Mitsubishi 6A12 Specifications
| Engine Model: Mitsubishi 6A12 |
| Engine Type: 4-cycle 6-cylinder V-block DOHC or SOHC liquid-cooled gasoline |
| Total Displacement: 122 cu.in (1.99 L) |
| Rated Engine Power: 145-175 Hp (108-130 kW) at 6000-7000 rpm |
| Fuel System Type: Multi-point fuel injection |
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The Mitsubishi 6A12 is a 2.0-liter V6 engine produced
by Mitsubishi Motors from 1992 through the early 2000s, distinguished as one of
the smallest production V6 engines ever manufactured. This compact six-cylinder
powerplant was engineered to deliver the smoothness and refinement of a V6
configuration within the dimensional constraints of the 2.0-liter displacement
class, a segment traditionally dominated by inline-four engines.
The 6A12 formed part of Mitsubishi’s broader 6A engine family and appeared in
two distinct naturally aspirated valvetrain configurations: a single overhead
camshaft (SOHC) variant prioritizing low-end torque and manufacturing economy,
and a double overhead camshaft (DOHC) variant optimized for higher output and
elevated engine speeds.
The fundamental architecture of the 6A12 centers on a 60° V6 layout, a
configuration selected to minimize overall engine width while maintaining
inherent primary balance without requiring additional balancer shafts. The
compact dimensions of this powerplant allowed installation in vehicle platforms
originally designed for four-cylinder engines, contributing to the proliferation
of V6-powered variants across Mitsubishi’s mid-size sedan and coupe lineup. Both
SOHC and DOHC variants utilized the same 78.4 mm bore and 69.0 mm stroke,
yielding a displacement of 1,998 cc.
The SOHC configuration produced 145 to 150 hp (108 to 112 kW) at 6,000 rpm with
181 Nm (134 lb-ft) of torque at 4,500 rpm, operating at a compression ratio of
9.5:1. The DOHC variant delivered 170 to 175 hp (127 to 130 kW) at 7,000 rpm
with 191 Nm (141 lb-ft) of torque at 4,000 rpm, utilizing a compression ratio of
10.0:1. Both configurations employed hydraulic lash adjusters (HLA), eliminating
the need for periodic valve clearance maintenance. The engine utilized a
belt-driven valvetrain with a replacement interval of 100,000 km (60,000 mi),
and the interference design necessitated strict adherence to this schedule to
prevent valve-to-piston contact in the event of belt failure.
The 6A12 operates on a four-stroke gasoline cycle with multi-point electronic
fuel injection. The engine utilizes a 60° V6 configuration with the cylinder
banks arranged to minimize overall width while maintaining engine balance.
Engine Type: 60° V6, water-cooled, 4-stroke, naturally aspirated gasoline.
Displacement: 1,998 cc (122 cu.in).
Bore: 78.4 mm (3.09 in).
Stroke: 69.0 mm (2.72 in).
Compression Ratio (SOHC): 9.5:1.
Compression Ratio (DOHC): 10.0:1.
Firing Order: 1-2-3-4-5-6.
Idle Speed: 700-750 rpm, electronically controlled.
Maximum Engine Speed (SOHC): 6,500 rpm with fuel cut-off at 6,800 rpm.
Maximum Engine Speed (DOHC): 7,200 rpm with fuel cut-off at 7,500 rpm.
Maximum Power (SOHC): 108-112 kW (145-150 hp) @ 6,000 rpm.
Maximum Power (DOHC): 127-130 kW (170-175 hp) @ 7,000 rpm.
Maximum Torque (SOHC): 181 Nm (134 lb-ft) @ 4,500 rpm.
Maximum Torque (DOHC): 191 Nm (141 lb-ft) @ 4,000 rpm.
Fuel System: ECI-MULTI (Electronic Control Injection) with sequential port
injection.
Aspiration: Naturally aspirated.
The cylinder block is constructed from cast iron with a
60° bank angle between the two cylinder banks. This configuration places the
left and right cylinder banks at a narrower angle than conventional 90° V6
designs, reducing overall engine width and allowing installation in compact
engine bays originally designed for four-cylinder powerplants. The block
features a deep-skirt design that extends below the crankshaft centerline,
contributing to structural rigidity and reducing vibration transmission to the
vehicle chassis.
