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Mitsubishi 4B12 Specifications
| Engine Model: Mitsubishi 4B12 |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 143.9 cu.in (2.36 L) |
| Rated Engine Power: 168-177 Hp (125-132 kW) at 6000 rpm |
| Fuel System Type: Sequential multi-point electronic fuel injection |
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| General Technical Data |
The Mitsubishi 4B12 is a 2.4-liter inline-four gasoline engine belonging to the 4B1 series developed jointly by Mitsubishi Motors and Hyundai Motor Company. Introduced in the mid-2000s, it succeeded the older 4G6 family, offering improved efficiency, lighter construction, and compliance with modern emission standards. The 4B12 was engineered for mid-size sedans, crossovers, and compact SUVs, providing a balance between performance, durability, and fuel economy.
With an aluminum block and head, chain-driven
dual overhead camshafts, and variable valve timing (MIVEC), it
represents Mitsubishi’s transition to modern lightweight and
low-emission engine technology. The engine’s design emphasizes long
service life, low maintenance, and compatibility with global fuel
quality standards.
Initially, the 4B12 appeared in standard naturally aspirated
configuration with multi-point electronic fuel injection. Later versions
incorporated Mitsubishi Innovative Valve timing Electronic Control
(MIVEC) on both intake and exhaust camshafts, meeting Euro 4 and Euro 5
emission standards. The MIVEC system improved combustion efficiency,
torque distribution, and reduced fuel consumption under partial load
conditions.
The 4B12’s robust yet lightweight design made
it suitable for a wide range of vehicles, including the Outlander,
Lancer, Galant Fortis, and various PSA models such as the Citroen
C-Crosser and Peugeot 4007 under the Mitsubishi–PSA collaboration. Known
for its smoothness and moderate fuel use, the 4B12 is one of the most
reliable members of Mitsubishi’s modern four-cylinder lineup.
The Mitsubishi 4B12 has a displacement of 2,359 cc (143.9 cubic inches),
achieved through a bore of 88.0 mm (3.46 inches) and a stroke of 97.0 mm
(3.82 inches), giving it a long-stroke configuration that favors torque
over high-end power. The compression ratio is 10.5:1 for standard
versions and up to 10.8:1 in later MIVEC Euro 5 variants.
The cylinder block is made of aluminum alloy
with cast-iron liners inserted by a die-casting process, ensuring
strength and wear resistance while keeping weight low. The crankshaft is
forged steel, supported by five main bearings. Connecting rods are
powder-forged steel, and pistons are lightweight aluminum alloy with
molybdenum-coated skirts to minimize friction.
The DOHC cylinder head is also aluminum alloy, featuring four valves per
cylinder - two intake and two exhaust - actuated by roller rocker arms
and hydraulic lash adjusters. In MIVEC-equipped versions, both camshafts
are variably phased via oil pressure-controlled actuators, continuously
adjusting valve timing according to load and speed. The firing order is
1-3-4-2, with a clockwise crankshaft rotation viewed from the front. The
redline is approximately 6,500 rpm, with fuel cut-off at 6,800 rpm. Idle
speed is regulated electronically around 700 ± 50 rpm.
Power output varies by application and market. Standard 4B12 engines
produce between 125 and 130 kW (168–174 Hp, or 166–172 bhp) at 6,000
rpm. Maximum torque is rated at 226 to 232 Nm (167–171 lb-ft) at 4,100
rpm. Later MIVEC versions optimized for Euro 5 emission standards may
produce up to 177 horsepower (132 kW) with slightly improved torque
spread and fuel economy. The engine meets Euro 4/5/6 emission
regulations depending on calibration, using a three-way catalytic
converter and oxygen sensor feedback for precise mixture control.
| Fuel System |
The 4B12 employs an electronically controlled multi-point fuel injection
system. Fuel is drawn from an in-tank electric pump and supplied under
pressure to the fuel rail, which distributes it to four high-precision
injectors located on the intake manifold. Each injector is controlled
individually by the ECU for accurate timing and pulse width, ensuring
optimal atomization and combustion efficiency. The fuel pressure
regulator maintains approximately 350 kPa (51 psi) under normal
conditions. A manifold absolute pressure sensor, throttle position
sensor, and oxygen sensors provide feedback for closed-loop operation.
