Mitsubishi 6G73 Specifications
| Engine Model: Mitsubishi 6G73 |
| Engine Type: 4-cycle 6-cylinder V-block liquid-cooled gasoline |
| Total Displacement: 152.4 cu.in (2.49 L) |
| Rated Engine Power: 161-200 Hp (120-149 kW) at 5500-6000 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Mitsubishi 6G73 is a 2.5-liter V6 engine produced
from the early 1990s through the late 1990s as part of the broader 6G7 family,
which also included the 3.0-liter 6G72 and the 2.0-liter 6A12. The 6G73 was
developed to occupy a middle ground in the Mitsubishi lineup, offering greater
torque and refinement than the four-cylinder engines found in mid-range sedans
while providing a more compact and fuel-efficient alternative to the larger
3.0-liter V6.
The engine’s 60-degree bank angle was selected for its inherent primary and
secondary balance characteristics, allowing for smooth operation without the
requirement for balance shafts. The 6G73 was offered in two distinct valvetrain
configurations: a single overhead camshaft (SOHC) 24-valve version and a dual
overhead camshaft (DOHC) 24-valve version, each delivering different power
characteristics suited to different vehicle platforms.
The engine found its widest application in Mitsubishi’s own Diamante and Galant
models, as well as in the Chrysler Sebring and Dodge Avenger through the
strategic alliance between Mitsubishi and Chrysler during that period.
The 6G73 engine represents Mitsubishi’s approach to V6 engineering in the 1990s,
prioritizing smooth power delivery and mechanical refinement within a compact
package. The engine’s 60-degree architecture provides excellent inherent
balance, contributing to the low vibration levels that distinguished these
vehicles in their respective segments.
The cast iron cylinder block and aluminum cylinder heads combine durability with
reasonable weight, while the belt-driven valvetrain - whether SOHC or DOHC -
employs hydraulic lash adjusters to eliminate the requirement for routine valve
clearance maintenance. The SOHC variant was calibrated for broad torque delivery
suited to the Chrysler coupes and Mitsubishi sedans aimed at a comfort-oriented
driving experience, while the DOHC variant delivered higher peak power for the
sportier applications.
The engine’s fuel system utilizes Mitsubishi’s ECI-MULTI (Electronic Controlled
Injection) multipoint fuel injection, providing reliable cold starts and
consistent performance across varying operating conditions. The 6G73’s
reputation is mixed: its fundamental mechanical architecture is robust, but it
suffers from age-related issues common to engines of this era, including
hydraulic lifter noise from inadequate oil maintenance, distributor oil seal
leaks, and hardening valve stem seals at higher mileages. The interference
valvetrain design also demands strict adherence to timing belt replacement
intervals, as a belt failure results in catastrophic valve-to-piston contact.
Production Period: 1991-1998.
Engine Code: 6G73.
Configuration: 60° V6.
Displacement: 2,497 cc (152.4 cu.in).
Bore: 83.5 mm (3.29 in).
Stroke: 76.0 mm (2.99 in).
Firing Order: 1-2-3-4-5-6.
Compression Ratio (SOHC): 9.5:1.
Compression Ratio (DOHC): 10.0:1.
Combustion System: Multipoint fuel injection.
Aspiration: Naturally aspirated.
Maximum Engine Speed: 6,500 rpm (SOHC).
Maximum Engine Speed: 7,000 rpm (DOHC).
Power Output (SOHC 24-Valve)
Maximum Power: 161-163 hp (120-122 kW) @ 5,500 rpm.
Maximum Torque: 163 lb-ft (221 Nm) @ 4,500 rpm.
Power Output (DOHC 24-Valve)
Maximum Power: 197-200 hp (147-149 kW) @ 6,000 rpm.
Maximum Torque: 177 lb-ft (240 Nm) @ 5,000 rpm.
The 6G73 cylinder block is manufactured from cast iron
with a 60-degree V-angle, a configuration chosen for its inherent balance
characteristics that reduce vibration without requiring auxiliary balance
shafts. The block features a closed-deck design at the top of the cylinder
bores, contributing to improved head gasket sealing and structural rigidity
under load. The cylinder bores are cast directly into the block and are finished
with a precision-honed surface. Four main bearings support the crankshaft, with
the bearing caps secured using high-tensile steel bolts.
