Subaru EF12 Specifications
| Engine Model: Subaru EF12 |
| Engine Type: 4-cycle inline 3-cylinder SOHC 9-valve liquid-cooled gasoline |
| Total Displacement: 72.6 cu.in (1.19 L) |
| Rated Engine Power: 69 Hp (51 kW) at 6000 rpm |
| Fuel System Type: Electronic multi-point fuel injection (MPFI/EFI) |
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The Subaru EF12 is a 1.2-liter,
inline-three-cylinder, single overhead camshaft (SOHC), 9-valve,
naturally aspirated gasoline engine. It is a member of Subaru's
"E-series" of inline engines, specifically designed for
front-wheel-drive kei car and subcompact applications in the Japanese
domestic market (JDM) during the 1990s. This compact and lightweight
three-cylinder unit is notable for its unusual valve configuration,
featuring three valves per cylinder (two intake, one exhaust) for a
total of nine valves. The design emphasizes fuel efficiency, low cost,
and adequate power within the constraints of Japanese vehicle
classifications.
Its inline-three layout inherently produces more vibration than an
inline-four, but its compact size and light weight are advantageous for
small vehicles. The EF12 is known for its frugal fuel consumption,
simple mechanical design, and characteristic three-cylinder thrum. While
not powerful, it provides adequate performance for urban commuting in
lightweight vehicles like the Subaru Vivio. It represents a niche,
economy-focused chapter in Subaru's diverse engine history.
Engine Family / Model: Subaru E-series (Inline), Model EF12.
Engine Type: Inline-three cylinder, transversely front-mounted,
four-stroke cycle, water-cooled, naturally aspirated gasoline engine.
Fuel Management: Electronic Multi-Point Fuel Injection (MPFI/EFI).
Valve Configuration: Three valves per cylinder (two intake, one
exhaust), 9-valve total.
Aspiration: Naturally aspirated.
Bore: 78.0 mm / 3.071 inches.
Stroke: 83.0 mm / 3.268 inches.
Displacement: 1,189 cc / 72.6 cubic inches.
Compression Ratio: 9.5 : 1. Firing Order: 1-2-3.
Rotation Direction (from front/timing belt end): Clockwise.
Maximum Power Output (JIS Net): 51 kW (69 Hp) at 6,000 rpm.
Maximum Torque: 98-102 Nm (72-75 lb-ft) at 3,600 rpm. Redline: 6,500
rpm.
Fuel Requirement: Regular unleaded gasoline (91 RON).
Emissions Compliance: Japanese regulations of the early 1990s.
Construction: Cast iron, with a simple, lightweight open-deck design.
The inline-three configuration results in a very short block length,
ideal for transverse mounting in small engine bays.
Cylinder Bores: Integral (parent bore) in the casting. Standard bore
diameter is 78.00 mm (3.071 inches). Crankshaft: Cast nodular iron,
supported by four main bearings. The crankshaft design must account for
the inherent imbalance of a three-cylinder layout.
Main Bearings: Steel-backed, aluminum alloy shell bearings.
Pistons: aluminum alloy with a flat or slightly dished crown designed
for the three-valve combustion chamber. Connecting Rods: Forged steel or
high-strength powder metal.
Balance Shaft: May be equipped with a single balance shaft, driven by
the timing belt or chain, to help counteract the primary vertical
imbalance forces of the three-cylinder design, improving smoothness.
Oil Pan: Stamped steel oil pan.
Construction: aluminum alloy, cross-flow design.
Valve Arrangement: Single Overhead Camshaft (SOHC), driven by a toothed
timing belt. Unique three-valve layout: two intake valves and one larger
exhaust valve per cylinder (9-valve total).
Valvetrain: The single camshaft operates all valves via rocker arms. The
two intake valves for each cylinder are typically actuated by a forked
rocker arm from a single cam lobe, simplifying the design.
Combustion Chamber: Hemispherical or pent-roof type, designed around the
three-valve layout. This design aims to improve airflow and combustion
efficiency over a two-valve head while being cheaper to manufacture than
a four-valve head. Valve Seat Angle: 45 deg.
Valve Diameter: Intake: 27.0 mm (1.063 inches) each. Exhaust: 31.0 mm
(1.220 inches).
Valve Clearance (Cold): Adjustable via screw and locknut on the rocker
arms. Clearance: Intake: 0.15-0.25 mm (0.006-0.010 in). Exhaust:
0.25-0.35 mm (0.010-0.014 in). Specific values must be confirmed per
workshop manual. Camshaft Drive: Toothed rubber timing belt with an
automatic hydraulic or mechanical tensioner and idler pulley.
Injection System: Multi-Point Fuel Injection (MPFI/EFI). Individual
injectors for each cylinder mounted in the intake manifold. Engine
Control Unit (ECU): Subaru-specific digital ECU.
Fuel Injectors: Electromagnetic, top-feed injectors.
Fuel Pressure Regulator: Vacuum-referenced, mounted on the fuel rail.
Throttle Body: Single-bore, cable-operated.