Later versions incorporate sequential injection synchronized to each
cylinder’s intake stroke. The system is designed for unleaded gasoline
with a minimum octane rating of 95 RON (91 AKI). Fuel filter replacement
is recommended every 40,000 km (25,000 miles). Injectors are to be
cleaned or serviced every 80,000 km (50,000 miles). The electronic
throttle control (ETACS) replaces mechanical linkage, allowing smoother
throttle modulation and integration with stability and cruise control
systems.
| Lubrication System |
The lubrication system is a fully pressurized wet-sump design using a
trochoid-type oil pump driven by the crankshaft. Oil is drawn from the
sump through a mesh strainer and delivered under pressure to the main
gallery feeding crankshaft bearings, connecting rods, camshafts, and
valve train components. A full-flow spin-on type filter ensures particle
removal, while a bypass valve guarantees lubrication even under filter
clogging. Oil jets under each piston cool the crown area, reducing knock
tendency and thermal load.
Normal oil pressure is approximately 400 to 600 kPa (58–87 psi) at 3,000
rpm and about 100 kPa (15 psi) at idle. Total oil capacity with filter
is 4.3 liters (4.5 US quarts, 3.8 Imperial quarts). Recommended oil
grade is SAE 0W-20, 5W-30, or 10W-30 depending on climate, meeting API
SN or higher standards. Oil and filter changes are specified at every
10,000 km (6,000 miles) or six months under normal service, and more
frequently under severe driving. The PCV (Positive Crankcase
Ventilation) valve integrated in the rocker cover maintains clean
internal pressure and prevents sludge formation.
| Cooling System |
A pressurized liquid cooling system ensures uniform temperature control.
The water pump, driven by the serpentine belt, circulates coolant
through the engine block, cylinder head, radiator, and heater core. The
thermostat starts to open at 82°C (180°F) and is fully open near 95°C
(203°F). A cross-flow aluminum radiator with dual electric fans is used,
with ECU-controlled fan operation based on coolant temperature and air
conditioning demand. The system pressure cap is rated around 108 kPa
(15.6 psi).
Coolant capacity is about 7.0 liters (7.4 US quarts, 6.2 Imperial
quarts). The coolant is a 50/50 ethylene glycol and distilled water
mixture providing freeze protection to –35°C (–31°F). Recommended
coolant replacement interval is every 160,000 km (100,000 miles) or five
years. The coolant temperature sensor provides data to both ECU and
dashboard gauge, ensuring proper regulation of engine temperature and
fan activation.
| Intake and Exhaust Systems |
The intake system employs a composite plastic intake manifold with long,
smoothly curved runners designed to promote strong midrange torque. A
resonator chamber minimizes induction noise. The throttle body is
electronically controlled, featuring an idle control actuator integrated
into the housing. Air passes through a replaceable dry-paper air filter
element, recommended for replacement every 20,000 km (12,000 miles).
The exhaust system consists of a stainless steel or cast iron manifold
feeding a front catalytic converter positioned close to the engine for
rapid warm-up. Downstream oxygen sensors ensure precise air-fuel ratio
monitoring. In MIVEC versions, an EGR (Exhaust Gas Recirculation) system
reintroduces a small amount of exhaust gas to the intake to lower NOx
emissions. A secondary air injection system is used on some Euro 5
engines for quicker catalyst activation during cold starts.
| Ignition and Electrical System |
The ignition system is coil-on-plug type with four individual ignition
coils directly mounted on each spark plug. The ECU controls ignition
timing and dwell individually for each cylinder based on input from
crankshaft and camshaft position sensors, knock sensors, and manifold
pressure. Spark plugs are iridium-tipped for long service life and
consistent spark performance. The specification is NGK ILFR6B or Denso
SK16HR11, gapped at 1.1 mm (0.043 inches). Replacement interval is
100,000 km (62,000 miles).
The alternator is rated between 90 and 110 amperes, depending on
application, while the starter motor is a 1.4 kilowatt reduction-gear
type. The electrical system operates at 12 volts. Battery capacity is
typically 60 Ah. The ECU governs all functions including fuel injection,
ignition, idle speed, and MIVEC phasing.
| Valve Timing and Drive Mechanism |
The 4B12 uses a single-row roller timing chain to synchronize crankshaft and camshafts. Chain tension is maintained automatically by a hydraulic tensioner and guide system. The chain also drives the water pump.
