Subaru EG33 Specifications
| Engine Model: Subaru EG33 |
| Engine Type: 4-cycle 6-cylinder DOHC 24-valve liquid-cooled gasoline |
| Total Displacement: 202.5 cu.in (3.32 L) |
| Rated Engine Power: 215-234 Hp (160-172 kW) at 5400 rpm |
| Fuel System Type: Sequential multi-point electronic fuel injection (MPFI) |
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The Subaru EG33 is a 3.3-liter,
horizontally-opposed (flat-six), dual overhead camshaft (DOHC),
24-valve, naturally aspirated gasoline engine. It is Subaru's sole
production flat-six engine, developed in the early 1990s as a flagship
powerplant for luxury and performance applications, most notably the
Subaru SVX sports coupe. Based on an extended version of the EJ-series
flat-four block, the EG33 combines the inherent smoothness and balance
of a six-cylinder boxer layout with Subaru's signature low center of
gravity. It features a dual overhead camshaft design with four valves
per cylinder, sequential multi-port fuel injection, and a variable
intake manifold system.
The engine is renowned for its exceptionally silky, linear power
delivery, turbine-like smoothness even at high RPM, and a distinctive,
refined exhaust note. While not tuned for extreme Hp, it delivers
abundant torque across a wide rev range, providing effortless
performance. The EG33 is celebrated for its robust construction,
mechanical refinement, and reliability when properly maintained. It
represents a unique and ambitious high point in Subaru's engineering
history, showcasing their ability to create a world-class, sophisticated
six-cylinder engine.
Engine Family / Model: Subaru EG series (Flat-Six), Model EG33.
Engine Type: Horizontally-opposed six-cylinder (flat-six, boxer),
longitudinally front-mounted, four-stroke cycle, water-cooled, naturally
aspirated gasoline engine.
Fuel Management: Sequential Multi-Point Fuel Injection (MPFI).
Aspiration: Naturally aspirated.
Bore: 96.9 mm / 3.815 inches.
Stroke: 75.0 mm / 2.953 inches.
Displacement: 3,318 cc / 202.5 cubic inches. Compression Ratio: 10.1 :
1.
Firing Order: 1-6-3-2-5-4. (Cylinder numbering: Left bank 1-3-5; Right
bank 2-4-6. Front cylinders are 1 and 2). Rotation Direction (from
front/crank pulley): Clockwise.
Maximum Power Output (JIS Net): 172 kW (234 Hp) at 5,400 rpm
(Japanese-spec). US-spec was typically rated at 160 kW (215 hp) at 5400
rpm.
Maximum Torque: 309 Nm (228 lb-ft) at 4,400 rpm. Redline: 6,500 rpm.
Fuel Requirement: Premium unleaded gasoline (95 RON / 91 AKI minimum, 98
RON recommended).
Emissions Compliance: Varied by market (e.g., US OBD-I, Japanese
regulations).
Construction: Cast aluminum alloy with a semi-closed deck design.
Essentially an EJ-series block extended by two cylinders, resulting in a
very long, rigid casting. The split-case design is retained for
assembly. Cylinder Bores: Cast-in iron liners (dry liners) pressed into
the aluminum block.
Crankshaft: Forged steel, supported by seven main bearings. The flat-six
layout uses a specific crankshaft with crankpins arranged at 120-degree
intervals, providing perfect primary and secondary balance without the
need for balance shafts.
Main Bearings: Steel-backed, aluminum alloy shell bearings.
Pistons: Cast aluminum alloy with a dished crown. Features two
compression rings and one oil control ring. Connecting Rods: Forged
steel, I-beam design.
Balance: Inherently balanced due to the 120-degree crankpin offset and
opposed piston movement, resulting in exceptional smoothness.
Construction: aluminum alloy, one per bank. Based on the DOHC design
from contemporary EJ20 engines but scaled.
Valve Arrangement: Dual Overhead Camshafts (DOHC) per bank (total of
four camshafts), driven by a timing belt system. Four valves per
cylinder (24-valve total).
Valvetrain: Camshafts act directly on buckets with shims for valve
clearance adjustment. No rocker arms. Combustion Chamber: Pent-roof
design with centrally located spark plug.
Valve Seat Angle: 45 deg. Valve Diameter: Intake: 36.0 mm (1.417
inches). Exhaust: 31.0 mm (1.220 inches). Valve Springs: Single coil
springs.
Valve Clearance (Cold): Adjusted by replacing shims located on top of
the bucket followers. Clearance: Intake: 0.20-0.30 mm (0.008-0.012 in).
Exhaust: 0.25-0.35 mm (0.010-0.014 in). Requires camshaft removal for
adjustment. Camshaft Drive: Single, long toothed rubber timing belt
driving all four camshafts and the water pump. Utilizes automatic
hydraulic tensioners and idler pulleys.
Injection System: Sequential Multi-Point Fuel Injection (MPFI). Separate
injectors for each cylinder.
Engine Control Unit (ECU): Subaru-specific digital ECU (e.g., Hitachi).
Controls fuel, ignition, and the variable intake system. Fuel Injectors:
Electromagnetic, top-feed injectors.
Fuel Pressure Regulator: Vacuum-referenced, mounted on the fuel rail.
Throttle Body: Single-bore, cable-operated.