The cylinder bores are integrally cast into the block with no replaceable
liners. Each bore is induction-hardened to provide a durable wear surface for
the piston rings. The water jackets surrounding each cylinder bank are separate
but interconnected through passages in the block casting to ensure uniform
cooling across all six cylinders.
Main bearing caps are manufactured from nodular cast iron and are secured with
four bolts each - two vertical bolts through the cap and two horizontal
cross-bolts through the lower crankcase structure on select variants. The
cross-bolted main bearing configuration provides additional crankshaft support
under high engine speeds and sustained load conditions.
Crankshaft: Forged steel with four main bearings, fully counter-weighted with
four counterweights. The crankshaft features induction-hardened bearing surfaces
and is dynamically balanced to minimize vibration inherent to the 60° V6
configuration.
Main Bearing Journal Diameter: 55.0 mm (2.17 in).
Connecting Rod Journal Diameter: 48.0 mm (1.89 in).
Connecting Rods: Forged steel with a fracture-split cap design on later
production variants; earlier variants utilized machined mating surfaces with
locating dowels. Piston Material: Cast aluminum alloy with a low-friction skirt
coating. Piston Cooling: Oil jets are not present in this naturally aspirated
engine; piston cooling is accomplished through oil splash from the connecting
rod bearings.
The 6A12 utilizes two separate cylinder heads, one for
each bank of cylinders, each manufactured from aluminum alloy. The SOHC and DOHC
variants employ distinct cylinder head castings with different valvetrain
configurations.
SOHC Cylinder Head: Each bank incorporates a single belt-driven camshaft
operating two valves per cylinder (12 valves total) through roller-type rocker
arms. The rocker arms are mounted on a shaft running the length of each head.
Hydraulic lash adjusters (HLA) are integrated into the rocker arm pivot points,
automatically maintaining zero valve clearance throughout the engine’s service
life.
DOHC Cylinder Head: Each bank incorporates two belt-driven camshafts - one
intake and one exhaust - operating four valves per cylinder (24 valves total).
The camshafts act directly on inverted bucket-type tappets. Hydraulic lash
adjusters (HLA) are integrated into the tappets, eliminating the need for valve
clearance adjustment.
Intake Valve Diameter (SOHC): 34.0 mm (1.34 in).
Exhaust Valve Diameter (SOHC): 30.0 mm (1.18 in).
Intake Valve Diameter (DOHC): 33.0 mm (1.30 in).
Exhaust Valve Diameter (DOHC): 28.0 mm (1.10 in).
Valve Lift (SOHC Intake): 8.5 mm (0.335 in).
Valve Lift (SOHC Exhaust): 8.0 mm (0.315 in).
Valve Lift (DOHC Intake): 9.5 mm (0.374 in).
Valve Lift (DOHC Exhaust): 9.0 mm (0.354 in).
Valve Seat Material: Sintered steel alloy with induction-hardened contact
surfaces.
Valve Spring Material: High-tensile steel with a conventional cylindrical
design.
Camshaft Drive: Belt-driven system utilizing a single toothed timing belt. The
belt drives the front cylinder bank camshaft(s) directly from the crankshaft
sprocket, with a secondary belt or gear transferring drive to the rear bank
camshaft(s). An automatic spring-loaded tensioner maintains belt tension.
The fuel system utilizes ECI-MULTI, Mitsubishi’s
electronic multi-point injection system. This sequential port injection system
delivers fuel through injectors positioned in the intake manifold runners,
immediately upstream of the intake valves.
Fuel Injectors: Multi-hole solenoid-type injectors, each delivering fuel to an
individual cylinder. The injectors are mounted in the intake manifold and are
electrically actuated by the engine control unit. Fuel Pressure: 280-320 kPa
(41-46 psi) regulated by a vacuum-referenced pressure regulator mounted on the
fuel rail.
Fuel Rail: Aluminum rail shared across each cylinder bank, incorporating the
pressure regulator and a fuel damper to reduce pressure pulsations. Throttle
Body: Cable-actuated throttle body with an integrated idle air control (IAC)
valve and throttle position sensor. Fuel Requirement: Minimum octane rating of
91 RON (87 AKI) for SOHC variants; 95 RON (91 AKI) recommended for DOHC
variants.
