Subaru EJ20X Specifications
| Engine Model: Subaru EJ20X |
| Engine Type: 4-cycle 4-cylinder DOHC 16-valve turbocharged liquid-cooled gasoline |
| Total Displacement: 121.7 cu.in (1.99 L) |
| Rated Engine Power: 256-276 Hp (191-206 kW) at 6500 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
____________________________________________________________________________________
The Subaru EJ20X is a 2.0-liter turbocharged
horizontally opposed Boxer engine introduced in 2003 as the flagship powertrain
for the fourth-generation Legacy (BL/BP) in the Japanese Domestic Market (JDM).
Designed specifically for pairing with automatic transmissions, the EJ20X
represented the culmination of Subaru’s turbocharged engine development for the
Legacy platform, delivering a broad torque curve and refined power delivery
through advanced valvetrain and turbocharging technologies. Its sister engine,
the EJ20Y, was calibrated for manual transmission applications.
The EJ20X’s architecture centers on the traditional Subaru Boxer configuration:
a flat-four layout with a 180-degree cylinder bank angle that lowers the center
of gravity and reduces engine length for longitudinal mounting. The engine
incorporates Dual Active Valve Control System (AVCS) on both intake and exhaust
camshafts, a significant advancement over earlier EJ-series engines that offered
AVCS on the intake side only. This dual system enabled precise valve timing
control across the engine speed range, contributing to a torque plateau that
peaked at 343 Nm from 2,400 rpm.
The induction system utilized a twin-scroll turbocharger - initially the
titanium-wheeled VF38, later replaced by VF44 and VF45 units - which minimized
turbocharger lag and provided responsive power delivery. The EJ20X employed an
open-deck cylinder block design, prioritizing cooling efficiency for sustained
high-performance operation. Its high compression ratio of 9.5:1, elevated for a
turbocharged engine, delivered responsive off-boost throttle response but
demanded high-quality fuel and precise engine management to prevent detonation.
Engine Type: Horizontally opposed (Boxer) 4-cylinder, 4-cycle, turbocharged.
Displacement: 1,994 cc (121.7 cu.in).
Bore: 92.0 mm (3.62 in).
Stroke: 75.0 mm (2.95 in).
Compression Ratio: 9.5:1.
Firing Order: 1-3-2-4.
Maximum Power: 191-206 kW (256-276 hp) @ 6,000-6,500 rpm.
Maximum Torque: 343 Nm (253 lb-ft) @ 2,400 rpm.
Redline: 7,000 rpm with fuel cutoff at 7,200-7,500 rpm depending on ECU
calibration.
Valvetrain Configuration: Dual Overhead Camshaft (DOHC) per cylinder bank,
operating 16 valves (4 valves per cylinder). Dual Active Valve Control System
(AVCS) on intake and exhaust camshafts. Camshafts are driven by a rubber timing
belt.
The cylinder block is manufactured from cast aluminum
alloy using high-pressure die-casting techniques, consistent with the Subaru
Boxer engine tradition. The block incorporates the open-deck design, where the
cylinder bores are supported only at the upper and lower extremes with no
structural reinforcement between the bores at the deck surface. This design
prioritizes cooling efficiency - coolant flows freely around the upper cylinder
regions - over ultimate cylinder rigidity, making the EJ20X well-suited for its
intended power output range but less suitable for extreme high-boost
modifications exceeding 300-350 kW (400-470 hp).
The cylinder bores are cast-in-place iron liners, centrifugally cast and
machined to final specification. Bore diameter measures 92.0 mm (3.62 in) with a
piston stroke of 75.0 mm (2.95 in), yielding a total displacement of 1,994 cc
(121.7 cu.in). This over-square bore-to-stroke ratio (1.227) favors high-rpm
power production and reduces mean piston speed, contributing to the engine’s
elevated redline capability. The block incorporates the characteristic
180-degree horizontal cylinder orientation, with the crankshaft positioned
centrally between the two banks.
The crankshaft is forged from chromium-molybdenum steel with induction-hardened
journal surfaces. Five main bearings support the crankshaft, with main bearing
journal diameter measuring 58.0 mm (2.28 in). Thrust washers positioned at the
center main bearing control axial crankshaft play. Connecting rods are forged
from high-carbon steel with an I-beam cross-section, featuring a fracture-split
big end design introduced in later production.
Pistons are cast aluminum with a low-expansion
silicon alloy, featuring two compression rings and one oil control ring.
The piston crown incorporates a shallow combustion bowl designed to
accommodate the 9.5:1 compression ratio while providing adequate valve
clearance for the dual AVCS valvetrain.
Oil squirters (piston cooling jets) are integrated into the cylinder
block, directing a stream of pressurized oil to the underside of each
piston crown to manage thermal loads during sustained high-output
operation.
