Subaru EZ30R Specifications
| Engine Model: Subaru EZ30R |
| Engine Type: 4-cycle 6-cylinder DOHC 24-valve liquid-cooled gasoline |
| Total Displacement: 183 cu.in (2.99 L) |
| Rated Engine Power: 245-250 Hp (183-186 kW) at 6600 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Subaru EZ30R, designated as the Phase II evolution
of the EZ30 family, is a 3.0-liter, naturally aspirated, horizontally opposed
six-cylinder engine introduced in 2003. Serving as Subaru’s premier powerplant
for the Legacy 3.0R, Outback 3.0R, and the B9 Tribeca, the EZ30R represented a
significant engineering advancement over its predecessor.
The defining characteristic of the "R" variant is the incorporation of Subaru’s
Active Valve Control System (AVCS) for variable intake cam timing and the
i-Active Valve Lift System (AVLS) for variable valve lift on the intake side, a
combination that allowed the engine to deliver a refined idle characteristic
alongside a high specific output. Constructed entirely from aluminum alloy with
dual overhead camshafts (DOHC) per cylinder bank and a maintenance-free timing
chain, the EZ30R produces 245 to 250 horsepower, positioning it competitively
against European luxury sport sedans.
The engine features a triple-port exhaust design per cylinder head, a
variable-length intake manifold, and an advanced engine management system
capable of coordinating the variable valve mechanisms. While renowned for its
smooth power delivery, distinctive flat-six exhaust note, and robust
construction, the EZ30R demands meticulous maintenance, particularly regarding
its cooling system and internal oil gallery seals.
The EZ30R is a longitudinally mounted, horizontally opposed six-cylinder engine
utilizing a wet-sump lubrication system. Its flat configuration inherently
balances primary and secondary forces without balance shafts, providing
exceptional smoothness. The engine management system coordinates AVCS on the
intake camshafts and AVLS on the intake valves, allowing for optimized
volumetric efficiency across the operating range. All variants employ sequential
multi-point fuel injection.
Engine Type: Horizontally opposed (Boxer) 6-cylinder, water-cooled petrol.
Displacement: 2,999 cc / 183.0 cu.in.
Bore: 89.2 mm / 3.51 in.
Stroke: 80.0 mm / 3.15 in.
Compression Ratio: 10.7:1.
Valvetrain: DOHC, 24 valves. AVCS on intake camshafts; AVLS on intake valves.
Fuel System: Multi-Point Fuel Injection (MPFI), sequential.
Firing Order: 1-6-3-2-5-4.
Maximum Power: 245-250 hp / 183-186 kW at 6,600 rpm.
Maximum Torque: 219 lb-ft / 297 Nm at 4,200 rpm.
Engine Oil Capacity (with filter): 5.5 L / 5.8 US qt.
Oil Grade: 5W-30 fully synthetic, API SL or higher.
Coolant Capacity: 6.5 L / 6.9 US qt.
The cylinder block is constructed from aluminum alloy
using a semi-closed deck design, a configuration that balances structural
rigidity with enhanced coolant flow around the cylinder bores. The aluminum
construction reduces overall engine weight, a critical consideration for the
engine’s placement ahead of the front axle in Subaru’s longitudinal layout. The
cylinder bores are cast with a high-silicon aluminum material utilizing a
plateau-honed finish, eliminating the need for separate cast-iron liners.
Within the block, a forged steel crankshaft with eight counterweights is
supported by seven main bearings, providing exceptional rigidity for the
six-cylinder configuration. The crankshaft incorporates a larger main journal
diameter than the earlier EZ30D to accommodate the increased power output.
Connecting rods are forged powder metal with a fracture-split design. The
pistons are aluminum alloy castings featuring a low-friction skirt coating and
reinforced ring lands to withstand the higher cylinder pressures of the 10.7:1
compression ratio. The oil pump is a gear-type unit mounted within the front
timing cover and driven directly by the crankshaft.
Each cylinder bank has its own aluminum alloy cylinder
head casting incorporating dual overhead camshafts. The EZ30R’s valvetrain
distinguishes itself through two advanced systems. AVCS (Active Valve Control
System) provides continuously variable intake camshaft timing across a range of
approximately 35 degrees of crank angle, optimizing volumetric efficiency across
the rev range.