Intake Manifold: Cast aluminum or composite resin construction depending on
variant. The intake manifold features a dual-runner design in DOHC applications,
with a butterfly valve that alters effective runner length based on engine speed
to optimize torque characteristics.
The lubrication system is a fully pressurized wet-sump
design with a gear-type oil pump mounted on the front of the engine. The pump is
driven directly by the crankshaft through the timing belt system and
incorporates a pressure relief valve.
Oil Pump Type: Gear-type pump with integrated pressure relief valve. Recommended
Oil Viscosity: 10W-30 conventional or 5W-40 fully synthetic, meeting API SG, SH,
SJ, or higher specifications. Oil Capacity (including filter): 4.0-4.3 liters
(4.2-4.5 qt) depending on oil pan configuration.
Oil Pressure (at idle, warm): 70-100 kPa (10-15 psi).
Oil Pressure (at 3,000 rpm, warm): 300-400 kPa (44-58 psi).
Oil Filter Type: Spin-on full-flow filter with integral bypass valve and
anti-drainback valve.
Oil Pan: Stamped steel with integrated baffling.
The cooling system is a pressurized, thermostatically
controlled circuit utilizing a belt-driven centrifugal water pump. The water
pump is driven by the timing belt in this engine configuration, necessitating
replacement during timing belt service.
Water Pump Type: Centrifugal with a mechanical seal, mounted to the front of the
cylinder block and driven by the timing belt. Coolant Type: Ethylene-glycol
based antifreeze meeting Mitsubishi specification, phosphate and silicate-free
formulation. Coolant Capacity (engine and radiator): 7.0-7.5 liters (7.4-7.9
qt).
Thermostat: Wax-type thermostat with an opening temperature of 82 °C (180 °F)
and a full-open temperature of 95 °C (203 °F). Radiator: Cross-flow aluminum
radiator with plastic tanks. Cooling Fan: Electric fan(s) controlled by engine
coolant temperature sensor and air conditioning system demand.
Distributor-based ignition on early SOHC variants;
distributorless ignition system (DIS) with coil-on-plug or coil-pack
configuration on later SOHC and DOHC variants. The ignition system utilizes a
crankshaft position sensor and camshaft position sensors for timing
synchronization.
Spark Plugs: NGK PFR6G-11 platinum or equivalent.
Spark Plug Gap: 1.0-1.1 mm (0.039-0.043 in).
Timing Drive: Belt-driven system with a toothed rubber
timing belt reinforced with fiberglass cords. The belt drives the water pump,
the front cylinder bank camshaft(s), and an intermediate shaft that drives the
rear cylinder bank camshaft(s) through a secondary belt. The belt must be
replaced at specified intervals. This is an interference engine; timing belt
failure results in valve-to-piston contact requiring extensive engine repair.
Accessory Drive: Single V-ribbed serpentine belt driving the alternator, power
steering pump, and air conditioning compressor. A manual adjustment or
spring-loaded automatic tensioner maintains belt tension.
Engine Management System: Mitsubishi engine control unit (ECU) with integrated
fuel injection control, ignition timing control, and diagnostic functions. DOHC
variants utilize a more advanced ECU with higher-resolution mapping for elevated
engine speeds.
Exhaust System: Dual exhaust manifolds, one per cylinder bank, constructed from
cast iron. The exhaust system incorporates a crossover pipe combining both banks
before entering the catalytic converter.
Emissions Compliance: Meets emissions standards applicable at time of
manufacture, including Euro 2 for European market vehicles.
Overall Length: 650 mm (25.6 in)
Overall Width: 620 mm (24.4 in)
Overall Height: 680 mm (26.8 in)
Dry Weight (SOHC): 145 kg (320 lb)
Dry Weight (DOHC): 150 kg (331 lb)
Engine Oil and Filter Change: 5,000 km (3,000 mi) or 6
months for conventional oil; 10,000 km (6,000 mi) or 12 months for fully
synthetic oil. Timing Belt Replacement: 100,000 km (60,000 mi) or 5 years,
whichever occurs first. Failure to replace the belt within this interval risks
belt fracture and consequent valve damage due to the interference design.