Replacement of the chain is generally not required under normal service, but inspection for elongation is recommended after 200,000 km (124,000 miles). Timing marks on the camshaft and crankshaft sprockets facilitate correct alignment during service.
MIVEC (Mitsubishi Innovative Valve timing Electronic Control) varies valve timing continuously using oil pressure-operated actuators on both camshafts. The ECU adjusts phasing based on engine speed, load, and throttle position, optimizing performance and efficiency. At low rpm, valve overlap is minimized for stability and economy; at higher rpm, overlap increases for improved breathing and power output.
| Other Systems |
The positive crankcase ventilation (PCV) system routes blow-by gases
from the crankcase to the intake manifold for re-combustion, reducing
hydrocarbon emissions. The evaporative emission control (EVAP) system
captures fuel vapors from the tank and directs them into the intake via
a purge control valve. The idle air control is integrated within the
electronic throttle system. The engine incorporates a knock control
system to prevent detonation under high load, dynamically adjusting
ignition timing.
Emissions equipment includes a close-coupled three-way catalytic
converter, two oxygen sensors, and on some Euro 6 versions, a secondary
catalytic converter under the floor. On-board diagnostics (OBD-II)
monitor all major systems, storing trouble codes retrievable via
standard scan tools. The engine also features adaptive learning for idle
speed, MIVEC control, and fuel trim adjustments.
| Dimensions and Weight |
The Mitsubishi 4B12 engine’s external dimensions are approximately 665 mm (26.2 inches) in length, 630 mm (24.8 inches) in width, and 695 mm (27.4 inches) in height. The dry weight is around 147 kg (324 lbs), varying slightly by accessory configuration. Its compact form allows both transverse and longitudinal installation in front- or all-wheel-drive layouts. The lightweight aluminum construction reduces front axle load and contributes to balanced vehicle dynamics.
| Maintenance Data |
Recommended oil change interval is 10,000 km (6,000 miles). Spark plugs
are replaced every 100,000 km (62,000 miles). Air filter replacement
occurs every 20,000 km (12,000 miles). Coolant renewal is specified
every 160,000 km (100,000 miles). The serpentine drive belt should be
inspected every 40,000 km (25,000 miles) and replaced if worn or
cracked. The fuel filter should be replaced every 40,000 km (25,000
miles).
Compression pressure in each cylinder is approximately 1,300 kPa (190
psi) at 300 rpm, with a minimum allowable limit of 1,000 kPa (145 psi).
Maximum deviation between cylinders should not exceed 100 kPa (15 psi).
Idle speed is 700 ± 50 rpm. Valve clearance is automatically adjusted by
hydraulic lifters, eliminating the need for periodic valve lash checks.
The timing chain requires inspection only if abnormal noise or wear is
detected.
| Tightening Torques |
Cylinder head bolts: 40 Nm (30 lb-ft), then an additional 90°, followed
by another 90°.
Main bearing cap bolts: 60 Nm (44 lb-ft).
Connecting rod bolts: 40 Nm (30 lb-ft) plus 90°.
Camshaft bearing cap bolts: 10 Nm (7 lb-ft).
Crankshaft pulley bolt: 190 Nm (140 lb-ft).
Flywheel bolts: 85 Nm (63 lb-ft) plus 90°.
Spark plugs: 25 Nm (18 lb-ft).
Oil drain plug: 40 Nm (30 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).
Engine mount bolts: 60 Nm (44 lb-ft).
| Vehicle Applications |
The 4B12 engine has been widely used in various Mitsubishi and partner
models.
Notable applications include:
– Mitsubishi Outlander (CW and GF series, 2006–present)
– Mitsubishi Lancer and Lancer Sportback (CY series, 2007–2017)
– Mitsubishi Galant Fortis (2007–2015)
– Mitsubishi Delica D:5 (2007–present)
– Citroen C-Crosser and Peugeot 4007 (2007–2012, PSA collaboration)
– Jeep Compass and Patriot (under World Engine joint venture)
– Dodge Caliber and Chrysler Sebring (as 2.4 World Gasoline Engine)
The engine’s versatility allowed its adaptation for multiple platforms
and emission standards. Its balance of torque, efficiency, and low
vibration made it particularly suitable for urban crossovers and sedans
requiring smooth, refined power delivery.
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