Mitsubishi G52B Specifications
| Engine Model: Mitsubishi G52B |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve liquid-cooled gasoline |
| Total Displacement: 121.7 cu.in (1.99 L) |
| Rated Engine Power: 95-100 Hp (71-75 kW) at 5500 rpm |
| Fuel System Type: Downdraft carburetor |
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The Mitsubishi G52B is a 2.0-liter inline-four gasoline
engine belonging to the Astron (4G5) family. Introduced in the 1970s and
produced through the 1980s, the G52B served as a workhorse powertrain for
Mitsubishi’s larger sedans, pickup trucks, and early sport utility vehicles. The
engine is designated 4G52 in later Mitsubishi nomenclature.
Characterized by its cast iron cylinder block, aluminum alloy cylinder head, and
single overhead camshaft (SOHC) operating two valves per cylinder, the G52B
incorporated advanced technologies for its era including dual balancing shafts
(Silent Shaft system) and MCA-Jet emissions control with auxiliary jet valves.
The engine was offered in both single-carburetor and twin-carburetor
configurations, providing a range of power outputs suitable for diverse
applications from passenger cars to light commercial vehicles.
Engine Type: Inline 4-cylinder, 4-cycle, water-cooled, gasoline.
Displacement: 1,995 cc (121.7 cu.in).
Bore: 84.0 mm (3.31 in).
Stroke: 90.0 mm (3.54 in).
Compression Ratio: 8.5:1 for standard variants.
Compression Ratio: 9.5:1 for high-compression variants (twin-carburetor).
Firing Order: 1-3-4-2.
Maximum Power: 95-100 hp (71-75 kW) @ 5,500 rpm.
Maximum Torque: 157-160 Nm (116-118 lb-ft) @ 3,500 rpm.
Valvetrain Configuration: Single Overhead Camshaft (SOHC) operating 8 valves (2
valves per cylinder). The camshaft is driven by a silent timing chain. Valve
clearances are adjusted manually using threaded adjusters on rocker arms with
locking nuts. MCA-Jet system incorporates an additional jet valve per cylinder
for emissions control, requiring separate clearance adjustment.
The cylinder block is manufactured from cast iron with
a deep-skirt design extending below the crankshaft centerline. Bore diameter
measures 84.0 mm (3.31 in). The block features a closed-deck design with
pressed-in cast iron cylinder liners that are replaceable during major
overhauls. The crankshaft is forged steel with eight counterweights, supported
by five main bearings.
The block incorporates dual balancing shafts (Silent Shafts) mounted within the
crankcase to cancel secondary vibrations. These shafts rotate at twice engine
speed in opposite directions and are driven by a secondary chain from the
crankshaft. The balancing shaft system was a Mitsubishi innovation that
significantly reduced vibration in inline-four engines.
The cylinder head is manufactured from aluminum alloy
with a cross-flow port architecture. Valves: 8 primary valves (4 intake, 4
exhaust) plus 4 jet valves (one per cylinder) for MCA-Jet emissions control.
Intake Valve Diameter: 42.0 mm (1.65 in). Exhaust Valve Diameter: 35.0 mm (1.38
in).
Jet Valve Diameter: 6.0 mm (0.24 in). Jet valves introduce a small quantity of
additional air-fuel mixture into the combustion chamber to promote more complete
combustion and reduce hydrocarbon and carbon monoxide emissions.
Valve Stem Diameter: 8.0 mm (0.31 in) for primary valves; 5.0 mm (0.20 in) for
jet valves. Valve Seat Inserts: Press-fit inserts; exhaust valve seats are
manufactured from heat-resistant alloy. Valve Guides: Cast iron guides pressed
into the cylinder head.
Valve Adjustment: Mechanical adjusters with threaded rocker arms and lock nuts
for primary valves. Jet valves utilize separate adjusters. Valve clearance is
set with the engine hot (operating temperature). Primary intake clearance: 0.15
mm (0.006 in); Primary exhaust clearance: 0.25 mm (0.010 in); Jet valve
clearance: 0.25 mm (0.010 in).
Camshaft: Chilled cast iron camshaft with induction-hardened lobes, supported by
five bearings and driven by a silent timing chain. Combustion Chamber:
Hemispherical design optimized for the MCA-Jet system, with the jet valve
positioned adjacent to the primary intake valve to create controlled swirl and
turbulence during combustion.
