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Mitsubishi 4D30 Specifications
| Engine Model: Mitsubishi 4D30 |
| Engine Type: 4-cycle inline 4-cylinder full-pressure lubrication liquid-cooled diesel |
| Total Displacement: 201.2 cu.in (3.29 L) |
| Rated Engine Power: 85-95 Hp (63-71 kW) at 3200 rpm |
| Fuel System Type: Indirect or direct fuel injection |
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| General Technical Data |
The Mitsubishi 4D30 is a durable, medium-displacement diesel engine developed for light trucks, commercial vehicles, and industrial equipment. As part of Mitsubishi’s long-running 4D-series of diesel powerplants, the 4D30 was engineered to deliver dependable torque, low fuel consumption, and exceptional reliability under harsh operating conditions.
Its rugged mechanical design, cast-iron construction, direct-injection capability in later versions, and simple serviceability earned it a strong reputation in markets requiring robust engines for cargo hauling, municipal fleets, and agricultural machinery.
Designed for continuous-duty applications, the
4D30 emphasizes thermal stability, mechanical longevity, and ease of
overhaul. Although not designed for high performance, it excels in
environments where steady low-end power, operational economy, and long
service intervals are essential.
The Mitsubishi 4D30 is a four-cylinder, inline diesel engine with a
displacement of approximately 3,298 cc (3.3 liters or 201.2 cubic
inches). Bore typically measures 100 mm (3.94 inches), while stroke is
about 105 mm (4.13 inches), forming a long-stroke configuration
optimized for high torque output at low and mid-range engine speeds.
Depending on configuration and emissions requirements, compression ratio usually ranges from 18.0:1 to 20.0:1. Power output typically falls between 85 and 95 horsepower (63 to 71 kW) at around 3,200 rpm, while torque averages between 200 and 240 Nm (148 to 177 lb-ft) at 1,800-2,000 rpm. The engine design prioritizes steady pulling power and fuel efficiency over high-rev performance.
Idle speed normally sits around 650-750 rpm.
The firing order is 1-3-4-2, standard for inline-four diesel engines.
Redline is relatively low compared to gasoline engines, usually near
3,500 rpm, reflecting the engine-s heavy-duty torque-oriented nature.
The cylinder block of the Mitsubishi 4D30 is constructed from cast iron
for maximum rigidity, durability, and thermal stability. The block
features deep external ribbing to resist stress under continuous heavy
load. Mitsubishi designed the block to withstand high combustion
pressures characteristic of diesel operation. The forged-steel
crankshaft is supported by five large main bearings, providing strength
and consistent lubrication across all load conditions.
The crankshaft uses counterweights to maintain rotational balance and reduce vibration. Pistons are cast-aluminum alloy with reinforced crowns designed to withstand elevated combustion temperatures. Many versions incorporate internal oil-cooling galleries within the pistons.
The connecting rods are forged steel with
replaceable bearings to facilitate overhaul. Cylinder liners are
typically dry-type for ease of servicing. The block-s oiling passages
are engineered to feed the crankshaft, camshaft, and valvetrain with
stable oil pressure.
The cylinder head is made from cast iron to withstand extreme thermal
cycling. Depending on the version, the 4D30 may use an
indirect-injection (IDI) or direct-injection (DI) combustion system. IDI
versions feature pre-combustion chambers designed for smoother
combustion and easier cold starts, while DI versions improve fuel
efficiency and torque output.
The valvetrain uses an overhead valve (OHV) configuration with a camshaft mounted within the block. The camshaft drives the valves through pushrods and rocker arms. This mechanically straightforward design enhances durability, simplifies maintenance, and improves engine longevity.
Valve seats and guides are hardened to resist wear under high heat. The head gasket is designed to endure diesel compression and must be replaced with care during engine rebuilds. Glow plugs are fitted to assist cold starts in colder climates, especially on IDI variants.
| Fuel System |
The Mitsubishi 4D30 uses a mechanically governed diesel fuel-injection system. Fuel delivery begins with a mechanical lift pump feeding a primary sediment bowl or water separator, followed by a fine paper-element secondary filter. From here, fuel flows to a high-pressure injection pump-typically an inline Bosch-type or Zexel pump-which meters fuel quantity and timing. Injectors may be pintle-type for IDI variants or multi-hole nozzles for DI versions.
Injection pressures typically range between 160 and 250 bar depending on configuration. The mechanical governor maintains stable rpm under varying loads and ensures predictable throttle response. Fuel atomization quality is critical for efficient diesel combustion, and Mitsubishi engineered the injector nozzles for stable spray patterns and reliability. The system is known for its durability even in regions with variable fuel quality.
| Lubrication System |
The lubrication system is a full-pressure, wet-sump design featuring a gear-driven oil pump located at the bottom of the engine. The pump draws oil from the sump through a metal mesh pickup and forces it through a full-flow spin-on oil filter before distributing it through internal galleries. Oil reaches the crankshaft bearings, connecting-rod journals, camshaft, rocker system, and auxiliary components.
