Mitsubishi G32B Specifications
| Engine Model: Mitsubishi G32B |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve liquid-cooled gasoline |
| Total Displacement: 97.5 cu.in (1.59 L) |
| Rated Engine Power: 86-120 Hp (63-90 kW) at 5500 rpm |
| Fuel System Type: Carburetor or Electronic fuel injection |
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The Mitsubishi G32B is a 1.6-liter inline-four gasoline
engine belonging to the Saturn (4G3) engine family, produced from the late 1970s
through the mid-1990s. This powerplant is distinguished by the implementation of
the MCA-Jet (Mitsubishi Clean Air) system, an emissions control technology
developed to meet increasingly stringent exhaust regulations without the
performance penalties associated with early catalytic converter systems.
The MCA-Jet system utilized a secondary intake passage directing a concentrated
air stream - or in later iterations, a lean air-fuel mixture - through a smaller
“jet valve” positioned beside the conventional intake valve. This configuration
generated swirl within the combustion chamber, promoting more complete
combustion and reducing hydrocarbon and carbon monoxide emissions at the source.
The G32B was engineered as a robust, serviceable powerplant intended for global
markets where reliability under varied operating conditions was paramount. Its
cast iron cylinder block and aluminum cylinder head construction reflected the
prevailing design philosophy of the era, prioritizing durability and thermal
stability.
The engine was offered in naturally aspirated carbureted configurations for
mainstream passenger cars and light commercial vehicles, alongside a
turbocharged electronic fuel-injected variant for sport-oriented models such as
the Mitsubishi Cordia and Tredia. The G32B’s versatility extended to industrial
applications, where its compact dimensions and torque characteristics made it
suitable for skid-steer loaders, forklifts, and other material handling
equipment manufactured under license by companies such as Bobcat.
The G32B is a four-stroke, water-cooled, naturally aspirated or turbocharged
gasoline engine configured for longitudinal or transverse mounting depending on
vehicle application. The engine architecture incorporates the MCA-Jet system as
a defining feature across all variants, with the jet valve integrated into the
cylinder head adjacent to each primary intake valve.
Engine Type: Inline-4, 4-cycle, water-cooled, gasoline.
Displacement: 1,597 cc (97.5 cu.in).
Bore: 76.9 mm (3.03 in).
Stroke: 86.0 mm (3.39 in).
Firing Order: 1-3-4-2.
Valvetrain: SOHC, 8-valve (2 valves per cylinder plus 4 jet valves).
MCA-Jet System: Secondary jet valve per cylinder with dedicated passage.
Naturally Aspirated (Carbureted)
Compression Ratio: 8.5:1 to 9.5:1 depending on market and emissions
specification.
Maximum Power: 63-68 kW (86-92 hp) at 5,000-5,500 rpm.
Maximum Torque: 132-133 Nm (97-98 lb-ft) at 3,000-3,500 rpm.
Induction: Single downdraft two-barrel carburetor.
Turbocharged (ECI Turbo)
Compression Ratio: 7.6:1 to 8.5:1 depending on boost pressure configuration.
Maximum Power: 86-90 kW (115-120 hp) at 5,500 rpm.
Maximum Torque: 167-172 Nm (123-127 lb-ft) at 3,000 rpm.
Induction: Single turbocharger with Mitsubishi Electronic Controlled Injection
(ECI).
The cylinder block is manufactured from gray cast iron
using a permanent mold casting process, providing the structural rigidity
required for the engine’s intended service life in both passenger car and
industrial applications. The block incorporates a closed-deck design where the
cylinder bores are fully supported by the upper deck surface, enhancing cylinder
bore roundness under head bolt clamping loads and combustion pressures. This
closed-deck configuration also contributes to improved head gasket sealing
compared to open-deck designs.
The cylinder bores are machined directly into the iron casting with a honed
surface finish that retains lubricating oil to facilitate ring sealing and
reduce friction. The block features a five-main-bearing crankshaft support
structure, with the bearing webs integrated into the lower crankcase region.
Water passages surround the full length of each cylinder bore, with coolant flow
directed from the water pump into the block before rising into the cylinder
head.
The engine mounting configuration incorporates bosses cast into the block sides
and front cover to accommodate the vehicle-specific mounting brackets required
for both longitudinal and transverse installations. A cast aluminum or stamped
steel oil pan is secured to the lower crankcase flange, serving as both a
lubricant reservoir and a structural element contributing to overall engine
rigidity.
