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Mitsubishi 4G15 Specifications
| Engine Model: Mitsubishi 4G15 |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve or 16-valve liquid-cooled gasoline |
| Total Displacement: 89.6 cu.in (1.46 L) |
| Rated Engine Power: 70-110 Hp (51-81 kW) at 5800 rpm |
| Fuel System Type: Carburetor or electronic fuel injection |
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| General Technical Data |
The Mitsubishi 4G15 is a 1.5-liter inline-four, four-stroke, water-cooled gasoline engine that belongs to Mitsubishi’s long-running Orion engine family. Introduced in the early 1980s, the 4G15 powered a wide variety of small and compact Mitsubishi vehicles, including the Mirage, Colt, and Lancer. It was designed for economy, reliability, and ease of maintenance, evolving over time from simple carbureted versions to more advanced electronic fuel injection (EFI) and multi-point injection (MPI) variants.
With its durable cast-iron block and aluminum
alloy cylinder head, the engine achieved an excellent balance of
performance, longevity, and affordability. The 4G15 became one of
Mitsubishi’s most widely produced small engines, remaining in production
for more than two decades.
The early versions employed a SOHC (single overhead camshaft) 8-valve
layout with carburetion, producing modest output suitable for urban use.
Later EFI and MPI versions introduced in the 1990s added improved
combustion efficiency, higher compression, and cleaner emissions, while
some models adopted a 16-valve configuration.
The final iterations featured the use of
Mitsubishi’s MIVEC variable valve timing system in selected markets,
achieving higher output and better fuel economy. Across its production
span, the 4G15 established itself as a reliable and serviceable
powerplant found in millions of vehicles worldwide.
The Mitsubishi 4G15 engine has a total displacement of 1,468 cc (89.6
cubic inches), achieved through a bore of 75.5 mm (2.97 inches) and a
stroke of 82.0 mm (3.23 inches). The engine operates on the Otto cycle
with a compression ratio ranging between 9.0:1 for carbureted units and
up to 10.0:1 for later EFI/MPI versions. The firing order is 1-3-4-2,
and the crankshaft rotates clockwise when viewed from the flywheel side.
The inline-four layout provides compact dimensions and simple
maintenance accessibility.
The cylinder block is made of cast iron, ensuring rigidity and wear
resistance, while the cylinder head is aluminum alloy for improved heat
dissipation. The crankshaft is supported by five main bearings, and the
connecting rods are forged steel. Pistons are aluminum alloy, fitted
with two compression rings and one oil control ring.
Valve configuration varies by generation: early
8-valve SOHC engines used rocker arms and mechanical tappets, while
later 16-valve versions featured lighter cam followers and hydraulic
lash adjusters. Camshaft drive is by toothed rubber timing belt, which
also drives the water pump.
In its base carbureted form, the 4G15 produced between 70 and 80 Hp
(51–59 kW, 69–79 bhp) at approximately 5,500 rpm and torque of about 115
to 120 Nm (85–89 lb-ft) at 3,000–3,500 rpm. The later EFI and MPI
12-valve and 16-valve versions delivered between 88 and 110 Hp (65–81
kW, 87–108 bhp) at 6,000 rpm with torque between 130 and 145 Nm (96–107
lb-ft) at around 4,000 rpm. The redline is typically 6,500 rpm, and idle
speed is 750 ± 50 rpm.
| Fuel System |
Early 4G15 engines utilized a single or twin-barrel downdraft carburetor
with mechanical and vacuum controls. These carbureted systems employed
an electric choke and mechanical fuel pump driven by the camshaft. Fuel
delivery was relatively simple, relying on manifold vacuum and jet
calibration. The fuel used is unleaded gasoline with an octane rating of
at least 91 RON (87 AKI).
Later electronic fuel injection (EFI) and multi-point injection (MPI)
systems were introduced in the 1990s. These systems replaced the
carburetor with electronically controlled injectors mounted in the
intake manifold. An electric in-tank fuel pump supplied fuel at
approximately 300 kPa (43 psi). The fuel pressure regulator maintained
constant differential pressure relative to manifold vacuum.
An electronic control unit (ECU) governed injection timing and pulse
width using data from sensors including throttle position, intake air
temperature, manifold absolute pressure (MAP), oxygen, and coolant
temperature sensors. MPI versions provided better fuel atomization,
reduced emissions, and improved cold-start performance.
The air intake system employs a dry paper filter element housed in a
plastic airbox. Filter replacement is recommended every 20,000 km
(12,000 miles). The exhaust system features a cast-iron manifold leading
to a catalytic converter in EFI-equipped models, while carbureted
versions often used simpler exhaust piping with minimal emissions
control.
| Lubrication System |
The 4G15 uses a full-pressure lubrication system with a trochoid-type oil pump driven by the crankshaft. Oil is drawn through a strainer from the sump and delivered under pressure to the main gallery, feeding crankshaft bearings, connecting rod bearings, camshaft journals, and valve train components.
A full-flow spin-on oil filter is mounted on the block’s side. Normal
oil pressure is approximately 400 kPa (58 psi) at 3,000 rpm and 100 kPa
(15 psi) at idle. The oil capacity, including filter change, is 3.5
liters (3.7 US quarts, 3.1 Imperial quarts). Recommended oil is SAE
5W-30 or 10W-30 meeting API SJ or higher.