The fuel system employs a downdraft carburetor
configuration with single or twin carburetor arrangements. Carburetor Type:
Single downdraft two-barrel carburetor (Mikuni or Solex) for standard variants;
twin downdraft carburetors for high-output variants. Fuel Pump: Mechanical
diaphragm pump mounted to the cylinder head, operated by an eccentric lobe on
the camshaft.
Fuel Filtration: In-line fuel filter mounted in the engine compartment. Intake
Manifold: Cast aluminum manifold with individual runners per cylinder.
Twin-carburetor variants utilize a dual-plane manifold with separate runners for
each carburetor.
MCA-Jet System: A separate passage from the intake manifold supplies the jet
valves with a calibrated air-fuel mixture. A jet valve control solenoid (on
later variants) modulates the mixture under deceleration to prevent backfiring.
The lubrication system is a full-flow, pressurized
design utilizing a rotor-type oil pump driven by the crankshaft. Oil Pump Type:
Internal gear (gerotor) pump mounted to the front of the crankshaft, housed
within the front timing cover assembly. Oil Capacity: 4.0-4.5 liters (4.2-4.8
qt) including oil filter replacement.
Recommended Oil Viscosity: 10W-30 or 10W-40. Oil Quality Requirement: API SE,
SF, SG, or later classifications. Oil Pressure: At warm idle, pressure ranges
from 0.5-1.5 bar (7-22 psi). At 3,000 rpm, pressure reaches 3.0-4.0 bar (44-58
psi). Oil Filter: Full-flow spin-on canister type mounted to the cylinder block.
Crankcase Ventilation: Positive Crankcase Ventilation (PCV) system with a PCV
valve mounted in the intake manifold.
The cooling system is pressurized and utilizes a
centrifugal water pump driven by the accessory drive belt. Water Pump Type:
Centrifugal pump with a cast iron housing and stamped steel impeller.
Thermostat: Wax-pellet type located in the coolant outlet housing. Opening
temperature is 82-88 °C (180-190 °F).
Coolant Capacity: 6.0-7.0 liters (6.3-7.4 qt) inclusive of engine block, heater
core, and radiator. Coolant Specification: Ethylene glycol-based coolant with
corrosion inhibitors suitable for mixed-metal (cast iron and aluminum) engine
construction. System Pressure: Radiator cap rated at 0.9 bar (13 psi).
Radiator: Cross-flow copper or aluminum core depending on production year.
Cooling fan configuration consists of an engine-driven mechanical fan with a
viscous clutch on later variants; direct-drive fan on earlier models.
Ignition System: Distributor-based ignition with a
breaker-point or electronic ignition system depending on production year. Early
variants utilized contact breaker points; later variants incorporated a
Hall-effect or optical electronic ignition module. The distributor is driven by
the camshaft and incorporates mechanical and vacuum advance mechanisms. Spark
Plug Type: NGK BP6ES or BPR6ES. Spark Plug Gap: 0.7-0.9 mm (0.028-0.035 in).
Timing System: Dual-chain configuration. A primary silent timing chain drives
the camshaft from the crankshaft. A secondary chain drives the dual balancing
shafts (Silent Shafts). Hydraulic or spring-loaded tensioners maintain chain
tension. The chain system is maintenance-free under normal operating conditions,
with no scheduled replacement interval.
Exhaust System: Cast iron exhaust manifold with a single exhaust outlet.
Emissions equipment varies by market; export variants incorporate a catalytic
converter and exhaust gas recirculation (EGR) system.
Intake System: Air induction utilizes a single air cleaner housing with a
replaceable paper element. The air cleaner incorporates a thermostatically
controlled pre-heat system that draws warm air from the exhaust manifold during
cold starts to improve driveability.
Starting System: 12-volt electric starter with a solenoid. A cold-start
enrichment circuit within the carburetor provides additional fuel during engine
warm-up.
Overall Length: 620 mm (24.4 in) measured from
accessory drive pulley face to transmission mounting flange.
Overall Width: 590 mm (23.2 in) inclusive of intake manifold, carburetor, and
exhaust manifold.
