to 72 psi) at
3,000 rpm, and around 100 kPa (15 psi) at idle. The total oil capacity,
including the filter, is about 5.5 liters (5.8 US quarts, 4.8 Imperial
quarts). Recommended oil viscosity is SAE 15W-40 or 10W-30 meeting API
CF or higher specifications.
Oil and filter changes are recommended every 5,000 to 10,000 km (3,000 to 6,000 miles) depending on service severity. The crankcase ventilation system uses a closed-type positive crankcase ventilation (PCV) setup that routes blow-by gases through a breather to the intake manifold.
| Cooling System |
The 4D56 engine employs a liquid cooling system with forced circulation.
The centrifugal water pump, driven by the timing belt, circulates
coolant through the block, head, radiator, and heater core. The
thermostat begins to open at approximately 82 C (180°F) and is fully
open near 95°C (203°F). A cross-flow brass or aluminum radiator is used
depending on vehicle application, and airflow is provided by a
belt-driven or viscous clutch fan. The system operates under pressure,
typically around 88 kPa (13 psi), to raise the boiling point of the
coolant.
Total coolant capacity is about 8.0 liters (8.5 US quarts, 7.0 Imperial
quarts). Recommended coolant is a 50/50 mixture of ethylene glycol-based
antifreeze and demineralized water, providing protection down to –35°C
(–31°F). Coolant should be replaced every 40,000 km (25,000 miles) or
every two years. The cooling system incorporates a temperature sender
for dashboard indication and an additional sensor for the glow plug
control system.
| Intake and Exhaust Systems |
The intake system uses a cast aluminum manifold optimized for mid-range torque. Air passes through a dry paper air filter element, which should be replaced every 20,000 km (12,000 miles). The exhaust manifold is cast iron, designed for durability under high thermal stress.
Exhaust gas recirculation (EGR) was not fitted on early versions but
became standard on later 4D56 engines to meet tightening emission
standards. The exhaust system incorporates a simple muffler and, in some
markets, an oxidation catalyst for smoke reduction.
Glow plug pre-heating assists cold starts. Four glow plugs, one per
cylinder, are energized by a timer relay during cold conditions to
preheat the pre-combustion chambers. Typical glow plug voltage is 11
volts. The preheat duration varies automatically with ambient
temperature.
| Electrical System |
The electrical system includes a 12-volt alternator rated around 60–80 amperes, depending on model year. The starter motor is a 2.0-kilowatt reduction-gear type for reliable cranking in low temperatures. The battery capacity is typically 70–90 ampere-hours. Engine ground connections must be secure to ensure proper starting and charging performance.
| Valve Timing and Drive Mechanism |
The overhead camshaft is driven by a toothed timing belt from the crankshaft. The same belt also drives the balance shafts and water pump via an auxiliary belt arrangement. The timing belt should be replaced every 100,000 km (60,000 miles) or sooner under severe conditions.
Valve clearance is adjusted manually with the engine cold: intake 0.25 mm (0.010 inch), exhaust 0.35 mm (0.014 inch). Incorrect valve clearance can cause hard starting, poor idle, or excessive noise. Proper tensioning of the balance shaft belt is critical to minimize vibration and ensure smooth operation.
| Dimensions and Weight |
The overall dimensions of the 4D56 engine are approximately 720 mm (28.3 inches) in length, 600 mm (23.6 inches) in width, and 700 mm (27.6 inches) in height. The dry weight is about 185 kg (408 lbs), reflecting its robust cast-iron construction. The engine uses three-point rubber mounts to isolate vibration from the chassis. Depending on the vehicle installation, the sump configuration may differ between front- and rear-wheel-drive applications.
| Maintenance Data |
Engine oil and filter should be replaced at intervals not exceeding 10,000 km (6,000 miles). Fuel filters are replaced every 20,000 km (12,000 miles), and air filters every 20,000 km (12,000 miles) or sooner in dusty environments. Valve clearances should be checked and adjusted every 30,000 km (18,000 miles).
Timing and balance shaft belts must be renewed at 100,000 km (60,000
miles) along with the water pump if necessary. Cooling system
inspection, including hoses and radiator condition, is recommended every
20,000 km (12,000 miles).
Standard compression pressure is approximately 3,000 kPa (435 psi) at
cranking speed, with a minimum allowable limit of 2,550 kPa (370 psi).
The difference between cylinders should not exceed 490 kPa (70 psi).
Engine idle speed is 750 ± 50 rpm. The valve clearance settings, as
noted, are 0.25 mm (0.010 in) for intake and 0.35 mm (0.014 in) for
exhaust when cold.
| Tightening Torques |
Cylinder head bolts: tighten in sequence in three stages – first stage
39 Nm (29 lb-ft), second stage 78 Nm (58 lb-ft), then final angle
tightening 90 degrees.
Main bearing cap bolts: 83 Nm (61 lb-ft).
Connecting rod bolts: 43 Nm (32 lb-ft) plus 90 degrees.
Camshaft bearing cap bolts: 13 Nm (10 lb-ft).
Flywheel bolts: 88 Nm (65 lb-ft) plus 90 degrees.
Crankshaft pulley bolt: 180 Nm (133 lb-ft).
Oil pump cover bolts: 9 Nm (7 lb-ft).
Intake manifold bolts: 25 Nm (18 lb-ft).
Exhaust manifold nuts: 35 Nm (26 lb-ft).
Rocker cover bolts: 9 Nm (7 lb-ft).
Glow plugs: 13 Nm (10 lb-ft).
Oil drain plug: 40 Nm (30 lb-ft).
| Vehicle Applications |
The Mitsubishi 4D56 engine has been used extensively across a range of
vehicles since its introduction.
Notable applications include:
– Mitsubishi L200 / Triton pickup (1986–2005)
– Mitsubishi Pajero / Montero (1983–1999, base models)
– Mitsubishi Delica and L300 vans (1984–2007)
– Mitsubishi Strada (various regional versions)
– Hyundai Galloper and early Kia models (under license)
– Certain JMC and Foton trucks in Asia (adapted under agreement)
The engine’s robust and simple design allowed widespread use in both
civilian and military applications. In many markets, the 4D56 powered
utility vehicles and minibuses used for transport in remote regions. Its
reputation for reliability, combined with mechanical simplicity, has
made it one of Mitsubishi’s most successful diesel engines.
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