Water Pump Replacement: Replaced concurrently with timing belt due to water pump
drive by the timing belt. Spark Plug Replacement: 100,000 km (60,000 mi) for
platinum plugs. Engine Air Filter Element: Replace every 20,000 km (12,000 mi)
or when visibly contaminated. Coolant Replacement: 40,000 km (24,000 mi) or 2
years.
Drive Belt Inspection: Every 10,000 km (6,000 mi) for cracks, fraying, glazing,
and proper tension. Drive Belt Replacement: 40,000 km (24,000 mi) or 3 years.
Valve Clearance: Hydraulic lash adjusters (HLA) eliminate the need for valve
clearance inspection or adjustment throughout the engine’s service life. Fuel
Filter Replacement: 40,000 km (24,000 mi) or 2 years.
Cylinder Head Bolts (SOHC and DOHC), Step 1: 30 Nm (22
lb-ft)
Cylinder Head Bolts (SOHC and DOHC), Step 2: 60 Nm (44 lb-ft) + 90° turn
Main Bearing Cap Bolts: 50 Nm (37 lb-ft) + 90° turn
Connecting Rod Cap Bolts: 35 Nm (26 lb-ft) + 90° turn
Camshaft Bearing Caps (DOHC): 20 Nm (15 lb-ft)
Camshaft Sprocket Bolts: 80 Nm (59 lb-ft)
Intake Manifold to Cylinder Head: 20 Nm (15 lb-ft)
Exhaust Manifold to Cylinder Head: 30 Nm (22 lb-ft)
Water Pump Mounting Bolts: 20 Nm (15 lb-ft)
Oil Pan Bolts: 15 Nm (11 lb-ft)
Valve Cover Bolts: 10 Nm (7 lb-ft)
Spark Plugs: 25 Nm (18 lb-ft)
Crankshaft Pulley Bolt: 200 Nm (148 lb-ft)
Flywheel / Flexplate Bolts: 100 Nm (74 lb-ft)
Engine Mount Brackets to Block: 45 Nm (33 lb-ft)
The 6A12 engine was installed across a range of
Mitsubishi passenger car platforms from 1992 through the early 2000s, serving as
the mid-range V6 option below the larger 2.5-liter 6A13 and 3.0-liter 6G72
engines.
Mitsubishi Galant (E53A, E54A, E64A, E74A, E84A generations, 1992-2003): The
6A12 was widely utilized in the Galant mid-size sedan across global markets. The
SOHC variant appeared in entry-level V6 configurations, while the DOHC variant
equipped higher-specification Galant VR and Viento models in various export
markets.
Mitsubishi FTO (DE3A generation, 1994-2000): The DOHC 6A12 served as the
powerplant for the FTO GR trim level, positioned below the MIVEC-equipped FTO
GPX. This application utilized a transverse mounting configuration tuned for the
sport coupe’s performance characteristics.
Mitsubishi Diamante (F1, F2 generations, 1992-1996): The 6A12 appeared in select
markets as the base V6 engine in the Diamante luxury sedan, primarily in Japan
and Southeast Asian markets where 2.0-liter displacement offered tax advantages.
Mitsubishi Eterna (1992-1998): The Eterna mid-size sedan, a platform companion
to the Galant, received both SOHC and DOHC variants of the 6A12 across its model
range.
Mitsubishi Emeraude (1992-1996): This hardtop sedan variant of the Galant
platform utilized the 6A12 in both naturally aspirated configurations for the
Japanese domestic market.
Mitsubishi Legnum (E54A, E64A generations, 1996-2002): The Legnum station wagon,
a Galant-based model, received the 6A12 as the entry-level V6 engine option in
the Japanese domestic market.
Mitsubishi RVR / Space Wagon (N3 generation, select markets): Certain export
market variants of the compact MPV received the SOHC 6A12 as a higher-output
option above the base four-cylinder engine.
Mitsubishi Delica (L400 generation, select markets): Some export market variants
of the Delica van utilized the SOHC 6A12 in passenger-oriented configurations
where V6 refinement was prioritized over the larger diesel engine options.
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