Mitsubishi 4D31T Specifications
| Engine Model: Mitsubishi 4D31T |
| Engine Type: 4-cycle inline 4-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 201.3 cu.in (3.29 L) |
| Rated Engine Power: 82-130 Hp (62-96 kW) at 2100-3500 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi 4D31T is a 3.3-liter,
four-cylinder turbocharged diesel engine from the Mitsubishi 4D3 series.
Developed as the forced-induction variant of the naturally aspirated
4D31, this power unit gained popularity in the late 1980s and early
1990s as a reliable power source for medium-duty trucks like the
Mitsubishi Fuso Canter (FE series) and various industrial machines,
including Kobelco and Kato excavators. The Mitsubishi 4D31T utilizes a
direct injection combustion system and a lower compression ratio than
its naturally aspirated counterpart to accommodate the increased
cylinder pressures generated by the turbocharger.
The Mitsubishi 4D31T engine is a four-stroke, compression-ignition
diesel unit featuring an inline four-cylinder layout. The bore-to-stroke
ratio is slightly undersquare, a design that promotes torque production
at lower engine speeds, which is advantageous for truck and construction
machinery applications where pulling power and lugging capability are
required. The direct injection combustion system provides improved
thermal efficiency and specific fuel consumption compared to indirect
injection designs.
Engine Type: Inline 4-cylinder, 4-stroke, water-cooled, turbocharged
diesel
Displacement: 3.3 L; 3298 cc (201.3 cu.in)
Bore: 100.0 mm (3.94 in)
Stroke: 105.0 mm (4.13 in)
Firing Order: 1-3-4-2
Compression Ratio: 16.0:1
Combustion System: Direct injection
Aspiration: Turbocharged
Rated Engine Speed: 2100-3500 rpm (application dependent)
Maximum Power (Fuso Canter): 96.0 kW (130.0 hp) at 3500 rpm (gross)
Maximum Power (Kato HD400VII): 62 kW (82 hp) at 2100 rpm
Maximum Power (Alternative Rating): 65.0 kW (87.0 hp) at 2100 rpm
Maximum Torque (Kato HD400VII): 298.3 Nm (220.0 lb-ft) at 1700 rpm
Maximum Torque (Fuso Canter): 294.0 Nm (217.0 lb-ft) at 2000 rpm
Maximum Torque (Alternative Rating): 300.0 Nm (221.0 lb-ft) at 2000-2200
rpm
Compression Pressure (Standard): 2.75 MPa (398 psi) at cranking speed
Compression Pressure (Minimum): 1.96 MPa (284 psi) at cranking speed
Idle Speed: 650-750 rpm (application dependent)
The cylinder block is constructed from cast iron, providing the
structural rigidity required to withstand the elevated cylinder
pressures generated by turbocharged diesel operation. The block is of a
heavy-duty design, featuring thick bulkheads and reinforced main bearing
webs.
The crankshaft is supported by five main bearings to distribute
combustion loads across multiple bearing surfaces. The cylinder bores
are machined directly into the cast iron block.
The cylinder head is manufactured from cast iron and utilizes an
overhead valve (OHV) configuration with a single camshaft located in the
cylinder block. The valvetrain operates the valves through pushrods and
rocker arms. This configuration provides two valves per cylinder - one
intake and one exhaust. The valve arrangement uses a cross-flow design
with intake and exhaust ports on opposite sides of the cylinder head.
Valve Arrangement: 2 valves per cylinder (1 intake, 1 exhaust), OHV
Camshaft Drive: Gear-driven from the crankshaft
Valve Lifters: Mechanical flat tappets
Valve Clearance (Cold): Intake: 0.40 mm (0.016 in); Exhaust: 0.40 mm
(0.016 in)
Valve Adjustment Procedure: With piston at top dead center of
compression stroke for each cylinder, adjust rocker arm screw to
specified clearance while lock nut is loosened, then tighten lock nut to
secure adjustment.
The fuel system is a direct injection design utilizing an in-line
mechanical injection pump. This mechanical system provides reliable
serviceability, as it is free from electronic controls. The injection
pump generates high pressure for the injectors, which deliver fuel
directly into the combustion chamber recess in the piston crown. A
mechanical centrifugal governor maintains engine speed under varying
loads, a critical feature for both vehicle and industrial applications.
Injection Pump Type: Mechanical in-line
Governor Type: Mechanical centrifugal governor
Injector Type: Mechanical multi-hole nozzle
Injection Timing: 13°-15° BTDC
Injection Order: 1-3-4-2
Fuel Feed Pump: Mechanical diaphragm type
Fuel Filter: Spin-on type with replaceable element
Fuel Type: Diesel fuel
The lubrication system is a full-pressure, wet-sump design. A gear-type
oil pump, driven directly from the crankshaft, circulates engine oil
through a full-flow spin-on oil filter. The turbocharger receives
pressurized oil through a dedicated supply line, with oil draining back
to the crankcase via a gravity-fed return line. A pressure relief valve
maintains system pressure within operating limits. The oil pan capacity
accommodates the increased oil volume required by the turbocharger
lubrication circuit.
