| Home / Car Engines / Mitsubishi Engines / Mitsubishi 4M40 |
Mitsubishi 4M40 Specifications
| Engine Model: Mitsubishi 4M40 |
| Engine Type: 4-cycle inline 4-cylinder full-pressure lubrication liquid-cooled diesel |
| Total Displacement: 173 cu.in (2.83 L) |
| Rated Engine Power: 75-140 Hp (56-104 kW) at 4000 rpm |
| Fuel System Type: Direct fuel injection |
____________________________________________________________________________________
- Mitsubishi 4D56 Engine Specifications
- Mitsubishi 4D68 Engine Specifications
- Mitsubishi 4DR5 Engine Specifications
| General Technical Data |
The Mitsubishi 4M40 is a highly respected four-cylinder diesel engine widely used in SUVs, light commercial vehicles, and industrial equipment. Introduced in the early 1990s, it powered the Mitsubishi Pajero, Delica, Challenger, and various export-market utility vehicles. Built with a rugged cast-iron block, an aluminum cylinder head, and a mechanically governed direct-injection system in early versions, the 4M40 earned a reputation for torque-rich performance, long-term durability, and ease of maintenance.
Later variants adopted electronically
controlled injection pumps to improve emissions, refinement, and fuel
economy. Turbocharging and intercooling were applied to many versions,
giving the engine strong pulling power suited for off-road use and
towing. The 4M40 became famous for its robust design and ability to
operate reliably in harsh climates, remote regions, and demanding
commercial environments.
The 4M40 is a four-stroke, water-cooled, inline four-cylinder diesel
engine. Total displacement is 2,835 cubic centimeters (173 cubic
inches). Bore is 95.0 millimeters (3.74 inches) and stroke is 100.0
millimeters (3.94 inches). This slightly undersquare configuration
favors torque at low and mid-range engine speeds. Compression ratio
varies depending on the version: early mechanical-injection models
typically use around 21.0:1, while electronic versions often use
approximately 21.5:1.
Power output depends heavily on
turbocharging and intercooling:
– Naturally aspirated variants: approximately 75–85 horsepower (56–63
kW) at around 4,200 rpm.
– Turbocharged non-intercooled versions: typically 100–120 horsepower
(75–88 kW) at 4,000 rpm.
– Turbocharged and intercooled versions: generally 125–140 horsepower
(93–104 kW) at 4,000 rpm.
Peak torque also varies:
– Naturally aspirated: 160–180 N·m (118–133 lb·ft) at 2,000 rpm.
– Turbocharged non-intercooled: 240–260 N·m (177–192 lb·ft) at 2,000
rpm.
– Turbo-intercooled: 290–330 N·m (214–243 lb·ft) at 2,000 rpm.
The firing order is 1–3–4–2. Idle speed is typically 750 ± 50 rpm.
Redline is generally limited to about 4,500 rpm, with governed maximum
speed near 4,200–4,400 rpm depending on application. The crankshaft is a
forged-steel unit supported by five main bearings. Pistons are
cast-aluminum alloy with reinforced crowns and combustion bowls designed
to optimize air swirl and fuel atomization. Piston rings include 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 deep ribbing for strength, thermal
stability, and vibration control. Coolant passages are arranged to
maintain consistent temperatures around the cylinder walls. The
crankcase structure provides the rigidity necessary for turbocharged
operation. Oil galleries distribute pressurized lubrication to the
crankshaft, connecting rods, and camshaft bearings. Engine mounting
bosses accommodate a variety of vehicle platforms, allowing installation
in longitudinal or transverse arrangements depending on specific model
requirements.
The cylinder head is made of aluminum alloy to reduce weight and improve
heat dissipation. It contains pre-combustion chambers in older variants
that use indirect injection, while direct-injection versions use
redesigned combustion bowls in the piston and matched injector spray
patterns. The head features overhead valves actuated through pushrods
and rocker arms from a single camshaft located in the block. Valve seats
are hardened steel for durability. Valve clearances are manually
adjustable.
Cold specifications:
– Intake valves: 0.20–0.30 mm (0.008–0.012 in)
– Exhaust valves: 0.30–0.40 mm (0.012–0.016 in)
| Fuel System |
Early 4M40 engines use a fully mechanical direct-injection system with a rotary or inline high-pressure injection pump. Later versions incorporate electronically controlled fuel-injection pumps that regulate timing and fuel quantity more precisely, improving emissions and response.
Fuel flow begins with a mechanical lift pump sending diesel through a
sediment bowl or water separator, then through a fine paper-element
filter. The high-pressure pump meters fuel delivery and sends it to
multi-hole injectors, which atomize fuel directly into the combustion
chamber.
