Subaru EL15 Specifications
| Engine Model: Subaru EL15 |
| Engine Type: 4-cycle 4-cylinder DOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 91.4 cu.in (1.49 L) |
| Rated Engine Power: 110 Hp (81 kW) at 6400 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Subaru EL15 is a 1.5-liter naturally aspirated
flat-four engine introduced in 2005 as the entry-level powerplant for the
Impreza in Japan, Europe, and other international markets. Developed to replace
the older EJ15, the EL15 represented a modernization of Subaru’s
small-displacement engine strategy, incorporating a double overhead camshaft
(DOHC) valvetrain with four valves per cylinder and active valve control on the
intake side. The engine utilized an aluminum block with cast iron cylinder
liners and aluminum cylinder heads, continuing Subaru’s horizontally opposed
architecture that provided a low center of gravity.
The EL15 featured a compression ratio of 10.1:1, producing 110 hp and 144 Nm of
torque with a free-revving character to its 6,400 rpm power peak. The engine
introduced AVCS (Active Valve Control System) variable valve timing on the
intake camshafts, a feature absent from the earlier EJ15, contributing to
improved fuel efficiency and a broader torque curve. The EL15 powered the
base-model Impreza across two generations before being superseded by the
FB-series engines.
Engine Type: 4-stroke, horizontally opposed 4-cylinder (flat-four), gasoline
engine.
Displacement: 1,498 cc (1.5 L; 91.4 cu.in).
Bore: 77.7 mm (3.059 in).
Stroke: 79.0 mm (3.110 in).
Compression Ratio: 10.1:1.
Firing Order: 1-3-2-4.
Combustion Chamber: Pent-roof design with centrally located spark plugs.
Aspiration: Naturally aspirated.
Maximum Power: 81 kW (110 hp; 112 PS) at 6,400 rpm.
Maximum Torque: 144 Nm (106 lb-ft) at 3,200 rpm.
Maximum Engine Speed: 6,800 rpm (fuel cut).
Compression Pressure
Standard: 1.25-1.45 MPa (181-210 psi).
Minimum service limit: 1.05 MPa (152 psi).
Maximum permissible variation between cylinders: 0.10 MPa (15 psi).
Valvetrain: DOHC (double overhead camshaft per cylinder bank), 4 valves per
cylinder, 16 valves total, timing belt drive, AVCS (Active Valve Control System)
on intake camshafts.
The cylinder block is constructed from aluminum alloy
with cast-in iron cylinder liners, utilizing Subaru’s horizontally opposed
architecture where the two banks of cylinders face each other at 180 degrees.
The block is split along the crankshaft centerline, comprising an upper block
and a lower bedplate assembly that secures the crankshaft main bearings. This
bedplate design enhances structural rigidity and reduces vibration compared to
traditional main bearing cap configurations. Five main bearings support the
forged steel crankshaft.
The cylinder liners are machined to a plateau-honed finish after casting. The
block incorporates an integral oil gallery network and coolant passages
surrounding each cylinder for the full depth of the stroke. Lightweight cast
aluminum pistons with reduced mass compared to the EJ15 are fitted, connected to
the crankshaft through forged steel connecting rods. The engine mounts are
positioned on the sides of the block to accommodate the low-profile flat
configuration.
Each cylinder bank receives an aluminum alloy cylinder
head with pent-roof combustion chambers and a cross-flow design positioning
intake ports on the inner side of the Vee and exhaust ports on the outer side.
The dual overhead camshafts per cylinder bank are supported by five bearing
journals each. The intake camshaft on each bank incorporates an AVCS actuator
that allows continuously variable adjustment of intake valve timing up to 40
degrees of crankshaft rotation.
The camshafts are driven by a toothed timing belt from the crankshaft, with an
automatic tensioner maintaining belt tension. Valve actuation occurs through
bucket-type tappets with shim adjustment. The intake ports are designed with a
high-tumble geometry to promote charge motion and mixture preparation. The
equal-length exhaust manifold design produces a smoother exhaust note compared
to the unequal-length manifolds of many EJ-series engines.
Number of Valves: 16 total (4 per cylinder).
Intake Valve Diameter: 30.0 mm (1.181 in).
Exhaust Valve Diameter: 26.0 mm (1.024 in).
Valve Stem Diameter: 5.5 mm (0.217 in) for both intake and exhaust.
Valve Seat Inserts: Powder metal inserts for both intake and exhaust.
Valve Clearance: Shim adjustment under bucket; clearance measured with engine
cold.
Intake Valve Clearance (cold): 0.20-0.30 mm (0.008-0.012 in).
Exhaust Valve Clearance (cold): 0.25-0.35 mm (0.010-0.014 in).
Valve Timing (AVCS at maximum advance)
Intake Opens: 30° BTDC.
Intake Closes: 60° ABDC.