Overall Height: 680 mm (26.8 in) from oil pan bottom surface to valve cover top
surface.
Dry Weight: 135-145 kg (298-320 lb) depending on carburetor configuration and
accessory drive components.
Valve Clearance (hot): Primary intake 0.15 mm (0.006
in); Primary exhaust 0.25 mm (0.010 in); Jet valve 0.25 mm (0.010 in).
Adjustment interval is 40,000 km (25,000 miles). Timing Chain Inspection: Chain
and tensioner inspection recommended at 80,000 km (50,000 miles). Replacement is
condition-based; no scheduled replacement interval.
Carburetor Adjustment: Idle mixture and speed adjustments performed with engine
at operating temperature. Idle speed is 700-750 rpm. Spark Plug Replacement
Interval: 20,000 km (12,500 miles) for standard plugs. Drive Belt Tension
(Accessory): 10-12 mm (0.39-0.47 in) deflection under 10 kg (22 lb) of force at
the midpoint of the longest span.
Coolant Change Interval: 40,000 km (25,000 miles) or 2 years. Engine Oil Change
Interval: 5,000 km (3,100 miles) or 6 months. Idle Speed (warm, neutral):
700-750 rpm. Ignition Timing (base): 5°-8° BTDC at idle with vacuum advance line
disconnected. Fuel Pump Pressure: 0.2-0.3 bar (3-4 psi) for mechanical fuel
pump.
Cylinder Head Bolts (cold), Step 1: 30 Nm (22 lb-ft).
Cylinder Head Bolts (cold), Step 2: 60 Nm (44 lb-ft).
Cylinder Head Bolts (cold), Step 3: 90-100 Nm (66-74 lb-ft).
Crankshaft Damper Pulley Bolt: 150-170 Nm (111-125 lb-ft).
Connecting Rod Cap Nuts: 45-50 Nm (33-37 lb-ft).
Main Bearing Cap Bolts: 65-70 Nm (48-52 lb-ft).
Camshaft Sprocket Bolt: 60-70 Nm (44-52 lb-ft).
Camshaft Bearing Cap Bolts: 20-25 Nm (15-18 lb-ft).
Valve Cover Nuts: 5-8 Nm (4-6 lb-ft).
Rocker Arm Shaft Bolts: 20-25 Nm (15-18 lb-ft).
Intake Manifold Nuts: 20-25 Nm (15-18 lb-ft).
Exhaust Manifold Nuts: 30-35 Nm (22-26 lb-ft).
Oil Pan Bolts: 10-12 Nm (7-9 lb-ft).
Oil Pump Mounting Bolts: 10-12 Nm (7-9 lb-ft).
Timing Chain Tensioner Bolts: 20-25 Nm (15-18 lb-ft).
Water Pump Bolts: 20-25 Nm (15-18 lb-ft).
Carburetor Mounting Nuts: 20-25 Nm (15-18 lb-ft).
Flywheel / Drive Plate Bolts: 80-90 Nm (59-66 lb-ft).
Spark Plugs: 20-25 Nm (15-18 lb-ft).
Mitsubishi Pajero / Montero (L040 / First Generation):
1982-1990. The G52B powered entry-level and mid-range variants of the
first-generation Pajero, providing reliable power for off-road applications.
Mitsubishi L200 / Forte / Mighty Max (Pickup): 1978-1986. The G52B served as a
gasoline powertrain option for Mitsubishi’s compact pickup trucks across global
markets.
Mitsubishi Galant / Sigma / Sapporo: 1976-1984. The G52B was utilized in the
Galant, Sigma, and Sapporo sedans and coupes, with twin-carburetor variants
appearing in higher-performance models.
Mitsubishi Delica / L300: 1979-1986. The G52B powered Delica vans and L300
commercial vehicles in markets where gasoline engines were preferred over
diesel.
Mitsubishi Celeste / Cordia / Tredia: 1978-1984. The G52B was installed in the
Celeste coupe and the Cordia/Tredia compact sedan and coupe lineup, with
twin-carburetor variants offering increased power output.
Mitsubishi Starion: Early 1980s. Certain base-market Starion variants utilized
the naturally aspirated G52B before the introduction of turbocharged 4G5 and 4G6
engines.
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