Injection pressure depends on pump type but typically ranges from
250–350 bar for mechanical systems and slightly higher for electronic
versions. The fuel system is designed to tolerate moderate contamination
but performs best with clean diesel of at least 45 cetane. Maintenance
includes replacing filters every 10,000–15,000 km and servicing
injectors every 40,000–60,000 km.
| Lubrication System |
A full-pressure wet-sump lubrication system ensures proper engine
protection. A gear-driven oil pump draws oil from the sump through a
pickup screen and sends it through a full-flow spin-on filter.
Pressurized oil lubricates main bearings, connecting-rod journals,
camshaft bearings, rocker gear, turbocharger bearings, and auxiliary
drives. Some variants incorporate piston-cooling oil jets to reduce
crown temperatures during heavy use.
Oil capacity is 6.5–7.5 liters (6.9–7.9 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 grades include SAE 15W-40, 10W-30,
or 20W-50 depending on climate. Oil changes are normally recommended
every 5,000–7,500 km or 200–250 hours for industrial service.
| Cooling System |
Cooling is provided by a closed-loop, forced-circulation liquid cooling system. A belt-driven centrifugal water pump circulates coolant through the block, head, radiator, and heater core. A thermostat opens at approximately 82°C (180°F) and is fully open near 95°C (203°F).
Coolant capacity is approximately 8–9 liters (8.4–9.5 US quarts). System
pressure is typically maintained at 70–90 kPa (10–13 psi). A 50/50
mixture of ethylene glycol antifreeze and distilled water is
recommended.
Turbocharged variants may include an additional oil cooler or
water-cooled turbocharger to ensure thermal stability. Intercooled
models include a front-mounted or top-mounted air-to-air intercooler to
reduce intake air temperature and improve combustion efficiency.
| Intake and Exhaust Systems |
Air intake filtration varies by application. Automotive installations use dry-element air filters for low restriction, while industrial units may use multi-stage cyclone or oil-bath filters for severe environments. Intake manifolds are cast aluminum or steel depending on version.
Turbocharged variants use a compressor housing connected to the intake
manifold through aluminum or rubber ducting. Intercooled models route
intake charge air through an intercooler before entering the intake
manifold.
The exhaust manifold is cast iron and engineered to withstand constant
thermal cycling. Turbocharged models mount the turbocharger directly to
the exhaust manifold. Industrial or marine applications may include
large mufflers, spark arrestors, or vertical exhaust stacks.
| Electrical System |
Depending on vehicle or industrial specification, the electrical system may be 12 or 24 volts. Alternators are typically rated 60–90 amperes. Starter motors range from 2.0–3.0 kW. Glow plugs or intake heaters assist with cold starting.
Electronic fuel-pump versions incorporate an ECU controlling injection timing, fuel delivery, idle stability, boost control, and emissions functions. Sensors include coolant temperature, intake air temperature, crank position, boost pressure, throttle position, and fuel temperature sensors.
| Other Systems |
The 4M40 may support hydraulic pump drives, vacuum pumps for brake boosters, air-conditioning compressors, power-steering pumps, marine cooling heat exchangers, and PTO equipment. Many engines include oil coolers and external cooling ports for industrial equipment.
| Dimensions and Weight |
– Length: 750–800 mm (29.5–31.5 in)
– Width: 600–650 mm (23.6–25.6 in)
– Height: 780–830 mm (30.7–32.7 in)
Dry weight ranges from 240–280 kg (529–617 lb) depending on
turbocharging and accessories.
| Maintenance Data |
– 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
– Timing chain inspection: 100,000 km
– Compression test: every 100,000 km
| Tightening Torques |
– Cylinder head bolts: initial torque 39 Nm (29 lb-ft), second stage 98
Nm (72 lb-ft), then additional 90 degrees of rotation.
– Main bearing cap bolts: 93 Nm (69 lb-ft).
– Connecting rod bolts: 49 Nm (36 lb-ft) plus 90 degrees.
– Camshaft bearing cap bolts: 14 Nm (10 lb-ft).
– Flywheel bolts: 108 Nm (80 lb-ft) plus 90 degrees.
– Crankshaft pulley bolt: 216 Nm (159 lb-ft).
– Oil pump cover bolts: 10 Nm (7 lb-ft).
– Intake manifold bolts: 25 Nm (18 lb-ft).
– Exhaust manifold nuts: 35 Nm (26 lb-ft).
– Valve cover bolts: 9 Nm (7 lb-ft).
– Oil drain plug: 40 Nm (30 lb-ft).
– Glow plugs: 13 Nm (10 lb-ft).
| Vehicle Applications |
The 4M40 engine is widely used in:
– Mitsubishi Pajero / Montero
– Mitsubishi Delica
– Mitsubishi Challenger / Pajero Sport
– Various commercial trucks and vans
– Industrial equipment, generators, pumps
– Marine auxiliary drives
____________________________________________________________________________________
| Car Engines Technical Specifications |
| Small Engines Technical Specifications |
| Industrial Engines Technical Specifications |
| Outboard Engines Technical Specifications |