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Mitsubishi 4G64 Specifications
| Engine Model: Mitsubishi 4G64 |
| Engine Type: 4-cycle inline 4-cylinder SOHC or DOHC liquid-cooled gasoline |
| Total Displacement: 143.4 cu.in (2.35 L) |
| Rated Engine Power: 110-160 Hp (81-118 kW) at 5500 rpm |
| Fuel System Type: Multi-point fuel injection or gasoline direct injection |
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| General Technical Data |
The Mitsubishi 4G64 engine is a 2.4-liter inline-four gasoline powerplant belonging to the Sirius family of engines that served as one of Mitsubishi’s most versatile and long-lived designs. Produced from the late 1980s through the 2000s, the 4G64 was employed in a wide variety of vehicles ranging from compact sedans to light commercial trucks and SUVs. It was developed as the large-displacement derivative of the 4G63, sharing much of its architecture but featuring a longer stroke to provide greater torque and smoother low-end response.
Throughout its production life, it evolved
through several distinct configurations, including the early SOHC
carbureted and multi-point fuel injected versions, the later DOHC/MIVEC
high-performance variant, and the advanced GDI (Gasoline Direct
Injection) system that focused on efficiency and emissions reduction.
The 4G64 became renowned for its reliability, mechanical simplicity, and
adaptability to diverse applications.
The Mitsubishi 4G64 has a displacement of 2,351 cc (143.4 cubic inches),
achieved through a bore of 86.5 mm (3.41 inches) and a stroke of 100.0
mm (3.94 inches). This long-stroke design enhances torque delivery at
low and mid engine speeds, a key advantage for utility vehicles and
SUVs. The compression ratio varies by configuration: approximately 9.0:1
for the SOHC MPI version, 10.0:1 for the DOHC/MIVEC, and up to 11.0:1
for the GDI version.
The cylinder block is constructed from cast
iron for durability, while the cylinder head is made of aluminum alloy
to reduce weight and improve thermal dissipation. The engine uses five
main bearings to support the forged steel crankshaft, with full-floating
piston pins and aluminum alloy pistons equipped with molybdenum-coated
skirts to reduce friction.
The firing order is 1-3-4-2, and the crankshaft rotates clockwise viewed
from the flywheel end. Each cylinder uses two valves per cylinder on
SOHC models and four valves per cylinder on DOHC and MIVEC versions. The
SOHC configuration uses rocker arms with hydraulic lash adjusters,
eliminating the need for periodic valve clearance adjustment.
The DOHC versions employ direct-acting bucket
tappets with shim adjustment for precise valve control. MIVEC
(Mitsubishi Innovative Valve timing Electronic Control) allows variable
timing and lift on the intake valves, optimizing torque at low speed and
power at high speed. The timing belt drives both the camshaft(s) and the
water pump, with a replacement interval of 100,000 km (60,000 miles).
Power output depends on version and market. The SOHC multi-point
injected variant typically produces 110 to 125 Hp (81 to 92 kW, 108 to
123 bhp) at 5,500 rpm, with torque in the range of 190 to 210 Nm (140 to
155 lb-ft) at around 3,000 rpm. The DOHC/MIVEC version, found in
performance applications such as the Galant and Eclipse, generates up to
160 horsepower (118 kW, 158 bhp) and 220 Nm (162 lb-ft) of torque.
The 4G64 GDI, utilizing high-compression direct injection, achieves around 150 horsepower (110 kW, 148 bhp) and 225 Nm (166 lb-ft) while maintaining superior fuel economy and reduced emissions. Redline varies between 6,000 and 6,800 rpm depending on configuration.
| Fuel System |
The 4G64 employs different fuel systems according to version. The standard MPI (Multi-Point Injection) type uses a low-pressure electric fuel pump located inside the fuel tank to deliver fuel through a filter and rail to four solenoid-controlled injectors positioned in the intake ports. Fuel pressure is regulated to approximately 300 kPa (43 psi) via a vacuum-referenced pressure regulator.