AVLS (i-Active Valve Lift System) provides two distinct lift profiles on the
intake valves: a low-lift profile for improved low-end torque and fuel
efficiency, and a high-lift profile that engages above 3,500 rpm to increase
airflow and power output. The valvetrain utilizes roller rocker arms with
integrated hydraulic lash adjusters that automatically maintain zero valve
clearance. The exhaust system is a triple-port design per cylinder head, with
each cylinder exhausting through its own dedicated port rather than a merged
configuration, improving exhaust pulse isolation and scavenging efficiency.
Valve Configuration: DOHC per bank, 24 valves total
Intake Valve Diameter: 34.0 mm / 1.34 in
Exhaust Valve Diameter: 29.5 mm / 1.16 in
AVCS Range: 35 degrees of intake camshaft advance
AVLS Engagement: High-lift profile engages at 3,500-4,000 rpm, dependent on
throttle position and engine load. Camshaft Drive: Single-row timing chain with
hydraulic tensioner; chain is maintenance-free for the engine’s service life.
The EZ30R employs a sequential multi-point fuel
injection system. Fuel is delivered by an electric in-tank pump operating at a
regulated pressure of 3.5 bar / 50 psi to dual fuel rails mounted on the intake
manifold. The intake manifold is a two-piece composite plastic construction with
a variable induction system (VIS) featuring a resonance chamber and intake
runner length control.
A set of valves within the intake manifold switches between long runners for
low-end torque and short runners for high-end power. The fuel injectors are
high-impedance, 12-hole type, positioned to spray fuel directly onto the backs
of the intake valves. The system utilizes a returnless fuel delivery
configuration where the pressure regulator is integrated into the fuel pump
assembly.
Lubrication is provided by a high-volume gear-type oil
pump located within the front timing cover and driven directly by the
crankshaft. The lubrication system incorporates a water-to-oil cooler integrated
into the oil filter housing, using engine coolant to stabilize oil temperature
under sustained high-load operation.
The circuit supplies pressurized oil to the crankshaft main bearings, connecting
rod bearings, camshaft journals, AVCS actuators, AVLS mechanisms, hydraulic lash
adjusters, and the timing chain tensioner. Internal oil passages within the
cylinder block include gallery O-rings that seal the interface between the block
and the timing cover.
These O-rings are subject to hardening over
time, and their degradation can lead to oil pressure loss. The oil pan
is a cast aluminum unit with internal baffling to maintain oil pickup
under high lateral acceleration.
The cooling system is a forced circulation, pressurized
design engineered to manage the elevated thermal output of the 250 hp
six-cylinder engine. A belt-driven water pump with a cast impeller circulates
coolant through the aluminum cylinder block and cylinder heads. The water jacket
design was revised from the earlier EZ30D to provide improved cooling around the
cylinder bores and in the area between the cylinders.
The system utilizes a high-capacity cross-flow aluminum radiator with plastic
end tanks and an electric cooling fan controlled by the engine control unit. A
wax-type thermostat, rated at 82°C / 180°F, regulates coolant flow. The cooling
system has a relatively small coolant capacity relative to the engine’s
displacement and power output, making the system sensitive to coolant loss. A
separate coolant circuit supplies the oil cooler and the heater core.
Ignition System: The ignition system is a
distributorless, coil-on-plug design with individual ignition coils mounted
directly over each spark plug. The engine control unit manages ignition timing
based on inputs from the crankshaft position sensor, camshaft position sensors,
knock sensors, and air-fuel ratio feedback.
Intake System: The intake system incorporates a large-volume air cleaner housing
with a paper element and a mass air flow (MAF) sensor. The variable induction
system (VIS) within the intake manifold switches runner lengths at predetermined
engine speeds to optimize torque characteristics. A resonance chamber integrated
into the intake tract reduces induction noise while improving volumetric
efficiency.
Timing System: The camshafts are driven by a single-row roller chain with a
hydraulic tensioner. The timing chain system is designed for the life of the
engine and does not have a scheduled replacement interval. The water pump is
mounted externally and driven by the accessory belt, not by the timing chain, a
departure from earlier Subaru engine designs.
AVCS System: The Active Valve Control System uses oil pressure to actuate a
vane-type phaser on the intake camshaft sprocket. The engine control unit
modulates oil flow through a solenoid valve to advance or retard cam timing
based on engine speed, load, and temperature.
AVLS System: The i-Active Valve Lift System uses oil pressure to engage locking
pins on the intake rocker arms. At low engine speeds, the rocker arms operate on
a low-lift cam lobe. When engaged, the rocker arms lock together and follow a
high-lift cam lobe, increasing valve lift and duration.
