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Mitsubishi 4G32 Specifications
| Engine Model: Mitsubishi 4G32 |
| Engine Type: 4-cycle inline 4-cylinder OHC 8-valve liquid-cooled gasoline |
| Total Displacement: 99.2 cu.in (1.59 L) |
| Rated Engine Power: 70-110 Hp (52-82 kW) at 6000 rpm |
| Fuel System Type: Single downdraft carburetor or dual side-draft carburetor |
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| General Technical Data |
The Mitsubishi 4G32 is one of the most historically significant engines in Mitsubishi’s early passenger-car powertrain lineup. Introduced in the late 1960s, it formed part of the SATURN engine family, a range that helped Mitsubishi transition from simple economy engines to more refined and performance-capable designs. The 4G32 displaced 1.6 liters and served not only as a dependable everyday engine in vehicles such as the Galant, Colt, Lancer, and Celeste, but also as the basis for high-performance road and motorsport applications.
Its robust cast-iron block, aluminum cylinder
head, overhead camshaft valvetrain, and strong bottom-end design
provided durability suitable for rally competition. Later
hemispherical-head designs and the 4G32T turbocharged variant increased
the engine’s performance ceiling dramatically. As a result, the engine
became well known among enthusiasts for its balance of simplicity,
mechanical accessibility, and tuning potential.
The 4G32 has a total displacement of 1,598 cc, achieved with a bore of
77.0 mm (3.03 inches) and a stroke of 86.0 mm (3.39 inches). The
undersquare configuration favors torque production at lower RPM and
gives the engine strong pulling power for its displacement. The block is
constructed of cast iron, offering excellent rigidity and long-term
durability.
Five main bearings support the crankshaft,
improving smoothness and extending the service life of rotating
components. The crankshaft itself is forged steel, and the connecting
rods are also forged, allowing the engine to withstand high mechanical
loads, especially in tuned and motorsport applications.
The cylinder head on most common 4G32 versions is cast aluminum with a
two-valve-per-cylinder arrangement. Early configurations used a
wedge-style combustion chamber, providing a balance of efficiency and
ease of manufacture. Later high-performance variants introduced
hemispherical chambers paired with twin side-draft carburetors, which
significantly improved volumetric efficiency and power output. The
camshaft is driven by a toothed timing belt located at the front of the
engine. The valvetrain uses rocker arms, with valve clearances adjusted
by screw-and-locknut adjusters-simple, reliable, and easy to service.
Compression ratios varied depending on market and configuration.
Standard single-carburetor versions ranged from 8.5:1 to 9.5:1.
High-performance twin-carburetor and hemispherical-head engines
generally used ratios from 9.0:1 to 10.0:1, while the turbocharged 4G32T
maintained a reduced compression ratio near 7.5:1 to accommodate boost
levels without detonation.
Power outputs ranged broadly: base engines
produced 70 to 92 horsepower (52-69 kW), twin-carburetor designs
produced roughly 100 to 110 horsepower (75-82 kW), and the turbocharged
4G32T produced approximately 125 to 150 horsepower (93-112 kW),
depending on boost pressure and tuning. Torque figures ranged from 115
to 130 Nm (85-96 lb-ft) for naturally aspirated configurations, while
the turbocharged version produced up to 190 Nm (140 lb-ft).
Idle speed for most versions was set between 750 and 850 rpm. Redline
varied slightly depending on market, but generally remained around 6,000
to 6,500 rpm. The firing order for all 4G32 engines is 1-3-4-2. Because
of its strong construction, the engine was often used as a base for
high-performance builds, with racing versions producing significantly
more power through increased compression, aggressive camshaft profiles,
ported heads, and improved carburetion.
| Fuel System |
The 4G32 was originally designed for carbureted fuel delivery. Standard models used a single downdraft carburetor-typically a Mikuni, Solex, or Nikki unit-with vacuum-controlled secondary throttle plates. These carburetors provided predictable operation and good fuel atomization for everyday driving. Fuel was delivered by a mechanically driven diaphragm pump producing approximately 20 to 30 kPa (3-4 psi).
Standard fuel lines routed fuel from a rear-mounted tank to a front
engine bay filter and then to the carburetor inlet. Air-fuel mixture
control was managed internally within the carburetor through primary and
secondary venturi circuits, idle mixture screws, and emulsion tubes.
Performance-oriented variants of the 4G32 used dual side-draft
carburetors, commonly Mikuni-Solex or Weber DCOE equivalents. These
carburetors allowed each cylinder pair to receive a more direct airflow
path and increased tuning flexibility. As a result, the twin-carburetor
4G32 engines demonstrated significantly stronger throttle response and
higher top-end power.
The turbocharged 4G32T used a blow-through carburetion system. The
carburetor was sealed and pressurized by the turbocharger, requiring
reinforced throttle shafts, improved float design, and a pressurized
fuel bowl. Fuel delivery was provided by an electric pump capable of
supplying consistent pressure under boost.
