Mitsubishi 6D14 Specifications
| Engine Model: Mitsubishi 6D14 |
| Engine Type: 4-cycle inline 6-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 399.5 cu.in (6.55 L) |
| Rated Engine Power: 135-155 Hp (100-116 kW) at 2800 rpm |
| Fuel System Type: Direct fuel injection |
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The Mitsubishi 6D14 is a mid-displacement
inline-six diesel engine developed for medium-duty commercial trucks,
buses, construction machinery, industrial equipment, and power units.
Part of Mitsubishi’s long-running 6D-series family, the 6D14 is renowned
for mechanical simplicity, robust cast-iron construction, long service
life, and torque-rich performance at low and mid-range engine speeds.
This engine was widely used in the Mitsubishi Fuso Fighter series and
various export-market trucks during the 1980s and 1990s, helping build
Mitsubishi’s reputation for reliable workhorse engines suited for harsh
environments, long-haul duty, and heavy payloads.
Built with a gear-driven camshaft, mechanical direct-injection fuel
system, and conservative component design, the 6D14 is capable of
sustaining long periods of continuous operation under demanding
conditions.
Operators value it for ease of maintenance, tolerance to variable fuel
quality, and resistance to overheating thanks to its high-capacity
cooling system. The 6D14 occupies a key role in Mitsubishi’s history as
one of the engines that made the company globally competitive in
commercial diesel technology.
The Mitsubishi 6D14 is a four-stroke, water-cooled, inline six-cylinder
diesel engine. Total displacement is 6,550 cc (399.5 cubic inches). Bore
is 110 mm (4.33 inches), and stroke is 115 mm (4.53 inches), giving the
engine a long-stroke configuration optimized for high torque production.
The compression ratio is 17.0:1 to 18.0:1 depending on model year and
emissions calibration.
Power output varies by market and
configuration:
- Naturally aspirated versions produce 135-155 Hp (100-116 kW) at around
2,800 rpm.
- Later turbocharged industrial variants may reach slightly higher
output depending on calibration.
Peak torque generally falls between 380 and 450 Nm (280-332 lb-ft) at
approximately 1,600-1,800 rpm. The firing order is 1-5-3-6-2-4. Idle
speed is 650-750 rpm, with governed maximum speed around 2,800-3,000 rpm
for automotive versions and lower limits for industrial constant-speed
applications.
The crankshaft is a forged-steel, fully counterweighted unit supported
by seven large main bearings for excellent rotational stability. Pistons
are cast-aluminum alloy with reinforced crowns and deep combustion
bowls. The piston ring pack consists of two compression rings and one
oil-control ring. Connecting rods are forged steel with replaceable
big-end bearings.
The cylinder block is cast iron with thick walls and extensive ribbing
to ensure rigidity and minimize vibration under heavy load. The
crankcase structure is deeply reinforced, supporting the heavy rotating
mass associated with a long-stroke six-cylinder engine. Coolant passages
are cast into the block to maintain even cylinder temperature.
The block includes mounting bosses for power steering pumps, air
compressors, hydraulic pumps, and industrial accessories. Oil galleries
circulate lubrication throughout the engine, feeding bearings,
valvetrain components, and auxiliary systems.
The cylinder head is cast iron for durability and thermal stability. It
contains direct-injection combustion chambers shaped for efficient fuel
atomization and swirl. The valvetrain uses a camshaft located in the
block, with pushrods and rocker arms actuating overhead valves. Valve
seats are hardened steel inserts to withstand high combustion
temperatures. Valve clearances are manually adjustable.
Cold lash settings are:
- Intake: 0.25-0.30 mm (0.010-0.012 in)
- Exhaust: 0.35-0.40 mm (0.014-0.016 in)
The 6D14 uses a fully mechanical direct-injection fuel system. A
mechanical lift pump draws diesel from the fuel tank through a primary
sediment bowl or water separator. A secondary fine-element fuel filter
provides further cleaning before the fuel enters the high-pressure
injection pump. Depending on production year, the 6D14 may use an inline
mechanical pump or a rotary distribution-type pump. Injection pressures
fall in the 250-350 bar range.
