Mitsubishi 4D56U Specifications
| Engine Model: Mitsubishi 4D56U |
| Engine Type: 4-cycle 4-cylinder DOHC 16-valve turbocharged liquid-cooled diesel |
| Total Displacement: 151.2 cu.in (2.47 L) |
| Rated Engine Power: 136-178 Hp (100-131 kW) at 4000 rpm |
| Fuel System Type: Common rail direct injection |
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The Mitsubishi 4D56U is a 2.5-liter, inline-four,
turbocharged diesel engine representing the advanced common-rail evolution of
the venerable 4D56 engine family. Produced from 2005 to 2015, this power unit
departed significantly from its predecessors through the adoption of a dual
overhead camshaft (DOHC) 16-valve cylinder head and second-generation
common-rail direct injection.
Engineered primarily for the fourth generation Mitsubishi L200 (Triton) pickup
and the Pajero Sport SUV, the 4D56U was developed to meet tightening emissions
regulations while delivering improved power density, refinement, and fuel
efficiency over earlier indirect injection variants. The engine utilizes a
variable geometry turbocharger (VGT) with an intercooler to optimize boost
response across the rev range. Available in multiple power outputs calibrated
for manual and automatic transmissions, the 4D56U became a cornerstone
powerplant for Mitsubishi’s global light-commercial and SUV markets during its
production lifecycle.
The Mitsubishi 4D56U is a four-stroke, water-cooled, inline-four diesel engine
with a displacement of 2,477 cc (151.2 cu.in). The bore and stroke dimensions
are 86.0 mm (3.39 in) and 94.0 mm (3.70 in), respectively, yielding a square
configuration that balances low-end torque with high-rpm responsiveness.
The valvetrain employs a dual overhead camshaft (DOHC) design with four valves
per cylinder - two intake and two exhaust - providing enhanced volumetric
efficiency compared to earlier 8-valve iterations. Induction is forced via a
variable geometry turbocharger (VGT) paired with a charge-air cooler
(intercooler) to reduce intake air temperature and increase density.
The fuel system utilizes second-generation common-rail direct injection (CRDi),
operating at pressures up to 1,600 bar (23,206 psi). The compression ratio is
specified between 16.5:1 and 17.0:1, depending on the emission calibration and
market variant.
Standard Output: Delivers 100 kW (136 hp) at 4,000 rpm with a torque rating of
320 Nm (236 lb-ft) at 2,000 rpm, commonly paired with manual transmissions.
High Power (HP) Output: Produces 131 kW (178 hp) at 4,000 rpm and generates a
peak torque of 400 Nm (295 lb-ft) at 2,000 rpm, calibrated for automatic
transmission applications and higher-specification models.
The engine complies with Euro 3 or Euro 4 emissions standards based on market
and production year, utilizing exhaust gas recirculation (EGR) and a diesel
oxidation catalyst. The idle speed is maintained between 650 and 850 rpm.
The cylinder block is constructed from cast iron,
providing the rigidity necessary to withstand the elevated cylinder pressures
associated with common-rail diesel combustion. The block utilizes a deep-skirt
design, with the side walls extending below the crankshaft centerline to enhance
structural stiffness and reduce noise, vibration, and harshness. Cylinder bores
are machined with a plateau honed finish to optimize oil retention and piston
ring sealing.
Press-fit cast iron cylinder liners are incorporated, allowing for overbore
during major overhaul if required. The crankcase accommodates a forged steel
crankshaft supported by five main bearings. To mitigate the inherent
second-order vibrations of an inline-four configuration, the 4D56U incorporates
twin balancer shafts. These shafts are housed within the crankcase, positioned
on either side of the crankshaft centerline, and are driven by a toothed belt
system separate from the main timing belt. This arrangement significantly
improves operational smoothness.
The cylinder head is manufactured from an aluminum
alloy, selected for its superior thermal conductivity and reduced mass compared
to ferrous alternatives. The DOHC arrangement positions two camshafts - one for
the intake valves and one for the exhaust valves - within the head. Each
camshaft acts directly upon hydraulic valve lash adjusters and roller finger
followers, eliminating the need for periodic valve clearance adjustments while
reducing frictional losses.
