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Mitsubishi 4G18 Specifications
| Engine Model: Mitsubishi 4G18 |
| Engine Type: 4-cycle inline 4-cylinder SOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 96.6 cu.in (1.58 L) |
| Rated Engine Power: 98-110 Hp (72-81 kW) at 6000 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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| General Technical Data |
The Mitsubishi 4G18 is a 1.6-liter inline-four gasoline engine developed by Mitsubishi Motors as part of the 4G1 engine series. Introduced in the late 1990s and continuing into the 2010s, the 4G18 was engineered for compact and mid-size passenger vehicles, offering a balance between performance, fuel economy, and reliability. With a displacement of 1,584 cc, it replaced smaller 1.5-liter units in several models while maintaining compact external dimensions and moderate weight.
The engine is a four-stroke, water-cooled,
inline-four configuration with a single overhead camshaft (SOHC)
operating sixteen valves via roller rocker arms and hydraulic lash
adjusters. Later versions incorporated Mitsubishi’s MIVEC (Mitsubishi
Innovative Valve timing Electronic Control) system on the intake side,
improving efficiency, torque delivery, and emissions compliance.
The 4G18 gained popularity in models such as the Mitsubishi Lancer,
Colt, and Proton Waja, providing dependable operation under a variety of
conditions. Known for its mechanical simplicity, strong aluminum head,
and cast-iron block, the engine became a workhorse for both domestic and
international markets. Its refinement and moderate output suited daily
drivers, offering good throttle response and service longevity when
maintained properly. The later MIVEC-equipped versions extended its
lifespan by meeting Euro 4 and Euro 5 emission standards while retaining
the same displacement and structural layout.
The Mitsubishi 4G18 has a displacement of 1,584 cc (96.6 cubic inches),
achieved by a bore of 76.0 mm (2.99 inches) and a stroke of 87.3 mm
(3.44 inches). This undersquare design favors low and mid-range torque
over high-revving characteristics, making the engine responsive in urban
driving. The compression ratio is typically 9.5:1 for non-MIVEC variants
and around 10.0:1 for MIVEC-equipped units, depending on market and
emission calibration.
The firing order is 1-3-4-2, and the crankshaft
rotates clockwise when viewed from the timing belt end. The block is
made of cast iron for rigidity and wear resistance, with five main
bearings supporting a forged steel crankshaft. The pistons are
lightweight aluminum alloy with full-floating pins and molybdenum-coated
skirts. Connecting rods are forged steel and precision-balanced for
smooth operation.
The aluminum alloy cylinder head features a single overhead camshaft
driven by a toothed rubber timing belt. The camshaft actuates sixteen
valves through roller rockers, reducing friction and valve train noise.
Hydraulic lash adjusters maintain zero valve clearance, eliminating
periodic adjustment. Early versions of the 4G18 used fixed valve timing,
while later versions employed MIVEC variable valve timing on the intake
camshaft, allowing adjustment of valve opening duration to enhance
low-end torque and high-end power simultaneously.
Maximum power output ranges from 98 to 110 Hp (72 to 81 kW, or 97 to 108
bhp) at around 6,000 revolutions per minute. Peak torque varies between
137 and 145 Nm (101 to 107 lb-ft) at approximately 4,500 rpm. The
redline is around 6,500 rpm. Idle speed is 750 ± 50 rpm.
The engine complies with Euro 3 to Euro 5 emission standards depending on configuration. The MIVEC-equipped variants feature improved mid-range torque and reduced fuel consumption due to variable intake valve timing adjustment of up to 30 degrees of crankshaft rotation.
| Fuel System |
The 4G18 uses an electronically controlled multi-point fuel injection (MPI) system. Fuel is supplied from an in-tank electric pump through a high-pressure line to the fuel rail, feeding four solenoid-actuated injectors mounted at the intake ports. The system operates at a fuel pressure of approximately 300 kPa (43 psi), maintained by a vacuum-referenced regulator.