Exhaust Opens: 50° BBDC.
Exhaust Closes: 10° ATDC.
The fuel system employs a returnless electronic
multi-point fuel injection design with sequential injection timing. A single
in-tank electric fuel pump delivers fuel through a stainless steel fuel rail
mounted to the intake manifold. The system operates at a nominal pressure
regulated by a pressure regulator integrated with the fuel pump module. Each
cylinder is served by a side-feed injector positioned to direct fuel spray onto
the back of the intake valves.
The engine management system uses a mass airflow sensor and a heated oxygen
sensor upstream of the catalytic converter to maintain closed-loop fuel control
under most operating conditions. The intake manifold is a composite construction
designed for compact packaging within the engine bay.
Injectors: Side-feed, high-impedance; flow rate of 150-170 cc/min at 350 kPa.
Fuel Filtration: In-tank primary strainer and replaceable inline filter rated at
10 microns.
Fuel Pressure: 330-370 kPa (48-54 psi) at idle; maintained by returnless system.
Fuel Specification: Regular unleaded 91 RON minimum.
The lubrication system utilizes a gear-type oil pump
mounted to the front of the cylinder block and driven directly by the
crankshaft. The pump draws oil from a baffled steel sump through a strainer
screen and delivers it to a full-flow disposable cartridge oil filter mounted on
the side of the block.
The system incorporates a pressure relief valve calibrated to maintain stable
pressure across the operating range. Main galleries distribute oil to the
crankshaft main bearings, connecting rod bearings, camshaft bearings, and the
AVCS actuators. The AVCS system requires a dedicated oil control valve on each
cylinder head to regulate oil pressure to the camshaft actuators.
Oil Pump Type: Gear-type, crankshaft-driven.
Oil Pressure (hot, at 3,000 rpm): 300-400 kPa (44-58 psi).
Oil Pressure (hot, idle): 100 kPa (15 psi) minimum.
Oil Capacity (with filter): 4.0 L (4.2 US qt).
Oil Specification: API SM, SN, or higher; SAE 5W-30 for most climates; SAE
10W-30 for sustained high ambient temperatures above 30 °C (86 °F).
The cooling system employs a belt-driven centrifugal
water pump mounted to the front of the engine block. Coolant flows from the
radiator through the pump, then through the cylinder block water jacket, upward
into the cylinder heads, and returns to the radiator through a thermostat
housing located at the front of the intake manifold. A wax-pellet thermostat
with a bypass circuit maintains operating temperature stability.
The system incorporates a cross-flow aluminum radiator with a pressure-type
filler cap rated at 108-127 kPa (16-18 psi). A separate heater circuit draws
coolant from the cylinder heads through the heater core and returns to the water
pump inlet. The cooling system is designed to maintain consistent cylinder head
temperatures to support the AVCS system’s reliable operation.
Water Pump Type: Belt-driven centrifugal pump with cast aluminum housing and
stamped steel impeller. Coolant Capacity (engine and radiator): 6.0-7.0 L
(6.3-7.4 US qt) depending on heater core configuration. Thermostat Opening
Temperature: 82 °C (180 °F). Thermostat Fully Open Temperature: 95 °C (203 °F).
Coolant Specification: Ethylene-glycol based with aluminum-compatible corrosion
inhibitors; 50% concentration.
| Intake and Exhaust Systems |
Intake System: Air enters through a paper-element air
cleaner housing with an integrated mass airflow sensor, then passes through an
electronically controlled throttle body. The intake manifold is a composite
construction with integrated resonance chambers to reduce induction noise. The
manifold incorporates a variable-length runner system on certain applications,
with a control valve that alters effective runner length based on engine speed.
Exhaust System: Stainless steel exhaust manifold with equal-length runners for
each cylinder bank, merging into a single-pipe system leading to a catalytic
converter and underfloor muffler. The equal-length design eliminates the
characteristic Subaru rumble associated with unequal-length manifolds, producing
a smoother exhaust note. The system incorporates a heated oxygen sensor upstream
of the catalytic converter for closed-loop fuel control, with a downstream
sensor for catalyst efficiency monitoring.
| Ignition and Electrical System |
Ignition System: Direct ignition system with individual
coil-on-plug units mounted to each cylinder head, eliminating spark plug wires.
This system improves ignition reliability compared to the distributor or
pack-and-wire systems used on earlier EJ-series engines. The engine control unit
provides individual cylinder timing control with a knock sensor to maintain
optimal ignition advance across varying fuel qualities.
Electrical System: 12 V negative-ground electrical architecture. Starter motor
is a reduction-gear type mounted to the transmission bellhousing. Alternator
output is 90 A or 110 A depending on vehicle specification. Engine control unit
is a Hitachi or Denso unit with integrated knock control, sequential fuel
injection, AVCS management, and electronic throttle control.