Injectors are multi-hole mechanical units designed to deliver finely
atomized fuel into the piston combustion bowls. Fuel timing is
mechanically controlled and must be set accurately during major service.
The system is known for reliability and tolerance of variable fuel
quality.
Fuel maintenance intervals:
- Fuel filters: every 10,000-15,000 km
- Injector servicing: every 40,000-60,000 km
- Water separator draining: as required
- Pump timing checks: at major service intervals
The lubrication system is a full-pressure wet-sump type. 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. Lubrication targets
include crankshaft main bearings, connecting-rod bearings, camshaft
bearings, rocker arms, pushrods, and auxiliary systems. Turbocharged
versions include oil feed and return lines for the turbocharger.
Oil capacity is generally 12-14 liters (12.7-14.8 US quarts). Normal oil
pressure ranges from 300 to 450 kPa (44-65 psi) at operating speed and
around 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: 5,000-7,500 km
- Industrial: 200-250 operating hours
The cooling system is a closed-loop, forced-circulation design with a
belt-driven centrifugal water pump. Coolant flows through the block,
cylinder head, and radiator. A thermostat begins opening at
approximately 82°C (180°F) and is fully open near 95°C (203°F).
Coolant capacity typically ranges from 14-18 liters (14.8-19.0 US
quarts). System pressure is maintained by a radiator cap rated around
70-90 kPa (10-13 psi). A 50/50 mixture of ethylene glycol and distilled
water is recommended for corrosion protection and freeze resistance.
Industrial and constant-duty applications may incorporate larger
radiators, multi-row cooling cores, or oil-to-water heat exchangers to
improve temperature stability.
| Intake and Exhaust Systems |
Air intake filtration varies depending on application. Trucks use
dry-element air filters, while industrial and agricultural equipment may
use oil-bath or cyclone-type pre-cleaners for dusty environments. The
intake manifold is cast iron or aluminum depending on configuration.
Cold-start aids include glow plugs or intake heaters in some variants.
The exhaust manifold is cast iron and designed to withstand prolonged
exposure to high exhaust temperatures. Industrial applications may
include spark arrestors, heavy mufflers, or vertical exhaust stacks.
Electrical specifications vary depending on
installation:
- 12-volt systems for trucks
- 24-volt systems for industrial equipment and buses
Alternators range from 40-80 amperes. Starter motors are rated 2.5-4.0
kW. Glow-plug or intake-heater systems assist with cold starting. The
engine uses minimal electronics, increasing reliability in remote
service areas. Industrial versions may include safety shutdown switches
for oil pressure and coolant temperature.
Depending on application, the 6D14 may
power:
- hydraulic pumps
- vacuum pumps
- air compressors for braking systems
- power steering pumps
- PTO equipment
- marine cooling systems
- Length: 1,050-1,150 mm (41.3-45.3 in)
- Width: 650-750 mm (25.6-29.5 in)
- Height: 900-1,000 mm (35.4-39.4 in)
Dry weight ranges from 480 to 620 kg (1,058-1,367 lbs) depending on
configuration and accessories.
- Engine oil and filter: 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 adjustment: every 15,000-20,000 km
- Injector servicing: every 40,000-60,000 km
- Compression testing: every 100,000 km
- Belt inspection: every service interval
- Cylinder head bolts: 130-150 Nm
- Main bearing caps: 130-150 Nm
- Connecting-rod bolts: 65-75 Nm
- Flywheel bolts: 110-130 Nm
- Crankshaft pulley bolt: 200-220 Nm
- Oil drain plug: 35-45 Nm
- Injector hold-down bolts: 20-25 Nm
- Glow plugs: 10-15 Nm
The Mitsubishi 6D14 engine is widely used
in:
- Mitsubishi Fuso Fighter trucks
- Medium-duty flatbed trucks
- Dump trucks and construction support vehicles
- Buses and passenger transports
- Agricultural machinery
- Industrial power units and generators
- Marine auxiliary engines
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