Mitsubishi 4D68 Specifications
| Engine Model: Mitsubishi 4D68 |
| Engine Type: 4-cycle inline 4-cylinder full-pressure lubrication liquid-cooled diesel |
| Total Displacement: 121.9 cu.in (1.99 L) |
| Rated Engine Power: 85-91 Hp (63-68 kW) at 4500 rpm |
| Fuel System Type: Indirect fuel injection |
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The Mitsubishi 4D68 is a 1.8-liter inline
four-cylinder, four-stroke, water-cooled diesel engine developed as part
of Mitsubishi’s D-series small and medium-capacity diesel family.
Introduced in the early 1990s, it was designed for compact and mid-size
passenger vehicles, providing a balance of reliability, fuel economy,
and simplicity.
The 4D68 is an indirect-injection diesel engine
using a swirl-chamber combustion system, emphasizing smooth operation
and low noise compared to older direct-injection designs of its time. It
was primarily fitted to models such as the Mitsubishi Lancer, Mirage,
Colt, and Galant, serving markets that demanded economy and long service
life rather than high power.
Constructed with a cast-iron cylinder block and aluminum-alloy cylinder
head, the 4D68 was engineered for durability and easy maintenance. Its
overhead camshaft (SOHC) valvetrain operates via a toothed timing belt,
and the engine features two valves per cylinder.
It uses a conventional mechanically governed
distributor-type injection pump, with variants utilizing electronically
assisted fuel control systems in later years. The engine is known for
its dependability and moderate performance, delivering output suitable
for daily transportation and commercial use with minimal servicing
requirements.
The 4D68 is part of the evolutionary line between the older 4D65 and the
later 4D68T (turbocharged) engines. It was widely recognized for
excellent fuel efficiency, achieving low specific fuel consumption and
long operational life when maintained properly. Its conservative design
prioritizes durability, making it a popular choice in Asian, European,
and some export markets during its production run.
The Mitsubishi 4D68 has a displacement of 1,998 cc (2.0 liters or 121.9
cubic inches), achieved through a bore of 82.7 mm (3.26 inches) and a
stroke of 93.0 mm (3.66 inches). The long-stroke configuration
contributes to strong low-end torque typical of diesel engines. The
compression ratio is approximately 22.4:1, which promotes efficient
combustion of diesel fuel in the pre-combustion chamber.
The engine’s firing order is 1–3–4–2, and it operates on the four-stroke
diesel cycle: intake, compression, power, and exhaust. The crankshaft is
supported by five main bearings, ensuring rigidity and smooth operation.
Maximum power output for the naturally aspirated 4D68 is around 63 to 68
kW (85 to 91 Hp, 84 to 90 bhp) at approximately 4,500 revolutions per
minute. Peak torque is in the range of 135 to 138 Nm (99 to 102 lb-ft)
at around 2,500 rpm. Idle speed is set between 750 and 850 rpm.
The engine block is made of high-strength cast iron for rigidity and
wear resistance, while the cylinder head is aluminum alloy to improve
heat dissipation. Each cylinder has a pre-combustion chamber cast into
the head, where initial fuel ignition occurs before expanding into the
main chamber. This indirect-injection arrangement results in smoother
operation and lower combustion noise compared to direct-injection
diesels.
The pistons are aluminum alloy with steel struts for thermal expansion
control, and feature two compression rings and one oil control ring. The
connecting rods are forged steel with a split big-end design. Valve
actuation is via rocker arms driven by a single overhead camshaft, which
is belt-driven from the crankshaft. Hydraulic tappets are not employed;
valve clearance is adjusted manually through screw-and-locknut
adjusters.
The standard redline is around 5,000 rpm, with fuel cut-off near 5,200
rpm under no-load conditions. The engine conforms to Euro 1/2 emission
standards in its original configuration, depending on market and
production year.
The 4D68 uses a conventional mechanically controlled indirect injection
system. Fuel is drawn from the tank by a feed pump and delivered to a
rotary-type (distributor) injection pump manufactured by Mitsubishi or
licensed Bosch VE design. The pump pressurizes the fuel and meters the
quantity according to engine speed and load. Fuel is then distributed to
each cylinder through high-pressure steel injection pipes to pintle-type
injectors.