A pressure-referenced regulator ensured stable mixture control. The 4G32T typically operated with boost pressures between 6 and 9 psi (0.4-0.6 bar). Higher octane fuel-95 RON (91 AKI) or above-was required to prevent detonation.
| Lubrication System |
The lubrication system is a full-pressure wet-sump design. A trochoid-type oil pump driven by the crankshaft pressurizes the oil, distributing it through internal galleries to the crankshaft bearings, connecting rod journals, camshaft bearings, and rocker arms. Piston cooling is provided partially by oil splash and, in some later versions, by dedicated oil jets.
A spin-on replaceable oil filter is mounted on the block's side. Oil
pressure typically measures around 250 kPa (36 psi) at 3,000 rpm, and
about 70 kPa (10 psi) at idle. Oil capacity is roughly 3.5 liters (3.7
US quarts). Recommended oil viscosity depends on climate, but SAE 10W-30
or 10W-40 is commonly specified.
Turbocharged models operate under higher thermal loads and therefore
require more frequent oil changes and high-quality oil with strong
thermal stability. Turbocharger lubrication is provided by a dedicated
feed line from the main gallery and a gravity return line into the sump.
| Cooling System |
The cooling system is a liquid-cooled, forced-circulation type with a belt-driven centrifugal water pump. Coolant flows through the cast-iron block, aluminum head, radiator, and heater core. A wax-type thermostat opens at approximately 82 C (180°F) and is fully open by about 95 C (203°F).
Cooling system pressure is regulated by a radiator cap rated around 88
kPa (13 psi). Total coolant capacity is approximately 6 liters (6.3 US
quarts).
Turbocharged versions use enhanced cooling systems, including larger
radiators and, in some models, oil coolers. Intercoolers were added on
performance variants to cool charge air, improving efficiency and
reducing the risk of detonation.
| Intake and Exhaust Systems |
The intake manifold is made of cast aluminum on most versions. Standard
engines use long-runner intake manifolds optimized for low-speed torque.
Twin-carburetor systems use individual runner intakes for improved
high-RPM breathing. Turbocharged engines employ a sealed intake plenum
designed to withstand boost pressure.
The exhaust manifold on naturally aspirated engines is cast iron with
equal-length runners. Turbocharged 4G32T engines use a compact turbo
manifold that feeds exhaust gases into a small Mitsubishi TC05-type
turbocharger.
| Ignition System |
Early versions of the 4G32 used a conventional mechanical distributor
with breaker points, centrifugal advance, and vacuum advance. Regular
maintenance of dwell angle and breaker point gap was necessary. Spark
plugs were gapped at 0.8 mm (0.032 inches). Later engines used
electronic ignition with an ignition module for improved reliability and
more stable spark delivery.
Turbocharged engines used a reinforced distributor and higher-voltage
coil to ensure proper spark under pressurized conditions. Timing was
often retarded under load to prevent detonation. Performance versions
sometimes employed aftermarket ignition boxes to stabilize spark at high
RPM.
| Valve Train |
The valvetrain uses an overhead camshaft configuration with rocker arms. The camshaft is driven by a toothed rubber timing belt, which requires replacement every 80,000 to 100,000 km (50,000-60,000 miles). Valve clearances are set manually and should be checked at regular intervals. Cold clearance values are approximately 0.15 mm (0.006 inches) intake and 0.25 mm (0.010 inches) exhaust.
| Dimensions and Weight |
0Overall length: 620 mm (24.4 inches)
Width: 560 mm (22.0 inches)
Height: 630 mm (24.8 inches)
Dry weight: 135-145 kg (298-320 lbs); turbocharged versions roughly 150
kg (330 lbs)
| Maintenance Data |
Recommended service intervals:
Oil and filter: every 5,000 km (3,000 mi)
Valve adjustment: every 20,000 km (12,000 mi)
Air filter: every 20,000 km (12,000 mi)
Spark plugs: every 10,000-20,000 km
Timing belt: every 80,000-100,000 km
Coolant: every 40,000 km
| Tightening Torques |
Cylinder head bolts: 40 Nm, then 80 Nm, plus 90 degrees
Main bearing cap bolts: 75 Nm
Connecting rod bolts: 40 Nm plus 60 degrees
Camshaft sprocket bolt: 65 Nm
Flywheel bolts: 85 Nm plus 45 degrees
Spark plugs: 25 Nm
Drain plug: 35 Nm
Intake manifold bolts: 22 Nm
Exhaust manifold nuts: 30 Nm
| Vehicle Applications |
The 4G32 powered:
Mitsubishi Galant (A50, A70)
Mitsubishi Lancer (A70)
Mitsubishi Colt
Mitsubishi Lancer EX
Mitsubishi Celeste
Various export pickups and industrial variants
Turbocharged 4G32T: Lancer EX Turbo and homologation rally cars
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