Operating oil pressure typically ranges from 300 to 450 kPa (44 to 65 psi) at cruising speed, with idle pressure around 100 kPa (15 psi). Oil capacity varies slightly depending on model and oil pan design but is usually around 6.5 to 7.5 liters (6.9 to 7.9 US quarts). Recommended oil viscosities include SAE 15W-40 or 20W-50 diesel oils meeting API CF or higher standards. A PCV or draft-tube system prevents pressure buildup inside the crankcase.
| Cooling System |
The cooling system is a forced-circulation, liquid-cooled design consisting of a belt-driven centrifugal water pump, cast-iron coolant passages, an aluminum radiator, and a wax-type thermostat. Coolant flows through the block and head to manage internal temperatures and prevent overheating during prolonged high-load operation. The thermostat begins opening around 82°C (180°F) and reaches full operation near 95°C (203°F).
Cooling system capacity ranges between 8 and 10 liters (8.4 to 10.5 US quarts). System pressure ranges around 70 to 90 kPa (10 to 13 psi). Coolant mixture is typically a 50/50 blend of ethylene glycol and distilled water. Some industrial versions include larger radiators or oil coolers for enhanced thermal regulation in continuous-duty cycles. Proper cooling-system maintenance is crucial given the thermal loads associated with diesel combustion.
| Intake and Exhaust Systems |
The induction system generally includes a dry air filter, intake ducting, and a cast-aluminum or cast-iron intake manifold. Some industrial variants may use cyclone-type pre-filters for dusty environments. Turbocharging was available in later or higher-output variants of related 4D engines, but the standard 4D30 is naturally aspirated.
The exhaust system includes a thick-walled cast-iron exhaust manifold designed to withstand high thermal strain. Exhaust routing varies by application: trucks often use compact systems, while industrial models may employ large mufflers or vertical exhaust stacks. Emissions control is basic, typically limited to proper fuel metering and clean combustion; older 4D30 engines predate modern emissions regulations.
| Electrical System |
The electrical system generally operates on 12 volts for road-going vehicles and sometimes 24 volts for industrial applications. The alternator typically supplies between 40 and 60 amperes depending on configuration. The starter motor is usually rated between 2.0 and 3.0 kW, providing strong cranking torque for cold starts.
Glow plugs or intake-heater systems assist ignition in cold climates. Wiring harnesses are ruggedized to withstand vibration, dust, and temperature fluctuations. The engine uses minimal electronic control, making it easy to diagnose and repair in field conditions.
| Other Systems |
Depending on vehicle application, the 4D30 may drive accessories such as hydraulic pumps, power-steering pumps, vacuum pumps for brake boosters, or air compressors for pneumatic systems. PTO (power take-off) units are commonly mounted for auxiliary equipment. The crankcase ventilation system varies between open-type and semi-closed depending on regulations and model year.
Some industrial configurations include dual-stage fuel filtration, remote oil coolers, and heavy-duty air-filtration systems. The simplicity of the mechanical systems allows the engine to operate reliably in difficult environments with minimal support infrastructure.
| Dimensions and Weight |
The Mitsubishi 4D30 engine is medium-sized relative to its displacement category. Typical overall length ranges from 720 to 780 mm (28.3 to 30.7 inches), width from 600 to 650 mm (23.6 to 25.6 inches), and height from 750 to 800 mm (29.5 to 31.5 inches). Dry weight usually falls between 200 and 240 kg (441 to 529 lbs), depending on accessory configuration and oil-pan style. Its compact yet heavy-duty construction enables easy installation in light trucks and industrial machinery. Engine weight also contributes to vehicle stability when used in commercial trucks.
| Maintenance Data |
Oil and filter changes are recommended every 5,000 to 7,500 km (3,000 to 4,600 miles) or every 200-250 operating hours in industrial environments. Fuel filters should be replaced every 10,000 to 15,000 km (6,200 to 9,300 miles). Air-filter service intervals vary depending on dust levels but fall between 8,000 and 12,000 km (5,000 to 7,500 miles).
Coolant should be replaced every two years or every 30,000 km (18,600 miles). Valve lash should be adjusted every 15,000 to 20,000 km (9,300 to 12,400 miles). Injector servicing is recommended every 40,000 to 60,000 km (25,000 to 37,000 miles). A compression test is advisable at 100,000 km (62,000 miles) to assess internal wear.
| Tightening Torques |
Cylinder-head bolts require tightening in multiple stages, reaching approximately 110 to 130 Nm (81 to 96 lb-ft). Main-bearing-cap bolts usually tighten to 110 to 130 Nm (81 to 96 lb-ft). Connecting-rod bolts require about 55 to 65 Nm (41 to 48 lb-ft). Flywheel bolts tighten to around 100 to 120 Nm (74 to 89 lb-ft).
The crankshaft-pulley bolt may require up to 150 to 170 Nm (111 to 125 lb-ft). The oil-drain plug torque is 35 to 45 Nm (26 to 33 lb-ft). Injector hold-down bolts require 20 to 25 Nm (15 to 18 lb-ft). Glow plugs tighten to around 10 to 15 Nm (7 to 11 lb-ft).
| Vehicle Applications |
The Mitsubishi 4D30 engine was widely used
in:
- Mitsubishi Canter light trucks
- Mitsubishi Rosa minibuses
- Various Asian and Middle Eastern commercial trucks
- Industrial machinery such as generators, compressors, and pumps
- Agricultural equipment and off-road utility vehicles
- Municipal service vehicles
The engine-s reliability, ease of overhaul, and low fuel consumption
made it a highly desirable powerplant in demanding commercial and
industrial markets.
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