The block incorporates the mounting provisions for the oil pump at the front and
the water pump on the side. Cast-in coolant passages surround each cylinder
bank, while oil galleries are drilled into the block to supply pressurized
lubricant to the crankshaft, connecting rods, and cylinder heads. The engine
mounting points are cast into the block to accommodate various vehicle
platforms, including both transverse and longitudinal orientations depending on
the application.
The cylinder heads are manufactured from cast aluminum
alloy, with separate heads for each cylinder bank. The valvetrain configuration
varies by application: SOHC variants utilize a single camshaft per cylinder head
operating four valves per cylinder through rocker arms, while DOHC variants
employ two camshafts per cylinder head with the valves actuated directly via
bucket-type hydraulic lash adjusters.
Both configurations utilize 24 valves total, with each cylinder served by two
intake valves and two exhaust valves. The intake valves measure approximately
33.0 mm (1.30 in) in diameter, while the exhaust valves measure approximately
28.0 mm (1.10 in). Hydraulic lash adjusters are incorporated into both
valvetrain designs, eliminating the requirement for manual valve clearance
adjustments.
The SOHC heads utilize a camshaft that operates both intake and exhaust valves
through a system of rocker arms and lost-motion springs. The DOHC heads feature
individual camshafts for intake and exhaust, with the camshafts driven by a
timing belt that routes from the crankshaft through an intermediate idler
pulley.
The fuel system utilizes Mitsubishi’s ECI-MULTI
(Electronic Controlled Injection) multipoint fuel injection, with a fuel
injector positioned at each intake port. The system operates at a nominal fuel
pressure of approximately 2.5 bar (36 psi) for SOHC variants and 3.0 bar (44
psi) for DOHC variants. Fuel is delivered from the in-tank fuel pump through a
fuel filter and to a fuel rail mounted to each cylinder head. The injectors are
sequentially fired by the engine control unit based on signals from the
crankshaft position sensor and camshaft position sensor.
A fuel pressure regulator is mounted on the fuel rail, maintaining consistent
pressure by returning excess fuel to the tank. The system incorporates a
cold-start injector on some early variants to provide additional fuel enrichment
during cold-start conditions. The engine control unit manages injector pulse
width based on inputs including engine speed, load, coolant temperature, intake
air temperature, and exhaust oxygen sensor feedback.
The lubrication system employs a wet-sump design with a
gear-type oil pump mounted within the front timing cover, driven directly by the
crankshaft. The pump draws oil from the sump through a screened pickup tube and
delivers it through a full-flow spin-on oil filter mounted on the cylinder
block. The filtered oil is distributed through internal galleries to the
crankshaft main bearings, connecting rod bearings, camshaft bearings, and the
hydraulic lash adjusters.
An oil pressure relief valve is integrated into the oil pump assembly to
maintain consistent pressure and prevent over-pressurization at higher engine
speeds. The hydraulic lash adjusters rely on a consistent supply of clean oil to
maintain proper valvetrain operation; oil contamination or incorrect viscosity
can result in audible lifter noise. Total system capacity, including the filter,
is approximately 4.5 liters (4.8 qt) for most applications, though this varies
slightly depending on the oil pan configuration and vehicle platform.
The cooling system is a pressurized water-cooled design
utilizing a crossflow aluminum radiator with plastic end tanks. A centrifugal
water pump, driven by the timing belt on the front of the engine, circulates
coolant through the cylinder block, cylinder heads, and radiator. The water pump
is a service item replaced in conjunction with the timing belt. A wax-element
thermostat is positioned in the coolant outlet housing, with a nominal opening
temperature of 82°C (180°F) for most applications.
The system incorporates an expansion tank to accommodate coolant expansion
during operation and to facilitate air removal. An electric cooling fan,
controlled by the engine control unit or a dedicated fan relay, provides airflow
across the radiator during low-speed operation and stationary idle. The cooling
system is designed to manage the thermal load of the V6 configuration, with the
two cylinder banks arranged to allow uniform coolant distribution. Coolant
capacity varies by vehicle application but generally ranges from 7.0 to 8.0
liters (7.4 to 8.5 qt).
| Intake and Exhaust Systems |
Intake System: The intake system consists of an air
cleaner housing with a replaceable dry-type filter element, a mass airflow
sensor, and a two-piece intake manifold. The intake manifold is constructed from
aluminum and incorporates a plenum chamber and individual runners to each
cylinder head. The runner length is tuned to optimize torque delivery across the
engine’s operating range. SOHC and DOHC variants utilize different intake
manifold configurations to match their respective power characteristics.