Air Intake: Utilizes an Air Flow Meter (AFM-vane type) or a Manifold
Absolute Pressure (MAP) sensor for load calculation. Idle Air Control
(IAC) Valve: Maintains stable idle speed.
Type: Full-pressure, force-fed wet-sump system.
Oil Pump: Internal gear (trochoid) type, chain-driven from the
crankshaft or directly driven.
Oil Filter: Standard spin-on canister type. Oil Cooler: Not equipped.
Oil Capacity (including filter): 3.2 liters (3.4 US quarts / 2.8
Imperial quarts).
Recommended Oil Grade: API SF/SG or later. Viscosity: SAE 10W-30 or
10W-40.
Operating Oil Pressure: At operating temperature: 294-441 kPa (3.0-4.5
kgf/cm2 / 43-64 psi) at 3,000 rpm.
Type: Pressurized, forced circulation system.
Water Pump: Centrifugal, belt-driven from the crankshaft (likely by the
timing belt itself or an accessory belt). Thermostat: Wax pellet type.
Opening temperature is 82°C (180°F).
Radiator Pressure Cap: 88-108 kPa (0.9-1.1 kgf/cm2 / 13-16 psi).
Coolant Capacity (engine + radiator, approx.): 4.5 liters (4.8 US quarts
/ 4.0 Imperial quarts).
Coolant Recommendation: Ethylene-glycol based antifreeze mixed with
demineralized water (50/50 ratio).
Electrical System: 12-volt DC, negative ground.
Ignition System: Distributor-based electronic ignition (breakerless)
with a single coil, rotor, and spark plug wires. The distributor is
likely driven by the camshaft.
Spark Plugs: Standard nickel. Gap: 0.7-0.8 mm (0.028-0.031 in).
Emission Controls: Basic systems including Exhaust Gas Recirculation
(EGR), Positive Crankcase Ventilation (PCV), and a three-way catalytic
converter.
Transmission: Paired with a 5-speed manual transmission or a 3/4-speed
automatic transaxle in a front-wheel-drive layout.
Length (from front of pulley to rear of block): 450 mm (17.7 inches).
Width (over valve cover): 550 mm (21.7 inches).
Height (from bottom of sump to top of valve cover): 600 mm (23.6
inches).
Dry Weight (engine only, complete): 80-85 kg (176-187 lbs).
Engine Oil and Filter Change Interval: Every 5,000 km (3,100 miles) or 6
months.
Spark Plugs: Replace every 20,000 km (12,400 miles).
Timing Belt: Replace every 100,000 km (62,000 miles) or 5-7 years.
Confirm if interference or non-interference design.
Valve Clearance Adjustment: Check and adjust every 20,000-40,000 km
(12,400-24,850 miles). Vital for smooth operation and performance.
Accessory Drive Belts: Inspect and adjust tension regularly.
Coolant Replacement: Every 2 years or 40,000 km (24,850 miles).
Fuel Filter: Replace every 40,000 km (24,850 miles).
Air Filter: Replace every 20,000 km (12,400 miles).
Distributor Cap and Rotor: Inspect and replace as part of a standard
tune-up every 40,000 km.
Cylinder Head Bolts: Multi-stage torque procedure. Step 1: Tighten all
bolts in sequence to 30 Nm (22 lb-ft). Step 2: Tighten all bolts in
sequence to 60 Nm (44 lb-ft). Always follow the specific factory
sequence.
Main Bearing Cap Bolts: 54-59 Nm (40-44 lb-ft).
Connecting Rod Cap Bolts: 30-35 Nm (22-26 lb-ft).
Flywheel to Crankshaft Bolts: 60-70 Nm (44-52 lb-ft).
Crankshaft Pulley Bolt: 110-130 Nm (81-96 lb-ft).
Camshaft Sprocket Bolt: 50-60 Nm (37-44 lb-ft).
Spark Plugs: 18-22 Nm (13-16 lb-ft).
Oil Pan Bolts: 8-12 Nm (6-9 lb-ft).
Rocker Cover Bolts: 8-10 Nm (6-7 lb-ft).
Intake Manifold Bolts/Nuts: 18-22 Nm (13-16 lb-ft).
Exhaust Manifold Nuts: 30-35 Nm (22-26 lb-ft).
Balance Shaft Sprocket Bolt (if equipped): 40-50 Nm (30-37 lb-ft).
The Subaru EF12 1.2L inline-three engine had a very limited and specific
application in the Japanese Domestic Market: Subaru Vivio (1992-1998):
This is the confirmed and primary application. The EF12 engine was used
in certain higher-trim or non-kei versions of the Vivio, where the
vehicle was registered under a larger class than the standard 660cc kei
car classification. It provided more power than the standard EN07 660cc
engine. It was notably used in some performance-oriented models like the
Vivio RX-R.
Information on the EF12 as a three-cylinder is less common than its
four-cylinder counterpart. Its use was highly specific to certain Vivio
models that exceeded kei car displacement limits. Most references to the
EF12 describe a four-cylinder engine; this three-cylinder variant
appears to be a specific, lower-production version for a niche market
segment. It is a rare engine by global standards.
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