Emissions Control: The engine employs a three-way catalytic converter with
closed-loop lambda feedback. Dual heated oxygen sensors upstream of the catalyst
provide air-fuel ratio data for each cylinder bank. Secondary oxygen sensors
downstream monitor catalyst performance. Positive Crankcase Ventilation (PCV)
and Evaporative Emission Control (EVAP) systems are incorporated.
Overall Length: 30.7 in / 780 mm
Overall Width: 31.5 in / 800 mm
Overall Height: 26.8 in / 680 mm
Engine Weight (dry, without ancillaries): 330 lb / 150 kg
Engine Weight (fully dressed with intake, exhaust, and alternator): 396 lb / 180
kg
Engine Oil and Filter: Replace every 3,750-7,500 miles
/ 6,000-12,000 km or 6-12 months, using 5W-30 fully synthetic oil meeting ILSAC
GF-4 or higher specifications. Timing Chain: No specified replacement interval.
Inspect for noise or slack if engine exhibits rattling on startup. Timing chain
tensioner and guides are serviceable if wear is detected. Spark Plugs:
Replacement interval is 60,000 miles / 100,000 km. Use NGK ILFR6B or equivalent
iridium spark plugs.
Coolant: Replace at 60,000 miles / 100,000 km or 5 years. Use phosphate-free,
silicate-free ethylene glycol coolant formulated for aluminum engines. Drive
Belt (Accessory Serpentine): Inspect at each oil change; replace every 60,000
miles / 100,000 km or if cracking, glazing, or fraying is evident. Tensioner and
idler pulley bearings are common wear items and should be inspected
concurrently. Air Cleaner Element: Replace every 15,000-30,000 miles /
24,000-48,000 km depending on operating conditions.
Fuel Filter: Replacement interval is 30,000-60,000 miles / 48,000-100,000 km;
the filter is integrated into the fuel pump assembly on most applications,
requiring pump removal for service. Valve Clearance: Not required due to
hydraulic lash adjusters; no adjustment interval specified. Oil Gallery O-Rings:
No specified replacement interval. Degraded O-rings may cause low oil pressure,
indicated by AVCS malfunction codes or timing chain rattle on startup.
Replacement requires removal of the timing cover and is considered an
extended-service overhaul procedure.
Cylinder Head Bolts (M10 x 1.25), Step 1: 22 lb-ft / 30
Nm.
Cylinder Head Bolts (M10 x 1.25), Step 2: 58 lb-ft / 80 Nm.
Crankshaft Pulley Bolt: 177 lb-ft / 240 Nm.
Camshaft Sprocket Bolts: 74 lb-ft / 100 Nm.
AVCS Phaser Mounting Bolts: 74 lb-ft / 100 Nm.
Connecting Rod Bearing Cap Bolts (M8 x 1.0): 14 lb-ft / 20 Nm.
Main Bearing Cap Bolts (M12 x 1.25), Step 1: 25 lb-ft / 35 Nm.
Main Bearing Cap Bolts (M12 x 1.25), Step 2: 58 lb-ft / 80 Nm.
Cylinder Head Cover Bolts (M6 x 1.0): 7-9 lb-ft / 10-12 Nm.
Intake Manifold Bolts: 14-18 lb-ft / 20-25 Nm.
Exhaust Manifold Nuts: 22-26 lb-ft / 30-35 Nm.
Spark Plugs: 18 lb-ft / 25 Nm.
Oil Filter (Spin-on): 18 lb-ft / 25 Nm.
Oil Pan Bolts (M6 x 1.0): 5-7 lb-ft / 7-10 Nm.
Timing Chain Tensioner Bolts: 18 lb-ft / 25 Nm.
Timing Cover Bolts (M6 x 1.0): 9 lb-ft / 12 Nm.
Water Pump Bolts (M6 x 1.0): 7-9 lb-ft / 10-12 Nm.
Flywheel / Drive Plate Bolts: 58 lb-ft / 80 Nm.
The EZ30R engine served as the flagship powerplant for
Subaru’s premium 3.0R trim levels across multiple model lines from 2003 through
2009.
Subaru Legacy 3.0R (BL / BP): 2003-2009 (sedan and wagon body styles).
Subaru Outback 3.0R (BP): 2004-2009 (wagon body style, featuring revised
suspension tuning for increased ground clearance).
Subaru Tribeca (B9 / WX): 2006-2007 (initial model years; replaced by the
3.6-liter EZ36 for the 2008 model year).
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