Exhaust System: The exhaust system utilizes a cast iron exhaust manifold on each
cylinder bank, with the manifolds merging into a single exhaust pipe downstream.
The system incorporates one or two oxygen sensors upstream of the catalytic
converter for closed-loop fuel control, with a downstream sensor on later models
for catalyst monitoring.
| Ignition and Electrical System |
Ignition System: The ignition system varies by
application and model year. Early SOHC variants utilize a distributor-based
system with a single ignition coil, with the distributor driven by the rear of
the intake camshaft on the front cylinder bank. DOHC variants and later SOHC
engines utilize a distributorless ignition system with individual ignition coils
mounted near each spark plug or a waste-spark configuration with three coils
serving six cylinders. The spark plugs are accessed through the valve covers.
Electrical System: The engine is equipped with a 12-volt electrical system. The
starter motor is mounted to the transmission bellhousing, engaging with the
flywheel ring gear. The alternator is belt-driven from the crankshaft pulley and
provides charging current for the battery and vehicle electrical loads.
Overall Length: 620 mm (24.4 in).
Overall Width: 650 mm (25.6 in).
Overall Height: 670 mm (26.4 in).
Dry Weight (complete engine): 160-170 kg (353-375 lbs).
Engine Oil: SAE 5W-30 or 10W-30 meeting API SG or
higher classification. Oil Capacity (with filter change): 4.5 L (4.8 qt). Oil
Change Interval: 5,000-7,500 km (3,100-4,700 mi) under normal conditions. Timing
Belt Replacement Interval: 96,000 km (60,000 mi) for interference engine;
failure results in valve damage.
Spark Plug Type: NGK PFR6G-11 or equivalent. Spark Plug Gap: 1.0-1.1 mm
(0.040-0.043 in). Spark Plug Change Interval: 48,000 km (30,000 mi) for copper
plugs; 96,000 km (60,000 mi) for platinum plugs. Coolant Capacity: 7.0-8.0 L
(7.4-8.5 qt) depending on vehicle platform.
Coolant Specification: Ethylene glycol-based antifreeze with corrosion
inhibitors; replace every 2 years or 40,000 km (24,800 mi). Engine Idle Speed:
650-750 rpm.
Connecting Rod Cap Bolts: 40 Nm (30 lb-ft) + 90° to
100° turn
Main Bearing Cap Bolts: 50 Nm (37 lb-ft) + 90° to 100° turn
Cylinder Head Bolts (SOHC): Stage 1: 30 Nm (22 lb-ft)
Cylinder Head Bolts (SOHC): Stage 2: 60 Nm (44 lb-ft) +90°
Cylinder Head Bolts (DOHC): Stage 1: 40 Nm (30 lb-ft)
Cylinder Head Bolts (DOHC): Stage 2: 80 Nm (59 lb-ft) +90°
Camshaft Bearing Caps: 20 Nm (15 lb-ft)
Intake Manifold to Cylinder Head: 20-25 Nm (15-18 lb-ft)
Exhaust Manifold to Cylinder Head: 30-35 Nm (22-26 lb-ft)
Flywheel/Flexplate to Crankshaft: 100 Nm (74 lb-ft)
Spark Plugs: 25 Nm (18 lb-ft)
Timing Belt Tensioner Pulley: 45 Nm (33 lb-ft)
Oil Filter Housing to Block: 30 Nm (22 lb-ft)
Mitsubishi Models:
Mitsubishi Diamante (1992-1996): F17A, F24A, F33A chassis with 6G73 DOHC
24-valve engine.
Mitsubishi Galant (1994-1998): E54A, E64A, E74A chassis with 6G73 DOHC 24-valve
engine (selected markets).
Mitsubishi Eclipse (1995-1999): 6G73 SOHC 24-valve engine utilized in certain
export market variants.
Chrysler Corporation (Mitsubishi Joint Venture):
Chrysler Sebring (1995-1998): JX platform coupe with 6G73 SOHC 24-valve engine.
Dodge Avenger (1995-1998): JX platform coupe with 6G73 SOHC 24-valve engine.
Chrysler Cirrus (1995-1998): Selected export market variants with 6G73 SOHC
24-valve engine.
Other Applications:
Eagle Talon (1995-1998): Selected export market variants with 6G73 SOHC 24-valve
engine through Chrysler distribution channels.
Hyundai (Selected Markets): Limited application of the 6G73 in Hyundai-branded
vehicles during the technical cooperation period with Mitsubishi.
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