A mass air flow (MAF) sensor and throttle position sensor provide input
to the engine control unit (ECU), which calculates injection pulse width
and timing. The injectors deliver finely atomized fuel for optimal
combustion, improving throttle response and fuel economy. Fuel cutoff
occurs during deceleration and at redline to prevent over-revving.
The throttle body is cable-operated in early engines and electronically
controlled (ETCS) in MIVEC versions. An idle air control (IAC) valve
regulates airflow during idling to stabilize speed under varying
electrical loads. The recommended fuel is unleaded gasoline with a
minimum octane rating of 95 RON (approximately 91 AKI). Fuel filter
replacement is suggested every 40,000 km (25,000 miles) for proper fuel
delivery. Fuel injectors should be cleaned or inspected at 80,000 km
(50,000 miles).
| Lubrication System |
The 4G18 employs a full-pressure wet-sump lubrication system using a trochoid-type oil pump driven by the crankshaft. Oil is drawn from the sump through a strainer and delivered under pressure to the main oil gallery, lubricating crankshaft bearings, connecting rods, camshaft journals, and valve train components.
A full-flow spin-on paper-element oil filter is located on the engine
block for easy replacement. Oil pressure at idle is approximately 100
kPa (15 psi), rising to around 400 kPa (58 psi) at 3,000 rpm. Total oil
capacity including the filter is 3.3 liters (3.5 US quarts, 2.9 Imperial
quarts).
Recommended engine oil viscosity is SAE 5W-30 or 10W-30 meeting API SJ
or higher standards. The crankcase ventilation system employs a positive
crankcase ventilation (PCV) valve integrated into the rocker cover,
ensuring removal of blow-by gases and maintaining internal pressure
balance.
Oil and filter changes are advised every 10,000 km (6,000 miles) under normal conditions, or every 5,000 km (3,000 miles) for severe service. The MIVEC-equipped version benefits from higher-grade synthetic oil to ensure proper operation of the hydraulic cam phaser.
| Cooling System |
The cooling system is a pressurized, liquid-cooled design utilizing a
belt-driven centrifugal water pump. Coolant circulates through the
engine block, cylinder head, radiator, and heater core, ensuring even
heat dissipation. The thermostat begins to open at 82 C (180°F) and is
fully open at approximately 95°C (203°F). The radiator is aluminum with
plastic end tanks, and cooling is assisted by an electric fan controlled
by the ECU. Total coolant capacity is approximately 5.8 liters (6.1 US
quarts, 5.1 Imperial quarts).
The system operates at a pressure of around 88 kPa (13 psi), maintained
by the radiator cap. Coolant should be replaced every two years or
40,000 km (25,000 miles). A 50/50 mixture of ethylene glycol antifreeze
and distilled water provides corrosion protection and freeze resistance
down to –35°C (–31°F). Temperature sensors monitor coolant temperature
for engine management and dashboard indication. Overheating protection
is provided through a fail-safe ECU mode that limits engine power if
excessive temperature is detected.
| Intake and Exhaust Systems |
The induction system consists of a plastic intake manifold with long runners designed to optimize air velocity and mid-range torque. The air cleaner assembly contains a dry paper element filter, replaceable every 20,000 km (12,000 miles). A resonator chamber reduces intake noise.
The throttle body diameter is 50 mm (1.97 inches) for standard models
and slightly larger in MIVEC-equipped versions to enhance airflow. The
exhaust manifold is cast iron in early engines and stainless steel in
later ones, connecting to a catalytic converter located near the
manifold to enable quick light-off and reduced emissions.