Oil Capacity (with filter): 7.5-8.5 L (7.9-9.0 qt)
Recommended Oil Grade: SAE 15W-40 meeting API CF, CF-4, or CH-4
Oil Pressure (Rated Speed): 300-400 kPa (3.0-4.0 bar; 44-58 psi)
Oil Pressure (Hot Idle): 70 kPa minimum (0.7 bar; 10 psi)
Oil Filter Type: Spin-on, full-flow
The cooling system is a pressurized water-cooled design utilizing a
belt-driven centrifugal water pump. A wax-pellet thermostat regulates
coolant temperature by controlling flow between the engine and the
radiator. The cooling system is designed to handle the increased thermal
load generated by the turbocharger, with provisions for proper coolant
circulation around the exhaust valve area and cylinder head. A
mechanically driven engine cooling fan provides forced airflow through
the radiator.
Coolant Capacity (engine only): 5.5-6.5 L (5.8-6.9 qt)
Coolant Capacity (engine with radiator): 10.0-12.0 L (10.6-12.7 qt)
Thermostat Opening Temperature: 76-82 °C (169-180 °F)
Thermostat Full Open Temperature: 90-95 °C (194-203 °F)
System Pressure Cap Rating: 70-100 kPa (0.7-1.0 bar; 10-15 psi)
Water Pump Type: Centrifugal, belt-driven
| Intake and Exhaust Systems |
Intake System: Intake air is drawn through a dry-type dual-element air
cleaner before entering the turbocharger compressor inlet. Compressed
air flows through an intake manifold to the cylinder head ports.
Exhaust System: A cast iron exhaust manifold collects exhaust gases from
the cylinder head and directs them to the turbocharger turbine inlet.
Turbocharger: A single turbocharger is mounted to the exhaust manifold,
utilizing exhaust gas energy to drive a compressor wheel that
pressurizes intake air.
Electrical System: 12-volt or 24-volt system depending on the
application. The alternator output varies by vehicle specification.
Starting Aid: Glow plug system for cold weather starting assistance.
The cast iron construction of the 4D31T results in substantial mass
relative to its displacement, reflecting its heavy-duty design for
commercial and industrial applications.
Overall Length: 850 mm (33.5 in)
Overall Width: 650 mm (25.6 in)
Overall Height: 800 mm (31.5 in)
Dry Weight (without fluids): 265 kg (584 lb)
Valve Clearance (Cold): 0.40 mm (0.016 in) for both intake and exhaust.
Valve Adjustment Interval: Inspect and adjust every 1000 operating
hours.
Engine Oil and Filter Replacement Interval: 250 hours under normal
conditions.
Engine Oil and Filter Replacement Interval: 150 hours under severe or
dusty conditions.
Fuel Filter Replacement Interval: 500 operating hours.
Air Filter Elements: Replace element based on restriction indicator.
Coolant Replacement Interval: 2000 operating hours or 2 years.
Injection Timing: 13°-15° BTDC; confirm with engine data plate.
Injector Service: Test and calibrate every 1500-2000 operating hours.
Compression Pressure Test: Standard 2.75 MPa (398 psi).
Compression Pressure Test: Minimum 1.96 MPa (284 psi).
Cylinder Head Bolts (Step 1): 88.0 Nm (65.0 lb-ft)
Cylinder Head Bolts (Step 2): 177.0 Nm (130.0 lb-ft)
Main Bearing Cap Bolts: 177.0 Nm (130.0 lb-ft)
Connecting Rod Cap Bolts: 100.0 Nm (74.0 lb-ft)
Flywheel Bolts: 120.0 Nm (88.5 lb-ft)
Crankshaft Pulley Bolt: 200.0-220.0 Nm (148.0-162.0 lb-ft)
Injection Pump Drive Gear Nut: 60.0-70.0 Nm (44.0-52.0 lb-ft)
Injector Hold-Down Bolts: 60.0-70.0 Nm (44.0-52.0 lb-ft)
Rocker Arm Shaft Bracket Bolts: 40.0-50.0 Nm (30.0-37.0 lb-ft)
Oil Pan Bolts: 20.0-25.0 Nm (15.0-18.0 lb-ft)
Water Pump Bolts: 20.0-25.0 Nm (15.0-18.0 lb-ft)
The Mitsubishi 4D31T engine was widely utilized across automotive,
construction, and industrial equipment applications during its
production run from approximately 1985 to 1996.
Medium-Duty Trucks: Mitsubishi Fuso Canter (FE series, 5th generation),
produced from approximately July 1986 with power output of 117 hp/86 kW
at 3500 rpm. Used in dump truck configurations with 6-ton payload
capacity.
Excavators: Kato HD400VII and HD400VII EXCEED, 10-ton class tracked
excavators producing 61.1 kW (81.9 hp) at 2100 rpm.
Excavators: Alternative applications with power rating of 65 kW (87 hp)
at 2100 rpm.
Tracked Dumpers: Morooka MST 600, producing 87 hp at 2800 rpm.
Industrial Equipment: Various Kobelco excavators and other construction
machinery requiring a 3.3L turbocharged diesel power unit.
Generator Sets: Stationary industrial generator drive units.
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