The four valves per cylinder are arranged in a pent-roof combustion chamber
configuration, optimizing the placement of the centrally located fuel injector
and the glow plug. The intake valves are larger in diameter to maximize airflow,
while the exhaust valves are constructed from heat-resistant steel to withstand
elevated exhaust gas temperatures. The cylinder head gasket is a multi-layer
steel (MLS) design, ensuring a durable seal between the aluminum head and iron
block under the fluctuating thermal and mechanical loads characteristic of
turbocharged diesel operation.
The fuel system is a second-generation common-rail
direct injection system manufactured by DENSO. The supply pump, designated as
the HP3 type, is a high-pressure pump mounted to the engine and driven by the
timing belt. This pump draws fuel from the chassis-mounted tank, passes it
through a water-separating fuel filter, and delivers it to the common rail at
pressures reaching 1,600 bar.
The common rail functions as a high-pressure accumulator, maintaining stable
fuel pressure for all four injectors. The injectors are solenoid-type G2 units,
each featuring a unique QR code. This QR code is scanned during installation and
programmed into the engine control unit (ECU), allowing the ECU to apply precise
individual fuel quantity corrections for each injector to compensate for
manufacturing tolerances.
The ECU manages injection timing, duration, and the number of pilot injections
per cycle based on inputs from the crankshaft position sensor, accelerator pedal
position sensor, and manifold absolute pressure sensor. A fuel temperature
sensor integrated into the supply pump allows the system to adjust injection
parameters to maintain optimal combustion under varying fuel temperatures.
The lubrication system is a full-flow, pressurized
circuit utilizing a trochoid-type oil pump mounted within the timing case and
driven by the crankshaft. The pump draws engine oil from a steel sump through a
strainer screen before directing it through a full-flow spin-on oil filter. An
integrated oil cooler, of the water-to-oil type, is mounted to the oil filter
housing and utilizes engine coolant to maintain stable oil temperature during
sustained high-load operation. The main oil gallery distributes pressurized oil
to the crankshaft main bearings, connecting rod bearings, camshaft bearings, and
the hydraulic valve lash adjusters.
Dedicated oil jets are positioned within the crankcase to direct a continuous
spray of oil to the underside of each piston crown, providing essential cooling
to the piston rings and ring grooves during high thermal operation. The twin
balancer shafts are also integrated into the pressurized lubrication circuit,
receiving oil through dedicated passages. The total engine oil capacity,
including the filter, is approximately 5.5 L (5.8 qt).
The cooling system operates as a pressurized,
thermostatically controlled water circulation circuit. A belt-driven centrifugal
water pump, mounted to the front of the cylinder block, circulates a mixture of
water and ethylene glycol antifreeze through the cylinder block, cylinder head,
turbocharger bearing housing, and the main radiator. The thermostat is a
wax-pellet type positioned on the coolant inlet side of the water pump,
providing rapid warm-up and precise temperature regulation by restricting
coolant flow to the radiator until operating temperature is reached.
The radiator is a cross-flow aluminum construction with plastic end tanks,
optimized for maximum heat exchange efficiency within the constraints of the
vehicle chassis. An electric cooling fan, controlled by the ECU based on coolant
temperature and air conditioning load, provides forced airflow during low-speed
operation or high ambient temperatures. The coolant reservoir is of the
expansion tank type, allowing for coolant expansion and providing a point for
air separation. The total cooling system capacity is approximately 6.3 L (6.7
qt).
| Intake and Exhaust Systems |
Intake System: The intake manifold is constructed from
aluminum and features integrated swirl control valves in many applications.
These valves are actuated by a vacuum-controlled actuator and are designed to
generate swirl motion in the intake air at low engine speeds, improving air-fuel
mixing and combustion stability. The variable geometry turbocharger (VGT)
adjusts its turbine vanes electronically under ECU control, varying the aspect
ratio to provide rapid boost response at low rpm while preventing overspeed at
high rpm. The charge-air cooler is of the air-to-air type, mounted forward of
the radiator.
Exhaust System: The exhaust manifold is constructed from high-grade cast iron
and is designed to maintain heat energy to the turbocharger while withstanding
thermal cycling. The after-treatment system includes a diesel oxidation catalyst
(DOC) mounted close to the engine to achieve rapid light-off. Some Euro 4
variants also incorporate a diesel particulate filter (DPF) as part of the
emissions control strategy, with regeneration managed automatically through
post-injection of fuel.