The positive crankcase ventilation (PCV) system routes blow-by gases
from the crankcase to the intake manifold to reduce emissions and
maintain internal pressure balance. Regular oil and filter changes every
10,000 km (6,000 miles) are essential for long-term reliability. Severe
driving conditions may require shorter intervals of 5,000 km (3,000
miles).
| Cooling System |
The cooling system is liquid-cooled with a belt-driven centrifugal water pump circulating coolant through the cylinder block, head, and radiator. The thermostat begins to open at approximately 82°C (180°F) and is fully open near 95°C (203°F). A pressurized radiator cap maintains system pressure around 88 kPa (13 psi).
The radiator is aluminum core with plastic tanks, cooled by a belt-driven or electric fan depending on the vehicle model. The total coolant capacity is about 5.5 liters (5.8 US quarts, 4.8 Imperial quarts). A 50/50 mixture of ethylene glycol antifreeze and water is recommended for freeze protection to –35°C (–31°F). Coolant replacement is advised every 40,000 km (25,000 miles) or two years.
| Intake and Exhaust Systems |
The induction system of the early 4G15 utilized a cast aluminum intake manifold tuned for low-end torque, while later EFI/MPI versions adopted a longer-runner plastic or aluminum design for midrange efficiency. The throttle body diameter varies between 45 and 50 mm depending on model year and configuration.
The air cleaner assembly includes an intake resonator to reduce noise. The exhaust manifold in later engines was designed with smoother runners and an integrated catalytic converter for better emissions performance. Exhaust gas recirculation (EGR) was introduced in EFI versions to reduce nitrogen oxide emissions.
| Ignition and Electrical System |
The ignition system in carbureted engines employed a conventional distributor with mechanical and vacuum advance. The distributor was driven by the camshaft and used an external ignition coil. Later EFI and MPI engines transitioned to electronic ignition systems with integrated igniters and crank angle sensors for precise spark timing.
Some models adopted distributorless ignition (DIS) with dual coil packs. Spark plugs are typically NGK BPR6ES or Denso equivalents, gapped at 1.1 mm (0.043 inch). Spark plug replacement is recommended every 30,000 km (18,000 miles). The alternator output ranges from 65 to 90 amperes, and the starter motor is a 1.0 to 1.2 kilowatt reduction type.
| Valve Timing and Drive Mechanism |
The camshaft is belt-driven from the crankshaft via a reinforced rubber timing belt. Belt replacement interval is 90,000 to 100,000 km (56,000–62,000 miles). The timing belt also drives the water pump. Proper alignment of timing marks on crankshaft and camshaft pulleys is critical for correct valve timing. Valve clearance on mechanical lifter models is set to 0.20 mm (0.008 inch) for intake and 0.25 mm (0.010 inch) for exhaust when cold. Hydraulic lifter versions require no periodic adjustment.
| Dimensions and Weight |
The overall length of the 4G15 engine is approximately 640 mm (25.2 inches), width 580 mm (22.8 inches), and height 680 mm (26.8 inches). The dry weight is around 115 kg (254 lbs) for carbureted models and about 125 kg (276 lbs) for EFI-equipped variants. Compact dimensions allow both transverse and longitudinal installation, depending on vehicle layout. Engine mounts use rubber isolators to minimize vibration and noise transfer to the chassis.
| Maintenance Data |
Regular maintenance ensures reliable performance and long service life. Recommended service intervals are as follows: engine oil and filter every 10,000 km (6,000 miles); air filter every 20,000 km (12,000 miles); spark plugs every 30,000 km (18,000 miles); timing belt and water pump every 100,000 km (62,000 miles); and coolant every two years.
Valve clearance (if applicable) should be checked every 60,000 km
(37,000 miles). Fuel filters are replaced every 40,000 km (25,000 miles)
in carbureted versions and every 80,000 km (50,000 miles) in EFI
versions.
Normal cylinder compression pressure is 1,300 kPa (190 psi) with a
minimum allowable of 1,000 kPa (145 psi). Compression difference between
cylinders should not exceed 100 kPa (15 psi). Idle speed is 750 ± 50
rpm. Ignition timing for carbureted versions is 10° BTDC at idle, while
EFI models rely on ECU-controlled timing advance.
| Tightening Torques |
Cylinder head bolts: stage one 25 Nm (18 lb-ft), stage two 50 Nm (37
lb-ft), final 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: 160 Nm (118 lb-ft).
Flywheel bolts: 85 Nm (63 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).
Spark plugs: 18 Nm (13 lb-ft).
Drain plug: 40 Nm (30 lb-ft).
| Vehicle Applications |
The Mitsubishi 4G15 engine was used in a broad range of vehicles from
the early 1980s through the 2000s, both under the Mitsubishi brand and
other manufacturers through joint ventures.
Common applications include:
– Mitsubishi Mirage (1983–2003)
– Mitsubishi Colt (1984–2003)
– Mitsubishi Lancer (1983–2005)
– Mitsubishi Space Star and Dingo
– Proton Wira and Satria (licensed versions)
– Hyundai Excel (early versions under license)
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