Mitsubishi 4D34T Specifications
| Engine Model: Mitsubishi 4D34T |
| Engine Type: 4-cycle inline 4-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 238.5 cu.in (3.9 L) |
| Rated Engine Power: 135-150 Hp (100-112 kW) at 2900 rpm |
| Fuel System Type: Direct fuel injection |
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The Mitsubishi 4D34T is a turbocharged variant
of the widely used 4D34 four-cylinder diesel engine that powered
numerous Mitsubishi Fuso Canter light- and medium-duty trucks as well as
industrial and auxiliary equipment. Designed for commercial environments
requiring improved torque, stronger mid-range power, and long-term
reliability, the 4D34T builds on the proven cast-iron foundation of the
naturally aspirated 4D34 while adding forced induction to improve
drivability and fuel efficiency.
Engineers emphasized durability, simple mechanical serviceability, and
resistance to thermal stress, allowing the engine to operate for
extended hours under full load. Its gear-driven timing system,
mechanical injection pump, and robust internal architecture give the
4D34T a long service life in markets where fuel quality, climate, and
road conditions vary widely.
The 4D34T became especially prominent in export markets and industrial
applications because of its torque-rich output at low RPM. Operators
value the engine for its strong pulling capability, cold-start
reliability, and compatibility with PTO (power take-off) systems,
hydraulic pumps, and construction attachments. Many engines remain in
active duty decades after production, reflecting Mitsubishi’s emphasis
on longevity and conservative engineering.
The Mitsubishi 4D34T is a four-stroke, water-cooled, inline
four-cylinder diesel engine equipped with a turbocharger and, in some
variants, an intercooler. Total displacement is 3,908 cc (238.5 cubic
inches). The bore is 104 mm (4.09 inches), and the stroke is 115 mm
(4.53 inches), creating a long-stroke configuration optimized for high
torque and fuel efficiency. Compression ratio varies slightly depending
on turbo calibration, generally ranging between 17.0:1 and 18.0:1.
Power output for the 4D34T varies by market
and model year:
- Turbocharged non-intercooled versions produce 135-150 Hp (100-112 kW)
at 2,800-3,000 rpm.
- Turbocharged intercooled versions (4D34T4) may reach up to 155-165 Hp
(116-123 kW) at similar speeds.
Peak torque also varies:
- Non-intercooled: 350-380 Nm (258-280 lb-ft) around 1,600-1,800 rpm.
- Intercooled: 400-430 Nm (295-317 lb-ft) in the same range.
Idle speed is generally 700-750 rpm. Maximum governed speed is
3,000-3,200 rpm for truck applications, with industrial versions
governed lower for continuous duty. The firing order is 1-3-4-2. Redline
is usually set around 3,600-3,800 rpm.
The crankshaft is a forged-steel, fully counterweighted unit supported
by five main bearings. Pistons are cast aluminum alloy, reinforced for
turbocharged operation, with precision-shaped combustion bowls. The ring
pack uses two compression rings and one oil-control ring. Connecting
rods are forged steel and sized to manage high combustion loads. The
camshaft is housed in the block and is gear-driven, eliminating
timing-belt maintenance requirements.
The cylinder block is cast iron with heavy ribbing for rigidity. Coolant
passages are arranged to maintain uniform cylinder temperatures,
reducing thermal distortion during high load operation. The crankcase
includes high-strength bearing saddles to support the rotating assembly.
Oil galleries distribute pressurized oil to main bearings, rod bearings,
camshaft bearings, rocker assemblies, and turbocharger bearings. The
block supports various auxiliary components including vacuum pumps,
hydraulic pumps, air compressors, and alternator mounts.000000000000000000000
The cylinder head is cast iron to maintain stability under turbocharged
thermal conditions. Depending on production year, the head may feature
direct-injection combustion chambers or pre-combustion chambers in
earlier variants.
Most 4D34T engines use DI (direct injection) with multi-hole injectors
matched to piston bowl design. The valvetrain includes overhead valves
actuated by pushrods and rocker arms from the gear-driven camshaft.
Valve seats are hardened.
Cold valve clearances are:
- Intake: 0.25-0.30 mm (0.010-0.012 in)
- Exhaust: 0.35-0.40 mm (0.014-0.016 in)
The fuel delivery system is fully mechanical and designed for
durability. A mechanical lift pump draws diesel from the tank and feeds
it through a primary sediment bowl or water separator and then through a
secondary fine paper filter.
Fuel enters a high-pressure mechanical injection pump - either inline or
rotary - depending on version. The pump meters fuel quantity and
controls injection timing. Injection pressures range from 250-350 bar.