Injection pressure is typically around 13 to 16 Mpa (1,885 to 2,320
psi). Injection timing is controlled mechanically by the governor
mechanism within the pump, though later electronically assisted versions
use a solenoid to fine-tune timing and quantity for emission control.
The injectors are mounted vertically into the cylinder head and spray
directly into the pre-combustion chamber.
The fuel filter is a replaceable cartridge-type with a water separator.
Replacement is recommended every 40,000 km (25,000 miles). Air is
removed from the system through a manual priming pump integrated into
the filter assembly. Fuel return lines route excess fuel from injectors
and pump back to the tank. Recommended fuel is automotive-grade diesel
meeting ASTM D975 or EN 590 specification.
The fuel system is robust and tolerant of moderate fuel quality, but
consistent use of clean, low-sulfur diesel and regular filter
replacement are essential for long injector and pump life.
The lubrication system of the 4D68 is a fully pressurized wet-sump type.
A trochoid oil pump, driven by the crankshaft via gears, draws oil
through a pickup strainer and delivers it to the main oil gallery. The
gallery supplies oil to the crankshaft main bearings, connecting rod
journals, camshaft bearings, and rocker gear. A full-flow paper-element
oil filter is installed on the side of the block for easy replacement.
Oil pressure at idle is approximately 100 kPa (14.5 psi), and at 3,000
rpm it rises to around 400 kPa (58 psi). The oil capacity with filter
replacement is about 4.5 liters (4.8 US quarts or 4.0 Imperial quarts).
The recommended oil viscosity is SAE 10W-30, 10W-40, or 15W-40 meeting
API CD, CE, or CF standards.
A positive crankcase ventilation (PCV) system recycles blow-by gases to
the intake manifold, maintaining internal cleanliness and reducing
emissions. The oil filler cap is located on the valve cover, and the
dipstick is placed conveniently for regular checks.
Regular oil and filter changes every 7,500 to 10,000 km (4,500 to 6,000
miles) are critical for engine longevity, especially since
indirect-injection diesels generate soot particles that can degrade oil
more rapidly than gasoline engines.
The cooling system is a water-cooled, pressurized, and
forced-circulation type. A belt-driven centrifugal water pump 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 by 95°C (203°F). The radiator is cross-flow aluminum with plastic
end tanks and includes a cap rated around 88 kPa (13 psi).
The cooling fan is mechanically driven on early applications and
electrically controlled on later models. The total coolant capacity is
about 6.0 liters (6.3 US quarts, 5.3 Imperial quarts). The recommended
coolant mixture is a 50/50 blend of ethylene glycol antifreeze and
distilled water, protecting against freezing down to –35°C (–31°F) and
corrosion.
A coolant temperature sensor provides feedback for glow plug control and
dashboard gauge operation. Proper cooling system maintenance -
particularly timely coolant replacement every 40,000 km (25,000 miles)
or two years - is important to prevent corrosion in the aluminum head
and to maintain stable combustion temperature.
| Intake and Exhaust Systems |
The air intake system includes a dry-type replaceable paper air filter
housed in a plastic or metal airbox, connected to a resonance chamber to
reduce induction noise. The intake manifold is made of cast aluminum and
designed to enhance swirl motion for better fuel-air mixing.
The exhaust manifold is cast iron and directs gases through a downpipe
to a catalytic converter (on emission-controlled variants) and muffler.
Exhaust gas recirculation (EGR) is fitted on many 4D68 engines to lower
nitrogen oxide emissions by reintroducing a portion of exhaust gas into
the intake manifold. The EGR valve is vacuum-operated and modulated
according to load and temperature.
The intake and exhaust systems together contribute to low combustion
noise and smooth performance, characteristic of the engine’s
indirect-injection design.
