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Mitsubishi 3A92 Specifications
| Engine Model: Mitsubishi 3A92 |
| Engine Type: 4-cycle inline 3-cylinder DOHC 12-valve liquid-cooled gasoline |
| Total Displacement: 72.8 cu.in (1.19 L) |
| Rated Engine Power: 76-81 Hp (57-60 kW) at 6000 rpm |
| Fuel System Type: Sequential multi-point electronic fuel injection |
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| General Technical Data |
The Mitsubishi 3A92 engine is a 1.2-liter inline three-cylinder, four-stroke, naturally aspirated gasoline engine that forms part of the 3A9 family of lightweight, efficient small-displacement powerplants. Introduced in 2012 as the successor to the 3A90 and smaller 3A91 engines, the 3A92 was designed primarily for compact cars such as the Mitsubishi Mirage, Space Star, and Attrage, as well as for several global-market vehicles developed in cooperation with Nissan and Renault.
The engine emphasizes low fuel consumption,
reduced frictional losses, and compact construction, while maintaining
Mitsubishi’s standards of reliability and simplicity of service. It
employs an aluminum alloy block and head, a dual overhead camshaft
configuration, and Mitsubishi Innovative Valve timing Electronic Control
system (MIVEC) on the intake camshaft for improved torque and
efficiency.
Developed under strict Euro 4 and later Euro 5/6 emission standards, the
3A92 represents a balance between lightweight design and durability. The
early Euro 4 version prioritized affordability and minimal emissions
equipment, while the updated Euro 5/6 variants introduced refinements in
combustion chamber design, improved catalytic converter systems, and
recalibrated ECU mapping for lower CO2 output and improved drivability.
With its 1,193 cc of displacement and three-cylinder configuration, the
engine offers an ideal compromise between performance and efficiency for
small, urban-oriented vehicles.
The Mitsubishi 3A92 is a three-cylinder inline gasoline engine with a
total displacement of 1,193 cc (72.8 cubic inches). The bore and stroke
are 75.0 mm (2.95 inches) and 90.0 mm (3.54 inches) respectively, giving
the engine a long-stroke geometry that favors low-end torque and fuel
efficiency. The compression ratio is 10.5:1 for the Euro 4 version and
slightly increased to 11.0:1 for the Euro 5/6 version due to refined
combustion design and advanced knock control.
The engine block is made of die-cast aluminum
alloy with cast-iron cylinder liners inserted for durability and wear
resistance. The cylinder head is also aluminum alloy, using a cross-flow
layout with dual overhead camshafts operating four valves per cylinder,
totaling twelve valves.
The firing order is 1–2–3, and the crankshaft rotates clockwise when
viewed from the flywheel end. It is supported by four main bearings for
smooth operation, and the balance of reciprocating masses is optimized
through the use of an integrated balancer shaft assembly driven by gears
from the crankshaft to minimize secondary vibration inherent in
three-cylinder designs.
The pistons are lightweight aluminum alloy with
graphite-coated skirts and employ full-floating pins for minimal
friction. The connecting rods are forged steel, and the crankshaft is
made from induction-hardened forged steel for strength and longevity.
Power and torque output vary depending on emissions specification and
ECU calibration. The Euro 4 version produces approximately 59 kW (80 Hp,
79 bhp, 59 kW) at 6000 rpm and 106 Nm (78 lb-ft) of torque at 4000 rpm.
The later Euro 5 and Euro 6 variants deliver 57 to 60 kW (77 to 82 PS,
76 to 81 bhp) at 6000 rpm and 100 to 106 Nm (74 to 78 lb-ft) at 4000
rpm, reflecting tuning differences for improved fuel economy and reduced
emissions.
The redline is 6500 rpm with a fuel cut-off at approximately 6700 rpm. Idle speed is electronically controlled between 700 and 750 rpm. The engine complies with Euro 4 (early) and Euro 5/6 (later) emission standards through catalytic aftertreatment and precise fuel and ignition control.
| Fuel System |
The Mitsubishi 3A92 employs an electronically controlled sequential multi-point fuel injection system. Each cylinder is served by an injector located in the intake port near the valve, ensuring even fuel distribution and excellent atomization.
The injectors are solenoid-actuated and controlled by the engine control unit (ECU) based on input from sensors including the mass airflow sensor (MAF), manifold absolute pressure (MAP) sensor, oxygen sensors, throttle position sensor, coolant temperature sensor, and crankshaft/camshaft position sensors.