Block Material: Gray cast iron
Bore Diameter: 76.9 mm (3.03 in)
Cylinder Configuration: Inline, closed-deck
Main Bearing Quantity: 5
Main Bearing Cap Design: Cast iron, two-bolt attachment
The cylinder head is constructed from aluminum alloy
using a permanent mold casting process, selected for its favorable thermal
conductivity relative to cast iron. The cross-flow port configuration places
intake ports on one side of the head and exhaust ports on the opposite side,
promoting efficient airflow through the combustion chambers. The SOHC valvetrain
operates eight conventional valves - two per cylinder - with the MCA-Jet system
adding a secondary jet valve adjacent to each conventional intake valve.
The single camshaft is supported in five bearing journals machined directly into
the cylinder head casting. The camshaft acts on rocker arms that pivot on
individual shafts, converting cam lobe lift into valve motion. The MCA-Jet
system incorporates a separate set of rocker arms actuating the jet valves, with
the jet valve rocker arms positioned alongside the primary rocker arms and
actuated by additional cam lobes on the same camshaft. The jet valves are
smaller-diameter poppet valves with reduced mass, permitting rapid opening and
closing response.
The combustion chamber is of a compact wedge design, with the MCA-Jet passage
directing a high-velocity air stream or lean mixture toward the spark plug
electrode. This induced swirl motion accelerates flame propagation, reducing the
ignition advance required for complete combustion and lowering exhaust
emissions. The cylinder head incorporates pressed-in valve seat inserts for both
intake and exhaust valves, with the exhaust seats manufactured from a
heat-resistant material to withstand elevated temperatures.
Valve clearance adjustment requires periodic manual intervention using shims or
adjusting screws, depending on production era. The valve mechanism employs a
screw-and-locknut adjuster on earlier rocker arm assemblies, with a threaded
adjuster contacting the valve stem tip.
Head Material: Aluminum alloy
Valve Configuration: SOHC, 8 primary valves plus 4 MCA-Jet valves
Primary Valve Diameter (Intake): 42.0 mm (1.65 in)
Primary Valve Diameter (Exhaust): 35.0 mm (1.38 in)
Jet Valve Diameter: 6.0-8.0 mm (0.24-0.31 in) depending on variant
Valve Stem Diameter (Primary): 8.0 mm (0.31 in)
Valve Seat Angle: 45 degrees
Camshaft Drive: Timing belt with automatic tensioner
Valve Clearance (Cold, Intake): 0.15 mm (0.006 in)
Valve Clearance (Cold, Exhaust): 0.25 mm (0.010 in)
Interference Engine: Yes - valve-to-piston contact occurs if timing belt fails
The fuel system configuration varies substantially
between naturally aspirated and turbocharged G32B variants, reflecting the
engine’s application range from economy-oriented passenger cars to
performance-oriented sport coupes.
Naturally aspirated variants utilize a single downdraft two-barrel carburetor
manufactured by Mikuni or Solex, depending on production source. The carburetor
incorporates an automatic choke mechanism, fast idle cam, and accelerator pump
for cold start and transient enrichment. A mechanical fuel pump mounted on the
cylinder block draws fuel from the tank and delivers it to the carburetor float
chamber at regulated pressure. The carburetor is integrated with the MCA-Jet
system through calibrated vacuum passages that control jet valve operation based
on engine load and speed.
Turbocharged variants employ the Mitsubishi Electronic Controlled Injection
(ECI) system, a multi-point fuel injection arrangement with individual injectors
positioned in the intake manifold runners. The system utilizes an air flow meter
measuring intake air volume, with the engine control unit calculating injector
pulse width based on air flow, engine speed, coolant temperature, and manifold
pressure. Fuel is delivered by an in-tank electric pump at regulated pressure
maintained by a vacuum-referenced pressure regulator. The turbocharger is a
single Mitsubishi TD04 or similar unit mounted to the exhaust manifold, with an
air-to-air intercooler reducing intake air temperature on certain applications.
Fuel System (NA): Single downdraft two-barrel carburetor.
Fuel System (Turbo): Multi-point electronic fuel injection.
Fuel Pressure (Turbo): 250-280 kPa (36-41 psi) with vacuum line connected.
Fuel Requirement: 91 octane (RON) for naturally aspirated; 95 octane (RON) for
turbocharged.