Injectors are multi-hole mechanical units designed for precise
atomization into the piston’s combustion bowl. Fuel system reliability
is high, and the engine tolerates moderate contamination, though
performance improves with clean diesel fuel of at least 45 cetane.
Fuel system maintenance:
- Replace filters every 10,000-15,000 km (6,200-9,300 mi).
- Service injectors every 40,000-60,000 km (25,000-37,000 mi).
- Drain water separator regularly.
- Check injection timing at major service intervals.
The 4D34T uses a full-pressure wet-sump lubrication system. A
gear-driven oil pump draws oil from the sump through a mesh pickup
screen and delivers it through a full-flow spin-on filter. Pressurized
lubrication is provided to crankshaft main bearings, connecting rods,
camshaft bearings, rocker arms, and the turbocharger. Some versions
include piston-cooling oil jets for heat control under heavy load.
Oil capacity is 8-10 liters (8.4-10.5 US quarts). Normal operating
pressure ranges from 300-450 kPa (44-65 psi) at speed and 100-150 kPa
(15-22 psi) at idle. Recommended oil viscosity is SAE 15W-40 or 20W-50
heavy-duty diesel oil meeting API CF or higher.
Oil change intervals:
- Automotive use: every 5,000-7,500 km (3,000-4,600 mi).
- Industrial use: 200-250 operating hours.
The cooling system is a forced-circulation liquid cooling system. A
belt-driven centrifugal water pump circulates coolant through the block,
head, radiator, and heater core. A thermostat begins opening at about
82°C (180°F) and is fully open near 95°C (203°F).
Cooling system capacity is generally 9-12 liters (9.5-12.7 US quarts).
System pressure is maintained by a radiator cap rated around 70-90 kPa
(10-13 psi). A 50/50 mix of ethylene glycol and distilled water is
recommended.
Turbocharged versions generate more heat
than naturally aspirated engines, so many 4D34T models include:
- An engine oil cooler
- A water-cooled turbocharger (some variants)
- Larger or multi-row radiators
- Intercoolers for intake-air cooling on T4 versions
| Intake and Exhaust Systems |
The intake system varies with application. Automotive versions use
dry-element air filters, while industrial installations may use oil-bath
or cyclone pre-cleaners. Turbocharged intake airflow is routed through
the turbo compressor housing. Intercooled models pass compressed air
through an air-to-air intercooler to lower temperature and increase
density.
Exhaust manifolds are cast iron for durability under continuous thermal
cycling. Turbochargers mount directly to the exhaust manifold.
Industrial exhaust systems may include spark arrestors, heavy mufflers,
or vertical stacks.
Electrical systems may be 12-volt or 24-volt depending on application.
Alternator output ranges from 40-70 A. Starter motors are rated from
2.0-3.0 kW. Glow plugs assist cold starting. Wiring looms are reinforced
for vibration resistance. Some later 4D34T variants incorporate
electronic fuel-pump controls, sensors, and idle-stabilization systems.
Depending on installation, the 4D34T may
support:
- Hydraulic pump drives
- Vacuum pumps for brake boosters
- Air-conditioning compressors
- Power steering pumps
- PTO attachments
- Marine heat-exchanger cooling systems
- Length: 780-820 mm (30.7-32.3 in)
- Width: 650-700 mm (25.6-27.6 in)
- Height: 820-860 mm (32.3-33.9 in)
Dry weight generally ranges from 270-330 kg (595-727 lb) depending on
turbo and accessory configuration.
- Engine oil and filter: every 5,000-7,500 km
- Fuel filters: 10,000-15,000 km
- Air filter: 8,000-12,000 km
- Coolant: every 30,000 km or 2 years
- Valve lash: every 15,000-20,000 km
- Injectors: every 40,000-60,000 km
- Compression test: every 100,000 km
- Drive-belt inspection: every service interval
- Cylinder head bolts: 120-140 Nm
- Main bearing caps: 120-140 Nm
- Connecting-rod bolts: 55-65 Nm
- Flywheel bolts: 110-130 Nm
- Crankshaft pulley bolt: 180-210 Nm
- Oil drain plug: 35-45 Nm
- Injector hold-downs: 20-25 Nm
- Glow plugs: 10-15 Nm
The Mitsubishi 4D34T is widely used in:
- Mitsubishi Fuso Canter trucks
- Light and medium-duty commercial trucks
- Small buses and shuttle vehicles
- Construction equipment
- Hydraulic power units
- Agricultural machinery
- Generator sets
- Marine auxiliary drives
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