AVCS System: The Active Valve Control System operates
on the intake camshafts only. Each intake camshaft is equipped with a vane-type
hydraulic actuator with a range of 40 degrees of crankshaft rotation. The engine
control unit determines optimal intake timing based on engine speed, load, and
coolant temperature, allowing variable overlap with the exhaust valves to
enhance low-end torque, fuel efficiency, and internal exhaust gas recirculation
for emissions reduction.
Length (front of accessory drive to rear of flywheel
housing): 670 mm (26.4 in).
Width (overall, across cylinder heads): 710 mm (28.0 in).
Height (from oil pan rail to top of intake manifold): 590 mm (23.2 in).
Dry Weight (complete engine with flywheel and manifolds): 125 kg (276 lb).
Dry Weight (complete engine with alternator, starter, and accessories): 138 kg
(304 lb).
Engine Oil: API SM, SN, or higher; SAE 5W-30 or SAE
10W-30.
Oil Change Interval: 7,500 km (4,700 mi) for severe service.
Oil Change Interval: 15,000 km (9,300 mi) for normal highway operation.
Oil Filter Replacement: Every oil change; use OEM or equivalent high-efficiency
filter.
Coolant Capacity: 6.0-7.0 L (6.3-7.4 US qt).
Coolant Change Interval: 60,000 km (37,000 mi) or 48 months.
Fuel Filter Replacement: 60,000 km (37,000 mi).
Air Filter Replacement: 30,000 km (18,600 mi).
Timing Belt Replacement: 100,000 km (62,000 mi) or 60 months.
Valve Clearance Inspection: 100,000 km (62,000 mi).
Spark Plugs: NGK ILFR6B or Denso VKH20 (iridium); gap: 1.0-1.1 mm (0.039-0.043
in).
Spark Plug Replacement Interval: 100,000 km (62,000 mi) for iridium type.
Idle Speed (closed throttle, transmission in neutral): 650-750 rpm.
Drive Belt Tension: Automatic tensioner; no manual adjustment required.
Cylinder Head Bolts (M11), Stage 1: 30 Nm (22 lb-ft).
Cylinder Head Bolts (M11), Stage 2: 60 Nm (44 lb-ft).
Main Bearing Cap Bolts (M10-bedplate to block), Stage 1: 20 Nm (15 lb-ft).
Main Bearing Cap Bolts (M10-bedplate to block), Stage 2: 45 Nm (33 lb-ft).
Connecting Rod Cap Bolts (M9): 20 Nm (15 lb-ft).
Flywheel / Flexplate Bolts (M12): 60 Nm (44 lb-ft).
Camshaft Bearing Caps (M8): 20-22 Nm (15-16 lb-ft).
Camshaft Sprocket Bolts (M10-AVCS actuators): 80-90 Nm (59-66 lb-ft).
Timing Belt Tensioner Bolt: 25-30 Nm (18-22 lb-ft).
Intake Manifold Bolts (M8): 20-22 Nm (15-16 lb-ft).
Exhaust Manifold Bolts (M10): 35-40 Nm (26-30 lb-ft).
Valve Cover Bolts (M6): 8-10 Nm (6-7 lb-ft).
Oil Pan Bolts (M6): 8-10 Nm (6-7 lb-ft).
Oil Pump Mounting Bolts (M8): 20-22 Nm (15-16 lb-ft).
Water Pump Bolts (M8): 20-22 Nm (15-16 lb-ft).
Thermostat Housing Bolts (M8): 20-22 Nm (15-16 lb-ft).
Spark Plugs: 25-30 Nm (18-22 lb-ft).
Engine Mount Bracket to Block (M10): 45-55 Nm (33-41 lb-ft).
Crankshaft Pulley Bolt (M16): 150-170 Nm (111-125 lb-ft).
Alternator Mounting Bolts (M10): 35-40 Nm (26-30 lb-ft).
Starter Motor Mounting Bolts (M10): 40-45 Nm (30-33 lb-ft).
Knock Sensor Bolt (M8): 20-22 Nm (15-16 lb-ft).
AVCS Oil Control Valve Bolts (M6): 8-10 Nm (6-7 lb-ft).
Subaru Impreza (GD4 / GG4): 2005-2007 model years; late
second-generation (Hawkeye) JDM and European market base models with EL15
engine; sedan and wagon body styles.
Subaru Impreza (GH2 / GH3): 2007-2011 model years; third-generation Impreza with
EL15 engine in base trim for Japan, Europe, Australia, and other international
markets; available with front-wheel drive and all-wheel drive configurations.
Subaru Impreza Anesis: Japanese Domestic Market variant of the GH2 with EL15
engine, emphasizing comfort and fuel efficiency.
Subaru Impreza XV: 2010-2011 crossover variant with EL15 engine in base trim for
selected markets.
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