Fuel is supplied from an in-tank electric pump through a fuel line and
fuel rail maintained at a pressure of approximately 320 kPa (46 psi) by
a regulator integrated into the fuel module. Excess fuel is returned
internally to the tank in a returnless system to minimize vapor
emissions.
The fuel filter is integral with the pump module and designed for the
service life of the vehicle. Recommended fuel is unleaded gasoline with
a minimum octane rating of 95 RON (91 AKI). The Euro 5/6 versions use a
fine-atomization injector design and optimized spray pattern for more
complete combustion and reduced particulate emissions.
Cold-start enrichment and idle stability are controlled electronically via closed-loop lambda feedback from the upstream oxygen sensor. The system is OBD-II compliant and equipped with downstream catalytic converter monitoring for emission diagnostics.
| Lubrication System |
The lubrication system is a fully pressurized wet-sump design employing a trochoid-type oil pump driven by the crankshaft. The oil is drawn through a strainer and delivered to a full-flow paper-element oil filter mounted on the front of the block, from where it is distributed to the main oil gallery feeding the crankshaft, connecting rod journals, camshafts, and valve train components.
Oil jets are installed beneath each piston to spray cooling oil onto the piston undersides, reducing thermal stress and preventing detonation. Normal oil pressure is approximately 300 to 400 kPa (43 to 58 psi) at 3000 rpm and about 100 kPa (15 psi) at idle. Oil capacity, including the filter, is approximately 3.0 liters (3.2 US quarts, 2.6 Imperial quarts).
Recommended oil viscosity is SAE 0W-20 or 5W-30 meeting API SN or higher classification. The crankcase ventilation system uses a positive crankcase ventilation (PCV) valve integrated into the valve cover, ensuring minimal hydrocarbon emission and stable idle quality.
| Cooling System |
The engine is cooled by a pressurized, liquid-based cooling system. A belt-driven centrifugal water pump circulates coolant through the cylinder block, head, radiator, and heater core. The thermostat begins to open at approximately 82 C (180°F) and is fully open by 95°C (203°F).
A cross-flow aluminum radiator with a single or dual electric fan (depending on application) maintains proper operating temperature. System pressure is maintained at around 90 kPa (13 psi) via a spring-loaded radiator cap. The coolant capacity is about 4.5 liters (4.8 US quarts, 4.0 Imperial quarts).
The coolant mixture should consist of a 50/50 blend of ethylene glycol-based antifreeze and distilled water, providing freezing protection down to –35°C (–31°F). The cooling circuit also includes a temperature sensor providing feedback to the ECU and dashboard gauge, and a bypass circuit ensuring even warm-up and temperature stability.
| Intake and Exhaust Systems |
The 3A92 features a lightweight plastic intake manifold designed for low heat absorption and tuned for mid-range torque. The throttle body is electronically controlled (ETCS-i) to ensure smooth response and integration with the idle speed control and traction control systems.
The air intake system includes a resonator to suppress induction noise and a replaceable dry paper air filter element. The exhaust manifold is cast stainless steel and integrates with a close-coupled three-way catalytic converter to achieve rapid light-off after cold start.
The Euro 5/6 variants include a secondary oxygen sensor downstream of the catalyst for closed-loop monitoring and improved emission compliance. Exhaust gas recirculation (EGR) is used on later versions to reduce NOx emissions, controlled via an electronically actuated valve monitored by the ECU.
| Ignition and Electrical System |
The ignition system is a coil-on-plug design using three individual ignition coils mounted directly above the spark plugs. Each coil is controlled independently by the ECU, allowing precise spark timing and dwell control. The system uses iridium-tipped spark plugs gapped at 1.0 millimeter (0.039 inch). Spark plug service interval is 100,000 km (62,000 miles).
The alternator is rated at 85 amperes, and the 12-volt electrical system is grounded via multiple chassis points to ensure reliable operation of electronic controls. The starter motor is a reduction-gear type drawing approximately 1.0 kilowatt during operation. The Euro 5/6 versions introduced revised ECU software with knock detection and adaptive learning ignition control for varying fuel qualities.
| Valve Timing and Drive Mechanism |
The 3A92 engine employs a chain-driven dual overhead camshaft valvetrain. A single-row roller timing chain connects the crankshaft to both camshafts via an intermediate sprocket. An automatic hydraulic tensioner maintains proper chain tension and eliminates the need for periodic adjustment.
