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Mitsubishi 4G63 Specifications
| Engine Model: Mitsubishi 4G63 |
| Engine Type: 4-cycle inline 4-cylinder SOHC or DOHC liquid-cooled gasoline |
| Total Displacement: 121.9 cu.in (1.99 L) |
| Rated Engine Power: 100-140 Hp (74-104 kW) at 6000 rpm |
| Fuel System Type: Carburetor or multi-point electronic fuel injection |
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| General Technical Data |
The Mitsubishi 4G63 is a 2.0-liter inline four-cylinder gasoline engine belonging to the long-running Sirius engine family, developed by Mitsubishi Motors. Introduced in the early 1980s and produced for over two decades, it became one of the most well-known engines in the company’s lineup. While it is most famous for its turbocharged versions powering high-performance models such as the Lancer Evolution, the naturally aspirated 4G63 variant served in a wide range of passenger vehicles where reliability, smooth operation, and moderate power output were prioritized.
It featured a robust cast-iron cylinder block
combined with an aluminum cylinder head, a dual overhead camshaft
configuration, and a 16-valve layout that provided good breathing
efficiency. This version emphasized balance between performance and
economy, making it suitable for sedans and coupes across both domestic
and export markets.
The naturally aspirated 4G63 was produced in both single overhead cam
(SOHC) and double overhead cam (DOHC) configurations, depending on model
and market. Its balanced reciprocating assembly, square geometry, and
conservative tuning ensured long-term durability and quiet operation.
Owing to its mechanical simplicity, it became a favorite among tuners,
mechanics, and daily drivers alike. The 4G63’s refinement and
flexibility helped establish Mitsubishi’s engineering reputation
throughout the 1980s and 1990s.
The Mitsubishi 4G63 has a total displacement of 1,997 cc (121.9 cubic
inches), achieved through a bore of 85.0 mm (3.35 inches) and a stroke
of 88.0 mm (3.46 inches). The engine’s compression ratio varies
depending on version, typically between 9.0:1 and 9.5:1 for naturally
aspirated models. The block is cast iron for superior rigidity and
thermal stability, while the cylinder head is aluminum alloy to improve
heat dissipation and reduce overall weight.
The crankshaft is forged steel and supported by
five main bearings for smooth operation and strength. The connecting
rods are forged steel and the pistons are lightweight aluminum alloy
with full-floating pins. The firing order is 1-3-4-2, and the crankshaft
rotates clockwise when viewed from the timing belt side.
In its naturally aspirated form, the 4G63 produces between 100 and 140
horsepower (74 to 104 kW, 101 to 142 bhp) at approximately 6,000
revolutions per minute, and torque output ranges between 160 and 180 Nm
(118 to 133 lb-ft) at 4,500 rpm. The redline is around 6,500 rpm with
fuel cut-off near 6,800 rpm. Idle speed is typically set at 750 ± 50
rpm.
Early versions employed belt-driven single overhead camshafts, while later and more advanced models used a dual overhead camshaft (DOHC) configuration operating four valves per cylinder for a total of sixteen valves. Valve clearance adjustment is accomplished using mechanical lifters with shims on earlier models, while later units feature hydraulic lash adjusters to eliminate the need for periodic adjustment.
| Fuel System |
The naturally aspirated 4G63 was produced with both carbureted and electronically fuel-injected (EFI) systems. Early SOHC variants utilized twin-barrel carburetors providing simplicity and ease of service. Later versions adopted electronic multi-point fuel injection, improving throttle response, fuel economy, and emissions compliance.
The EFI system employs an electric fuel pump located in the fuel tank,
feeding a pressurized fuel rail that supplies the injectors. Typical
fuel pressure is maintained at approximately 300 kPa (43 psi). The
injectors are solenoid-actuated, delivering finely atomized fuel
directly to the intake ports. Excess fuel returns to the tank via a
pressure-regulated return line.
Fuel metering is controlled by an electronic control unit (ECU) based on
input from the throttle position sensor, manifold absolute pressure
sensor, engine speed signal, and oxygen sensor. The recommended fuel
grade is unleaded gasoline with an octane rating of at least 91 RON (87
AKI) for carbureted engines and 95 RON (91 AKI) for EFI models. The air
intake system incorporates a dry paper air filter element and an
acoustic resonator to minimize induction noise. Air filter service
interval is every 20,000 km (12,000 miles).
| Lubrication System |
The lubrication system of the 4G63 is a full-pressure wet-sump type with a trochoid oil pump driven by the crankshaft. The system draws oil from the sump through a strainer, sending it through a full-flow oil filter before distributing it via internal galleries to crankshaft bearings, connecting rod journals, camshafts, and valve train components.
Oil pressure at idle is approximately 100 kPa (15 psi), rising to about
400 kPa (58 psi) at 3,000 rpm. Piston oil squirters are used in certain
versions to reduce piston crown temperatures and prevent detonation. The
total oil capacity with filter replacement is 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.