Fuel injection timing and duration are controlled by the ECU based on
sensor inputs such as throttle position, manifold pressure, air
temperature, and oxygen feedback. The fuel used is unleaded gasoline of
at least 91 RON (87 AKI).
The GDI version, introduced in the late 1990s, employs a high-pressure
direct injection system. A low-pressure pump sends fuel to a mechanical
high-pressure pump mounted on the cylinder head, which compresses the
fuel to approximately 8 to 12 Mpa (1,160 to 1,740 psi). Special
multi-hole injectors spray fuel directly into the combustion chambers,
enabling lean-burn operation under light loads and homogeneous mixture
at higher loads.
The GDI ECU finely controls injection timing to create a stratified charge near the spark plug during idle and cruise conditions. This results in improved fuel economy and reduced CO2 emissions compared to conventional MPI systems. Periodic injector cleaning and high-quality fuel are essential for maintaining proper operation of the GDI system.
| Lubrication System |
The lubrication system is a fully pressurized wet-sump type employing a trochoid-type oil pump driven directly by the crankshaft. Oil is drawn from the sump through a strainer and sent through the full-flow spin-on filter before being distributed to the crankshaft bearings, connecting rods, camshaft journals, and valve gear. Oil jets under the pistons spray lubricant for cooling, particularly important for high-output DOHC/MIVEC and GDI variants.
Normal oil pressure at 3,000 rpm is approximately 400 to 500 kPa (58 to 73 psi), and at idle it is about 100 kPa (15 psi). Total oil capacity with filter replacement is approximately 4.3 liters (4.5 US quarts, 3.8 Imperial quarts). Recommended oil viscosity is SAE 5W-30 or 10W-30 meeting API SJ or higher standards. Regular oil and filter changes are advised every 10,000 km (6,000 miles) under normal conditions or every 5,000 km (3,000 miles) under severe conditions.
| Cooling System |
The 4G64 uses a liquid-cooling system with a belt-driven centrifugal water pump circulating coolant through the block, head, radiator, and heater core. The thermostat begins to open at 82°C (180°F) and is fully open at about 95°C (203°F). A cross-flow aluminum radiator with an electric fan or viscous clutch fan (depending on application) maintains optimal engine temperature. System pressure is maintained by a radiator cap rated at approximately 88 kPa (13 psi).
Total coolant capacity is about 7.0 liters (7.4 US quarts, 6.2 Imperial quarts). Recommended coolant is a 50/50 mix of ethylene glycol and distilled water, providing freeze protection down to –35°C (–31°F). Coolant replacement interval is every 40,000 km (25,000 miles) or two years. The system includes sensors for ECU temperature input and dashboard gauge indication.
| Intake and Exhaust Systems |
The intake system varies with engine type. Early SOHC engines employ an
aluminum intake manifold with long runners designed to improve low-end
torque, while the DOHC/MIVEC and GDI versions use tuned composite
manifolds with shorter runners for better high-speed breathing. The
throttle is cable-actuated on early engines and electronically
controlled on later models, especially those equipped with GDI. The air
filter element is a replaceable dry paper type, to be renewed every
20,000 km (12,000 miles).
The exhaust manifold is cast iron or stainless steel depending on model
and feeds into a close-coupled catalytic converter. The system
incorporates one or more oxygen sensors to manage closed-loop fuel
control. GDI engines employ a more complex exhaust gas recirculation
(EGR) and secondary air injection system to reduce NOx emissions. Proper
function of these systems is vital for maintaining compliance with
emission standards.
| Ignition and Electrical System |
The ignition system evolved over the 4G64’s lifespan. Early models used a distributor-type ignition with a single coil and mechanical advance, while later MPI and DOHC variants adopted electronic ignition with crank angle sensors and waste-spark dual-coil setups. GDI versions employ coil-on-plug ignition with full electronic control.