The engine length, measured from the front accessory
drive pulley to the flywheel housing mating face, is 640 mm (25.2 in). Width
across the cylinder head, intake manifold, and turbocharger assembly is 700 mm
(27.6 in). Height from the bottom of the oil sump to the top of the cylinder
head cover is 750 mm (29.5 in). The dry weight of the engine, inclusive of the
alternator, starter motor, turbocharger, and injection system but without
transmission or fluids, is 220 kg (485 lb).
The engine oil must meet API CI-4 or ACEA B4
specifications with a viscosity grade of 5W-30, 5W-40, or 10W-40 selected
according to ambient temperature. The oil change interval is determined by the
vehicle’s service indicator system, with a maximum interval of 15,000 km (9,321
mi) or 12 months under normal operation. Severe duty applications, including
frequent towing or dusty environments, require a reduced interval of 7,500 km
(4,660 mi).
The oil filter is replaced at each oil change. The fuel filter incorporates a
water separator and requires replacement every 30,000 km (18,641 mi) or as
indicated by the water-in-fuel warning lamp. The air filter element is inspected
at each service and replaced at 45,000 km (27,961 mi) intervals, with more
frequent replacement required in dusty conditions.
The timing belt, tensioner, and idler pulleys must be replaced at 100,000 km
(62,137 mi) to prevent catastrophic engine damage. The coolant requires
replacement every 45,000 km (27,961 mi) or every two years, utilizing a
long-life antifreeze formulation meeting Mitsubishi specifications. Valve
clearance is maintained automatically by hydraulic lash adjusters and requires
no periodic adjustment.
Cylinder Head Bolts, Stage one: 40 Nm (30 lb-ft).
Cylinder Head Bolts, Stage two: 90 Nm (66 lb-ft).
Main Bearing Cap Bolts: Stage one: 40 Nm (30 lb-ft).
Connecting Rod Cap Bolts: Stage one: 30 Nm (22 lb-ft).
Camshaft Bearing Caps: 12 Nm (9 lb-ft).
Flywheel Bolts: Stage one: 50 Nm (37 lb-ft).
Crankshaft Pulley Bolt, Stage one: 200 Nm (148 lb-ft).
Crankshaft Pulley Bolt, Stage two: 45 Nm (33 lb-ft).
Intake Manifold Bolts: 23 Nm (17 lb-ft).
Exhaust Manifold Nuts: 30 Nm (22 lb-ft).
Injector Clamp Bolts: 25 Nm (18 lb-ft).
Oil Filter Housing to Block: 25 Nm (18 lb-ft).
Engine Mounting Brackets: 55 Nm (41 lb-ft).
Timing Belt Tensioner Bolt: 50 Nm (37 lb-ft).
The Mitsubishi 4D56U engine was deployed across
Mitsubishi’s global light-commercial vehicle and SUV lineup during its
production run from 2005 to 2015.
Mitsubishi L200 (Triton)-Fourth Generation: The 4D56U served as the primary
diesel power unit for the fourth generation L200 pickup, marketed as the Triton
in Asia-Pacific and European markets. It was offered in both standard output and
high power calibrations, with availability varying by market and trim level. The
engine was paired with either a five-speed manual transmission or a five-speed
automatic transmission depending on the output variant.
Mitsubishi Pajero Sport: This SUV, based on the L200 chassis platform, utilized
the 4D56U across its model range. The engine was calibrated to provide the
torque characteristics suited for both on-road comfort and off-road capability,
with the high power variant reserved for top-tier specifications.
Mitsubishi Pajero (Fourth Generation): In select markets, particularly those
with emissions regulations favoring the 2.5-liter displacement, the 4D56U was
offered as an entry-level diesel option in the full-size Pajero (Montero) SUV,
providing a balance of fuel economy and adequate power for the heavy chassis.
Mitsubishi Delica D:5: The fourth generation Delica minivan incorporated the
4D56U in certain market applications, where the engine’s compact dimensions and
torque delivery suited the vehicle’s crossover utility configuration.
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