The lubrication system is a fully pressurized, wet-sump
design with a gear-type oil pump mounted internally within the timing case and
driven by the crankshaft nose. The oil pump utilizes a pair of meshing gears -
one driven by the crankshaft and one idler gear - to generate flow with positive
displacement characteristics.
Oil is drawn from the stamped steel or cast aluminum oil pan through a mesh
strainer positioned at the sump’s lowest point. Pressurized oil passes through a
full-flow, replaceable oil filter mounted externally on the cylinder block. The
filter incorporates a bypass valve that permits oil flow to continue if the
filter element becomes restricted. From the filter, oil enters the main oil
gallery cast longitudinally through the cylinder block, supplying the crankshaft
main bearings, connecting rod bearings, camshaft bearings, and rocker arm
assemblies.
The turbocharged variant incorporates an additional oil feed line supplying the
turbocharger center housing bearings, with a restricted orifice controlling flow
rate. An oil drain line returns oil from the turbocharger to the oil pan. Some
turbocharged applications include an external oil cooler - either air-to-oil or
water-to-oil - to maintain lubricant temperature under sustained high-load
operation.
Oil Type: SAE 10W-30 or 10W-40; API SE, SF, or SG classification
Oil Capacity: 3.3-3.7 L (3.5-3.9 US qt) depending on oil pan configuration
Oil Pressure (at idle, warm): 50-100 kPa (7-15 psi)
Oil Pressure (at 3,000 rpm): 300-400 kPa (44-58 psi)
Oil Pump Type: Gear-type, crankshaft-driven
The cooling system is a pressurized, liquid-cooled
design with a belt-driven centrifugal water pump mounted on the front of the
cylinder block. The water pump impeller circulates coolant through the cylinder
block water jackets, cylinder head water passages, heater core, and radiator.
The system is designed to maintain consistent operating temperatures across all
four cylinders, with coolant flow directed preferentially to areas of highest
thermal loading near the exhaust valve seats and combustion chamber surfaces.
A wax-pellet thermostat is mounted in a housing on the water pump inlet or
cylinder head outlet, depending on variant. The thermostat regulates coolant
flow to the radiator, with a bypass circuit permitting circulation within the
engine during warm-up. The thermostat begins opening at a calibrated temperature
and achieves full opening within a defined temperature range.
The radiator is a cross-flow or down-flow construction with copper-brass or
aluminum-plastic core depending on vehicle application. An engine-driven fan
with a viscous clutch or an electric fan provides forced airflow through the
radiator. The cooling system capacity is sized to accommodate the thermal
demands of both naturally aspirated and turbocharged configurations.
Coolant Type: Ethylene-glycol based antifreeze meeting Mitsubishi specification
Coolant Capacity: 5.5-6.5 L (5.8-6.9 US qt) depending on radiator configuration
Thermostat Opening Temperature: 82-88 °C (180-190 °F)
Radiator Cap Pressure: 90-110 kPa (13-16 psi)
Water Pump Type: Centrifugal, belt-driven
Ignition System: The G32B employs a distributor-based
ignition system with the distributor mounted on the cylinder head or cylinder
block depending on configuration. The distributor houses a breaker-point
assembly on early variants, with later variants incorporating a breakerless
electronic ignition system using a magnetic pickup and ignition module. The
distributor is driven by a gear on the camshaft or an auxiliary shaft, with
centrifugal and vacuum advance mechanisms adjusting ignition timing based on
engine speed and load.
Timing Drive: The engine utilizes a rubber timing belt with fabric reinforcement
to drive the camshaft from the crankshaft sprocket. The belt also drives the
water pump on most configurations. A spring-loaded automatic tensioner pulley
maintains belt tension, compensating for belt stretch and thermal expansion. The
G32B is an interference engine; timing belt failure results in piston-to-valve
contact causing significant engine damage.
Intake System: The intake manifold is an aluminum casting with individual
runners for each cylinder. Naturally aspirated carbureted variants incorporate a
single-plane manifold with the carburetor flange positioned centrally.
Turbocharged variants utilize a tuned intake manifold with injector bosses
machined into each runner. The MCA-Jet system incorporates separate passages
within the intake manifold directing the jet valve air supply.
Exhaust System: The exhaust manifold is a cast iron single-piece design
collecting exhaust gases from all four cylinders into a single outlet.
Turbocharged variants utilize a dedicated turbocharger flange integrated into
the exhaust manifold casting. The exhaust system incorporates a catalytic
converter on vehicles equipped for markets with emissions regulations requiring
such devices.