The electrical system operates on 12 volts DC. The alternator is rated
between 65 and 80 amperes, driven by a serpentine or V-belt. The starter
motor is a reduction-gear type rated at approximately 1.4 kW (1.9
horsepower).
For cold starting, the engine employs a glow plug system with four
fast-heating glow plugs mounted in the pre-combustion chambers. The glow
plug relay and timer unit automatically control preheat and after-glow
durations based on coolant temperature. A dashboard indicator shows glow
status.
Battery capacity is usually 60 to 70 ampere-hours. Proper battery
maintenance is essential for reliable cold starts, as diesel engines
require higher cranking torque compared to gasoline engines.
| Valve Timing and Drive Mechanism |
The 4D68 uses a toothed rubber timing belt to drive the camshaft from
the crankshaft. The belt also drives the water pump. Belt tension is
maintained by a spring-loaded tensioner pulley. Replacement of the
timing belt is recommended every 100,000 km (60,000 miles) or sooner if
exposed to severe conditions.
Camshaft timing marks are provided for easy alignment during belt
replacement. The injection pump is also belt-driven and must be timed
precisely using alignment marks to ensure correct injection timing.
Incorrect belt installation or timing misalignment can cause rough
running or starting difficulty.
Overall length of the 4D68 engine assembly is approximately 680 mm (26.8
inches), width 580 mm (22.8 inches), and height 700 mm (27.6 inches).
Dry weight is about 165 kg (364 lbs). The engine mounts use three
rubber-isolated supports to minimize vibration transmission to the
chassis. Compact dimensions allow installation in transverse or
longitudinal configurations depending on the vehicle.
Engine oil and filter: replace every 7,500–10,000 km (4,500–6,000 miles)
or six months.
Air filter: inspect every 10,000 km (6,000 miles) and replace every
30,000 km (18,000 miles).
Fuel filter: replace every 40,000 km (25,000 miles).
Coolant: replace every 40,000 km (25,000 miles) or two years.
Timing belt: replace every 100,000 km (60,000 miles) together with
tensioner and idler.
Glow plugs: inspect every 40,000 km (25,000 miles).
Valve clearance: check and adjust every 40,000 km (25,000 miles).
Compression pressure when new should measure approximately 2,950 kPa
(428 psi) at 300 rpm, with a service limit of 2,400 kPa (348 psi).
Maximum difference between cylinders should not exceed 300 kPa (43 psi).
Idle speed is 800 ± 50 rpm, and injection timing is 5° before top dead
center (BTDC) at idle.
Cylinder head bolts: Stage 1 – 49 Nm (36 lb-ft); Stage 2 – additional 90
degrees; Stage 3 – additional 90 degrees.
Main bearing cap bolts: 68 Nm (50 lb-ft).
Connecting rod bolts: 44 Nm (32 lb-ft) plus 90 degrees.
Camshaft bearing cap bolts: 12 Nm (9 lb-ft).
Flywheel bolts: 83 Nm (61 lb-ft) plus 90 degrees.
Crankshaft pulley bolt: 180 Nm (133 lb-ft).
Injection pump mounting bolts: 22 Nm (16 lb-ft).
Intake manifold bolts: 25 Nm (18 lb-ft).
Exhaust manifold nuts: 35 Nm (26 lb-ft).
Oil drain plug: 40 Nm (30 lb-ft).
Glow plugs: 15 Nm (11 lb-ft).
Valve cover bolts: 9 Nm (7 lb-ft).
The Mitsubishi 4D68 engine was installed in
a range of Mitsubishi passenger and light commercial vehicles from the
early 1990s through the 2000s, including:
– Mitsubishi Lancer (CB, CK, and CM series)
– Mitsubishi Mirage and Colt (CC, CJ series)
– Mitsubishi Galant (E5–E7 series)
– Mitsubishi Carisma (European markets)
– Proton Wira 2.0D (licensed application)
– Hyundai Elantra Diesel (under technology license)
Its moderate size, economy, and durability made it suitable for both
front-wheel-drive and rear-wheel-drive configurations. Production
continued in some markets for several years due to its reliability and
fuel efficiency.
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