The intake camshaft is equipped with Mitsubishi’s MIVEC system, which hydraulically alters cam phasing to optimize torque and fuel economy across different engine speeds. The system can vary valve timing by approximately 30 degrees of crankshaft rotation. Valve lifters are solid bucket type, and valve clearance inspection is recommended every 80,000 to 100,000 km (50,000 to 62,000 miles).
| Other Systems |
The engine includes a closed positive crankcase ventilation (PCV) system, an evaporative emission control (EVAP) system, and an electronically controlled throttle body with integrated idle control. The ECU monitors numerous sensors to maintain optimal performance and emission compliance, including oxygen, knock, throttle position, coolant temperature, and camshaft position sensors.
Later Euro 5/6 versions add an exhaust gas recirculation (EGR) valve with position feedback and secondary air injection for faster catalytic converter light-off. The engine complies with OBD-II diagnostic standards, storing fault codes retrievable through standard scan tools. Electrical connectors are weather-sealed and gold-plated for corrosion resistance.
| Dimensions and Weight |
The Mitsubishi 3A92 engine measures approximately 590 mm (23.2 inches) in length, 620 mm (24.4 inches) in width, and 670 mm (26.4 inches) in height. The dry weight of the engine assembly is about 85 kg (187 lbs), making it one of the lightest engines in its class. This compact size and low weight contribute significantly to the Mirage’s overall efficiency and balance. Engine mounting uses three main rubber-isolated mounts designed to minimize vibration transmission, supplemented by a torque-rod mount to control fore-aft motion.
| Maintenance Data |
Recommended engine oil and filter replacement interval is every 10,000 km (6,000 miles) or annually, whichever occurs first. Under severe driving conditions, oil changes should occur every 5,000 km (3,000 miles). Air filter replacement is recommended every 20,000 km (12,000 miles), or sooner in dusty conditions. Spark plug inspection is suggested at 60,000 km (37,000 miles), with replacement at 100,000 km (62,000 miles).
The coolant should be replaced every 160,000 km (100,000 miles) or every
five years, whichever comes first. Valve clearance inspection should be
carried out every 100,000 km (62,000 miles). Drive belt inspection is
recommended at 40,000 km (25,000 miles) and replacement at 100,000 km
(62,000 miles). The timing chain is designed for the life of the engine
but should be checked for elongation or tensioner wear beyond 200,000 km
(124,000 miles).
Compression pressure for each cylinder when new is approximately 1,300
kPa (189 psi) at 300 rpm, with a minimum allowable limit of 1,000 kPa
(145 psi). The maximum difference between cylinders should not exceed
100 kPa (15 psi). Idle speed is controlled automatically by the ECU,
typically 700 ± 50 rpm. Standard spark plug tightening torque is 20 Nm
(15 lb-ft). The oil drain plug torque is 40 Nm (30 lb-ft).
| Tightening Torques |
Cylinder head bolts: tighten in stages - first 25 Nm (18 lb-ft), then 60
Nm (44 lb-ft), followed by a 90-degree turn.
Main bearing cap bolts: 45 Nm (33 lb-ft) plus 90 degrees.
Connecting rod bolts: 30 Nm (22 lb-ft) plus 90 degrees.
Camshaft bearing cap bolts: 10 Nm (7 lb-ft).
Crankshaft pulley bolt: 160 Nm (118 lb-ft).
Flywheel bolts: 80 Nm (59 lb-ft).
Spark plugs: 20 Nm (15 lb-ft).
Oil drain plug: 40 Nm (30 lb-ft).
Intake manifold bolts: 25 Nm (18 lb-ft).
Exhaust manifold nuts: 35 Nm (26 lb-ft).
Engine mount bolts: 60 Nm (44 lb-ft).
Valve cover bolts: 8 Nm (6 lb-ft).
| Vehicle Applications |
The Mitsubishi 3A92 engine is used widely in compact passenger vehicles
and city cars where efficiency, low emissions, and low operating cost
are priorities.
Major applications include:
– Mitsubishi Mirage / Space Star (2012–present, global markets)
– Mitsubishi Attrage / Mirage G4 (2013–present)
– Mitsubishi Colt (select markets)
– Nissan Micra (certain joint-venture models)
– Renault Clio (Asia and South America variants)
– Smart Forfour (selected co-developed markets)
Euro 4 versions appeared mainly in early Mirage and Colt models from
2012–2014, while Euro 5/6 versions equipped later models from 2015
onward with updated emission systems and ECU calibration. The engine
continues to be produced for emerging markets due to its
cost-effectiveness and proven reliability.
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