Overall Length: 570 mm (22.4 in)
Overall Width: 590 mm (23.2 in)
Overall Height: 660 mm (26.0 in)
Dry Weight (complete engine): 125 kg (276 lb)
Engine Oil Change: 5,000 km (3,100 mi) or 6 months.
Engine Oil Filter Change: At every oil change. Timing Belt Replacement:
80,000-100,000 km (50,000-62,000 mi) depending on market. Timing Belt Tensioner
Inspection: Replace with timing belt. Valve Clearance Inspection: Every 30,000
km (18,600 mi); adjust as required.
Spark Plug Replacement: 20,000 km (12,400 mi) for standard plugs; 40,000 km
(25,000 mi) for platinum. Spark Plug Gap (NA): 0.8-0.9 mm (0.031-0.035 in).
Spark Plug Gap (Turbo): 0.7-0.8 mm (0.028-0.031 in). Coolant Replacement: 40,000
km (25,000 mi) or 2 years.
Drive Belt (Accessory) Inspection: Every 15,000 km (9,300 mi). Air Filter
Replacement: 30,000 km (18,600 mi). Fuel Filter Replacement: 40,000 km (25,000
mi) for carbureted; 60,000 km (37,000 mi) for EFI. Carburetor Adjustment: As
required for idle speed and mixture compliance.
Cylinder Head Bolts (M11 x 1.5), 1st pass: 40 Nm (30
lb-ft)
Cylinder Head Bolts (M11 x 1.5), 2nd pass: 70 Nm (52 lb-ft)
Cylinder Head Bolts (M11 x 1.5), Final pass: 95-105 Nm (70-77 lb-ft)
Main Bearing Cap Bolts (M10 x 1.25), 1st pass: 25 Nm (18 lb-ft)
Main Bearing Cap Bolts (M10 x 1.25), Final pass: 55-60 Nm (41-44 lb-ft)
Connecting Rod Cap Bolts (M8 x 1.25), 1st pass: 15 Nm (11 lb-ft)
Connecting Rod Cap Bolts (M8 x 1.25), Final pass: 40-45 Nm (30-33 lb-ft)
Camshaft Bearing Cap Bolts: 20-25 Nm (15-18 lb-ft)
Rocker Arm Shaft Bolts: 25-30 Nm (18-22 lb-ft)
Intake Manifold Bolts (M8 x 1.25): 20-25 Nm (15-18 lb-ft)
Exhaust Manifold Nuts (M8 x 1.25): 20-30 Nm (15-22 lb-ft)
Spark Plugs: 20-30 Nm (15-22 lb-ft)
Oil Pan Bolts (M6 x 1.0): 10-12 Nm (89-106 lb-in)
Water Pump Bolts (M8 x 1.25): 20-25 Nm (15-18 lb-ft)
Timing Belt Tensioner Bolt: 20-25 Nm (15-18 lb-ft)
Crankshaft Pulley Bolt (M14 x 1.5): 80 Nm (59 lb-ft)
Final pass: 90-100 Nm (66-74 lb-ft)
Flywheel / Drive Plate Bolts (M10 x 1.25): 65-75 Nm (48-55 lb-ft)
The Mitsubishi G32B engine was deployed across a
diverse range of passenger cars, light commercial vehicles, and industrial
equipment produced from the late 1970s through the mid-1990s.
Mitsubishi Passenger Cars:
Mitsubishi Lancer / Lancer EX (A170, A172, A173): 1978-1987, naturally aspirated
carbureted.
Mitsubishi Celeste (A170): 1978-1981, naturally aspirated carbureted.
Mitsubishi Cordia (A210, A211, A212): 1982-1989, naturally aspirated carbureted
and turbocharged.
Mitsubishi Tredia (A210, A211, A212): 1982-1989, naturally aspirated carbureted
and turbocharged.
Mitsubishi Mirage / Colt (C10, C20 series): Selected markets; naturally
aspirated carbureted.
Mitsubishi Galant / Sigma: Early 1980s applications in certain export markets.
Mitsubishi Light Commercial Vehicles:
Mitsubishi L200 / Mighty Max pickup: 1980-1986, naturally aspirated carbureted.
Mitsubishi L300 / Delica van: 1979-1986, naturally aspirated carbureted.
Mitsubishi Chariot / Space Wagon: Early 1980s, naturally aspirated carbureted.
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