The exhaust gas recirculation (EGR) system is used in
emission-controlled versions to reduce NOx formation by recirculating a
portion of exhaust gases into the intake. Oxygen sensors are placed
upstream and downstream of the catalytic converter for closed-loop
mixture control. Some later MIVEC variants included secondary air
injection during cold starts to speed up catalytic converter warm-up.
| Ignition and Electrical System |
Ignition is electronically controlled and distributorless, employing a waste-spark ignition coil system on early engines and a coil-on-plug setup on later MIVEC variants. The ECU precisely manages spark timing based on inputs from the crankshaft position sensor, camshaft sensor, knock sensor, and throttle position sensor. Spark plugs are typically NGK BKR6E-11 or equivalent, gapped at 1.1 mm (0.043 inches).
Replacement is recommended every 30,000 to 40,000 km (18,000 to 25,000 miles). The electrical system includes a 12-volt alternator rated at 80 to 90 amperes and a 1.2-kilowatt reduction-gear starter motor. Ground connections between engine and chassis are reinforced with braided straps to ensure consistent conductivity.
| Valve Timing and Drive Mechanism |
The 4G18 uses a toothed rubber timing belt to drive the camshaft and water pump. The belt tension is maintained automatically by a spring-loaded or hydraulic tensioner. Replacement of the timing belt, tensioner, and idler pulleys is recommended every 100,000 km (60,000 miles).
In MIVEC-equipped versions, the intake camshaft features a hydraulically controlled phaser operated by oil pressure, varying valve timing for improved torque and efficiency across the rev range. The valve cover includes integrated oil passages for the MIVEC actuator, requiring clean oil and regular filter maintenance for reliable function.
| Dimensions and Weight |
Overall engine length is approximately 635 mm (25.0 inches), width 610 mm (24.0 inches), and height 690 mm (27.2 inches). The dry weight is about 115 kg (254 lbs) for non-MIVEC versions and around 120 kg (265 lbs) for MIVEC-equipped variants. The compact design allows both transverse and longitudinal mounting depending on the vehicle. Engine mounting employs three or four rubber-isolated brackets to minimize vibration transmission to the chassis, contributing to low NVH characteristics.
| Maintenance Data |
Routine maintenance ensures reliability and longevity. Engine oil and filter replacement should occur every 10,000 km (6,000 miles). Air filter every 20,000 km (12,000 miles). Spark plug replacement every 40,000 km (25,000 miles). Timing belt and water pump every 100,000 km (60,000 miles). Coolant replacement every 40,000 km (25,000 miles) or two years.
Valve train requires no clearance adjustment due to hydraulic lash adjusters. Idle speed is 750 ± 50 rpm. Standard compression pressure is 1,200 kPa (174 psi) per cylinder with a minimum of 980 kPa (142 psi) and a maximum deviation between cylinders not exceeding 100 kPa (15 psi).
| Tightening Torques |
Cylinder head bolts: tighten in sequence to 29 Nm (21 lb-ft), then 59 Nm
(44 lb-ft), then an additional 90 degrees.
Main bearing cap bolts: 65 Nm (48 lb-ft).
Connecting rod bolts: 40 Nm (30 lb-ft) plus 90 degrees.
Camshaft bearing cap bolts: 12 Nm (9 lb-ft).
Crankshaft pulley bolt: 180 Nm (133 lb-ft).
Flywheel bolts: 85 Nm (63 lb-ft).
Spark plugs: 18 Nm (13 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).
| Vehicle Applications |
The Mitsubishi 4G18 engine was widely used across several global markets
and joint-venture vehicles.
Primary applications include:
– Mitsubishi Lancer (CS, CK, and CY series, 2000–2010)
– Mitsubishi Colt Plus and Mirage (select markets)
– Proton Waja 1.6 (Malaysia, 2000s)
– Proton Gen-2 (1.6 variant)
– Mitsubishi Space Star and Lancer Cedia Wagon
– Chinese-assembled models by Soueast and BYD under license
The engine’s versatility, simplicity, and parts availability made it a
global power unit, appreciated for its balance of smoothness and
economy. With regular maintenance, service life often exceeds 300,000 km
(186,000 miles).
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