The crankcase ventilation system includes a positive crankcase
ventilation (PCV) valve to route blow-by gases back into the intake for
combustion, reducing emissions. Oil and filter should be replaced every
10,000 km (6,000 miles) under normal service and every 5,000 km (3,000
miles) under severe driving conditions.
| Cooling System |
The 4G63 uses a liquid-cooled, pressurized system with a belt-driven centrifugal water pump. Coolant circulates through the block, cylinder head, radiator, and heater core. The thermostat begins to open at approximately 82 C (180°F) and is fully open at around 95°C (203°F). Coolant capacity is 6.7 liters (7.1 US quarts, 5.9 Imperial quarts). The system is designed to maintain optimal thermal balance under varying load and ambient conditions.
The radiator is of the cross-flow aluminum type with a plastic header tank, while engine cooling fans may be belt-driven or electric depending on vehicle configuration. Recommended coolant mixture is 50% ethylene glycol antifreeze and 50% distilled water, providing freeze protection down to –35°C (–31°F). Coolant replacement is recommended every two years or 40,000 km (25,000 miles).
| Intake and Exhaust Systems |
The intake manifold is made of cast aluminum alloy, tuned for mid-range torque and even distribution to all cylinders. Later engines use plastic composite manifolds to reduce weight and heat soak. The throttle body is cable-operated, typically measuring 60 mm (2.36 inches) in diameter.
The exhaust manifold is cast iron on most versions, with smooth internal runners leading to a dual-branch outlet. Exhaust gas recirculation (EGR) is employed in most variants to reduce nitrogen oxide emissions. The exhaust system includes a catalytic converter and oxygen sensor for feedback control in EFI-equipped models.
| Ignition and Electrical System |
The ignition system of the naturally aspirated 4G63 differs by generation. Early versions use a mechanical distributor with vacuum and centrifugal advance, while later units feature electronic ignition with an integrated igniter and coil pack controlled by the ECU. The ignition timing at idle is typically set around 5 to 10 degrees before top dead center (BTDC).
Spark plug specification is NGK BPR6ES or equivalent, gapped at 1.1 mm (0.043 inch). The alternator output ranges between 70 and 90 amperes, and the starter motor is a 1.2-kilowatt reduction gear type. The electrical system operates at 12 volts DC, with negative ground. Battery capacity is typically between 45 and 60 ampere-hours (Ah).
| Valve Timing and Drive Mechanism |
The camshaft(s) of the 4G63 are driven by a toothed rubber timing belt. The belt also drives the water pump and balance shafts in versions equipped with Mitsubishi’s silent shaft system, which minimizes secondary vibration inherent in inline-four engines. Timing belt replacement interval is every 100,000 km (60,000 miles), including tensioner and idler pulleys.
Valve timing for the DOHC variant is as follows: intake opens 5° BTDC and closes 47° ABDC, while exhaust opens 51° BBDC and closes 5° ATDC. SOHC engines have similar though slightly reduced timing overlap to improve idle stability and emissions.
| Dimensions and Weight |
The complete engine assembly measures approximately 670 mm (26.4 inches) in length, 620 mm (24.4 inches) in width, and 680 mm (26.8 inches) in height. The dry weight is around 155 kg (342 lbs) for SOHC variants and approximately 160 kg (353 lbs) for DOHC units. Engine mounts are positioned to minimize vibration transfer and maintain good weight distribution within the chassis. The compact yet durable design makes it suitable for both longitudinal and transverse installations.
| Maintenance Data |
Routine maintenance is critical to ensure long-term reliability. Engine oil and filter should be replaced every 10,000 km (6,000 miles). Spark plugs are replaced every 30,000 to 40,000 km (18,000 to 25,000 miles), depending on driving conditions. The air filter element is replaced every 20,000 km (12,000 miles). Valve clearance inspection, if equipped with mechanical lifters, is performed every 80,000 km (50,000 miles).
The timing belt and tensioner should be replaced every 100,000 km (60,000 miles). Coolant replacement interval is 40,000 km (25,000 miles) or two years. Compression pressure should be approximately 1,300 kPa (190 psi) with a minimum of 1,000 kPa (145 psi). Idle speed is 750 ± 50 rpm. Valve cover gasket, PCV valve, and fuel filter should be inspected at every major service interval.
| Tightening Torques |
Cylinder head bolts: first stage 29 Nm (21 lb-ft), second stage 59 Nm
(44 lb-ft), final angle tightening 90 degrees.
Main bearing cap bolts: 83 Nm (61 lb-ft).
Connecting rod bolts: 43 Nm (32 lb-ft) plus 90 degrees.
Camshaft bearing cap bolts: 13 Nm (10 lb-ft).
Flywheel bolts: 83 Nm (61 lb-ft) plus 90 degrees.
Crankshaft pulley bolt: 180 Nm (133 lb-ft).
Oil pump cover bolts: 9 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).
Spark plugs: 18 Nm (13 lb-ft).
Drain plug: 40 Nm (30 lb-ft).
| Vehicle Applications |
The Mitsubishi 4G63 naturally aspirated engine appeared in a wide
variety of vehicles produced from the early 1980s through the 2000s.
Notable applications include:
– Mitsubishi Galant (E30, E50, E70, E90 series)
– Mitsubishi Lancer and Mirage (E30–E50 platforms)
– Mitsubishi Eclipse and Eagle Talon (base models, non-turbo)
– Mitsubishi Delica and Space Wagon (select trims)
– Hyundai Sonata and Stellar (under license)
– Proton Wira and Perdana (licensed production versions)
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