Spark plug type is NGK BKR6E or iridium equivalent, gapped to 1.1 mm (0.043 inch). Replacement interval is 30,000 to 40,000 km (18,000 to 25,000 miles) for standard plugs and up to 100,000 km (62,000 miles) for iridium types. The alternator rating varies from 80 to 100 amperes, and the starter motor is a 1.2 kilowatt gear-reduction unit. Electrical system voltage is 12V DC.
| Emission Control and Other Systems |
The 4G64 complies with various emission regulations depending on market. The PCV (positive crankcase ventilation) system routes blow-by gases to the intake manifold. The EGR valve recirculates a portion of exhaust gases into the intake to reduce NOx formation. Later models include an EVAP (evaporative emission control) system with a charcoal canister and purge solenoid.
The GDI version adds additional components for vapor management and advanced catalytic monitoring through OBD-II. Idle air control is electronically regulated via a stepper motor or throttle actuator. In MIVEC engines, the ECU coordinates variable valve timing with load and speed to optimize both performance and emissions.
| Dimensions and Weight |
The 4G64 engine assembly measures approximately 660 mm (26.0 inches) in length, 630 mm (24.8 inches) in width, and 690 mm (27.2 inches) in height. The dry weight ranges from 150 kg (331 lbs) for the basic SOHC version to about 160 kg (353 lbs) for DOHC/MIVEC and GDI configurations. Engine mounts are rubber-isolated to minimize vibration and noise transfer to the chassis. The engine’s compact yet robust design allows longitudinal or transverse installation depending on application.
| Maintenance Data |
Regular maintenance ensures the long life typical of Mitsubishi’s Sirius engines. Oil and filter should be replaced every 10,000 km (6,000 miles), with air filter every 20,000 km (12,000 miles). Fuel filter replacement is recommended every 40,000 km (25,000 miles). Spark plug inspection occurs every 30,000 km (18,000 miles) and replacement at 60,000 km (37,000 miles) unless using extended-life plugs.
The timing belt, balance shaft belt, and tensioner are replaced at
100,000 km (60,000 miles), along with the water pump. Coolant is renewed
every two years or 40,000 km (25,000 miles). Valve clearances on DOHC
versions should be checked every 80,000 km (50,000 miles).
Compression pressure for a healthy engine is approximately 1,200 kPa
(174 psi) with a minimum allowable limit of 1,000 kPa (145 psi). Maximum
variation between cylinders should not exceed 100 kPa (15 psi). Normal
idle speed is 700 ± 50 rpm for MPI and 750 ± 50 rpm for GDI. Ignition
timing at idle (MPI version) is approximately 10 degrees BTDC. Engine
oil pressure warning lamp should extinguish within two seconds of
start-up under normal conditions.
| Tightening Torques |
Cylinder head bolts: 1st stage 30 Nm (22 lb-ft), 2nd stage 60 Nm (44
lb-ft), plus 90 deg angle tightening.
Main bearing cap bolts: 70 Nm (52 lb-ft).
Connecting rod bolts: 40 Nm (30 lb-ft) plus 90 degrees.
Camshaft bearing cap bolts: 10 Nm (7 lb-ft).
Crankshaft pulley bolt: 180 Nm (133 lb-ft).
Flywheel bolts: 85 Nm (63 lb-ft) plus 90 degrees.
Intake manifold bolts: 25 Nm (18 lb-ft).
Exhaust manifold nuts: 35 Nm (26 lb-ft).
Oil pan bolts: 9 Nm (7 lb-ft).
Spark plugs: 25 Nm (18 lb-ft).
Drain plug: 40 Nm (30 lb-ft).
| Vehicle Applications |
The 4G64 engine was widely used across Mitsubishi’s global lineup.
Key applications include:
– Mitsubishi Galant (1988–2006, various markets)
– Mitsubishi Eclipse (1990–2005, including GS and RS trims)
– Mitsubishi Outlander (early models)
– Mitsubishi Pajero/Montero (base versions)
– Mitsubishi L200/Delica (light truck and van applications)
– Mitsubishi Space Wagon/Chariot
– Proton Waja and certain Hyundai and Chrysler vehicles under licensing
agreements
The engine’s adaptable design made it suitable for both longitudinal and
transverse installations. In North America, it powered several
Chrysler-built models such as the Dodge Stratus and Plymouth Voyager.
The GDI version saw extensive use in Japanese domestic models
emphasizing fuel efficiency.
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