Intake Manifold: aluminum, two-stage variable intake manifold. Butterfly
valves inside the manifold open at higher RPM (approx. 4,500 rpm) to
switch from longer, torque-optimized runners to shorter, power-optimized
runners. Air Flow Meter: Uses a vane-type Air Flow Meter (AFM) or a
hot-wire Mass Air Flow (MAF) sensor depending on market.
Type: Full-pressure, force-fed wet-sump system.
Oil Pump: Trochoid-type (internal gear), driven by the crankshaft.
Oil Filter: Standard spin-on canister type, mounted centrally at the
front of the engine.
Oil Cooler: Optional or standard on some applications (e.g., SVX).
Typically an oil-to-coolant heat exchanger. Oil Capacity (including
filter): 5.8 liters (6.1 US quarts / 5.1 Imperial quarts).
Recommended Oil Grade: API SG/SH or later. Viscosity: SAE 10W-30 or
10W-40, high-quality mineral or semi-synthetic. Operating Oil Pressure:
At operating temperature: 294-490 kPa (3.0-5.0 kgf/cm2 / 43-71 psi) at
2,000 rpm. Idle pressure above 98 kPa (1.0 kgf/cm2 / 14 psi).
Type: Pressurized, forced circulation system. Features a dual-core
radiator to manage the thermal load of the six-cylinder engine. Water
Pump: Centrifugal, driven by the timing belt.
Thermostat: Wax pellet type. Opening temperature is 76°C (169°F) or 82°C
(180°F).
Radiator Pressure Cap: 108-137 kPa (1.1-1.4 kgf/cm2 / 16-20 psi).
Coolant Capacity (engine + radiator, approx.): 9.5 liters (10.0 US
quarts / 8.4 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 with a single
coil, rotor, and spark plug wires. The distributor is driven from the
left intake camshaft.
Spark Plugs: Standard nickel or platinum. Gap: 0.7-0.8 mm (0.028-0.031
in).
Emission Controls: Includes Exhaust Gas Recirculation (EGR), Positive
Crankcase Ventilation (PCV), and a three-way catalytic converter. US
models have OBD-I diagnostics.
Accessory Drive: Single serpentine belt driving the alternator, power
steering pump, and air conditioning compressor.
Length (from front of pulley to rear of block): 750 mm (29.5 inches).
Width (over cylinder heads): 1,000 mm (39.4 inches).
Height (from bottom of sump to top of intake manifold): 600 mm (23.6
inches).
Dry Weight (engine only, complete): 190-200 kg (419-441 lbs).
Engine Oil and Filter Change Interval: Every 7,500-10,000 km
(4,700-6,200 miles) or 6-12 months. Spark Plugs and Wires: Replace spark
plugs every 40,000-50,000 km (25,000-31,000 miles). Inspect and replace
ignition wires as needed. Timing Belt and Components: Replace timing
belt, hydraulic tensioner, and all idler pulleys every 100,000 km
(62,000 miles) or 5-7 years. This is a complex, expensive, but vital
service.
Valve Clearance Adjustment: Check and adjust (via shim replacement)
every 100,000 km (62,000 miles). Labor-intensive due to camshaft
removal. Accessory Drive Belt: Inspect and adjust tension regularly.
Replace at signs of wear. 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 20,000-30,000 km (12,400-18,600 miles).
Distributor Cap and Rotor: Replace every 40,000-50,000 km as part of a
major tune-up.
Cylinder Head Bolts (M11): Multi-stage torque procedure. Step 1: Tighten
all bolts in sequence to 34 Nm (25 lb-ft). Step 2: Tighten all bolts in
sequence to 69 Nm (51 lb-ft). Follow the specific sequence for each head
meticulously from center outwards.
Main Bearing Cap Bolts: 54-59 Nm (40-44 lb-ft).
Connecting Rod Cap Bolts: 45-50 Nm (33-37 lb-ft).
Flywheel to Crankshaft Bolts: 60-70 Nm (44-52 lb-ft) + 30-degree turn.
Crankshaft Pulley Bolt: 157-177 Nm (116-131 lb-ft).
Camshaft Sprocket Bolts: 78-88 Nm (58-65 lb-ft).
Spark Plugs: 18-22 Nm (13-16 lb-ft).
Oil Pan Bolts: 8-12 Nm (6-9 lb-ft).
Valve 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).
Timing Belt Tensioner Bolt: 39-49 Nm (29-36 lb-ft).
The Subaru EG33 engine was used in a very limited number of models,
cementing its exclusive status: Subaru SVX (1991-1996): The primary and
most famous application. Powering the Alcyone SVX sports coupe in all
markets (sold as the SVX in the US, Alcyone SVX in Japan, and Subaru SVX
elsewhere). This was its sole passenger car application. Subaru Sambar
EV (1996-1999): In a highly unusual application, the EG33 was used as a
range-extender generator in the electric version of the Sambar kei
truck/van. It did not drive the wheels but ran at a constant speed to
charge the batteries.
Experimental/Concept Vehicles: The engine has been used in various
Subaru concepts and has a strong following in the aviation and homebuilt
aircraft community (as a lightweight, smooth, powerful aircraft engine
conversion). The EG33 was never used in the Legacy, Outback, or
Forester. Its complexity, cost, and width made it unsuitable for mass
application in Subaru's mainstream lineup. It remains a legendary,
smooth, and sought-after engine by enthusiasts, representing Subaru's
ambitious foray into the grand touring sports coupe segment.
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