Two cylinder heads are utilized, one for each cylinder
bank, manufactured from aluminum alloy. The cross-flow design separates intake
and exhaust passages to opposite sides of each head, with the intake ports
positioned on the upper inner surfaces of the engine and the exhaust ports on
the outer sides. The combustion chambers are of the pent-roof configuration with
four valves per cylinder.
Each cylinder head contains 16 valves: eight intake valves and eight exhaust
valves across both banks. Intake valve diameter measures 32.5 mm (1.28 in),
while exhaust valve diameter measures 28.5 mm (1.12 in). Valve stem diameter is
5.5 mm (0.22 in) for both intake and exhaust. The exhaust valves are
sodium-filled to enhance heat transfer from the valve head to the valve guide, a
necessity given the elevated exhaust gas temperatures generated by the
twin-scroll turbocharger.
The Dual Active Valve Control System (AVCS) is the defining feature of the EJ20X
valvetrain. Hydraulic camshaft phasers are mounted on the front of both intake
and exhaust camshafts on each cylinder bank, providing continuously variable
valve timing across a range of 50 degrees crankshaft angle on the intake side
and 40 degrees on the exhaust side. The system is actuated by oil control valves
(OCVs) commanded by the engine control unit, with position feedback provided by
camshaft angle sensors. This dual AVCS enables precise control of valve overlap
across the operating range, optimizing volumetric efficiency, reducing
emissions, and contributing to the engine’s broad torque curve.
The camshafts are driven by a rubber timing belt with a trapezoidal tooth
profile. The belt routes from the crankshaft sprocket to the right bank exhaust
camshaft sprocket, then to the left bank exhaust camshaft sprocket, and finally
to the tensioner and idler pulleys. Separate secondary belt segments connect the
exhaust camshaft sprocket to the intake camshaft sprocket on each bank. An
automatic spring-loaded tensioner maintains correct belt tension. The timing
belt service interval is 100,000 km (62,000 mi) or 5 years.
Valve clearance is maintained via bucket tappets with shim adjustment.
Inspection interval is 100,000 km (62,000 mi). Intake valve clearance
specification is 0.20-0.25 mm (0.008-0.010 in) cold; exhaust valve clearance is
0.20-0.25 mm (0.008-0.010 in) cold.
The EJ20X employs a multi-point electronic fuel
injection system operating in sequential mode. Fuel delivery is managed by the
engine control unit based on inputs from the mass airflow sensor, crankshaft
position sensor, camshaft position sensors, engine coolant temperature sensor,
intake air temperature sensor, throttle position sensor, and front and rear
oxygen sensors.
Fuel injectors are top-feed, solenoid-actuated units with high flow capacity to
accommodate the engine’s power output. Injector flow rate is approximately 550
cc/min (52 lb/hr) at the standard 3.0 bar (44 psi) fuel pressure. The fuel rail
is manufactured from stainless steel and mounted to the intake manifold on each
cylinder bank, delivering fuel to all four injectors. System fuel pressure is
regulated by a returnless system with the pressure regulator integrated into the
fuel tank module.
The intake manifold is constructed from aluminum alloy with dual plenums and
runners tuned for the twin-scroll turbocharger configuration. The throttle body
is an electronically controlled unit (drive-by-wire) with a bore diameter of 65
mm (2.56 in). A boost pressure sensor and intake air temperature sensor are
integrated into the manifold.
The lubrication system utilizes a forced-feed,
full-flow design with a trochoid-type oil pump mounted to the front of the
crankshaft. The pump is driven directly by the crankshaft nose, providing oil
flow proportional to engine speed. A pressure relief valve integrated into the
pump maintains system pressure within design parameters.
Total oil capacity including filter is 4.8-5.0 liters (5.1-5.3 qt). Recommended
oil viscosity is 5W-30 or 5W-40, with API classification SM or SN for synthetic
formulations. Oil pressure specifications require a minimum of 1.0 bar (15 psi)
at warm idle and 4.0-5.0 bar (58-73 psi) at 3,000 rpm.
The oil filter is a spin-on, full-flow type mounted to the cylinder block. A
liquid-to-oil plate-type oil cooler is integrated into the lubrication system,
mounted between the oil filter and the cylinder block, utilizing engine coolant
to stabilize oil temperature. The oil pan is stamped steel with internal
baffling to maintain oil pickup under high lateral acceleration.
The cooling system is pressurized and utilizes a
centrifugal water pump driven by the accessory drive belt. The pump features a
cast aluminum housing and a composite impeller. Coolant circulation is
controlled by a wax-pellet thermostat located in the coolant outlet housing.
Thermostat opening temperature is 82-86 °C (180-187 °F), with full valve lift
achieved at 95 °C (203 °F). The system incorporates a bypass circuit that allows
coolant circulation within the engine during warm-up.
Total coolant capacity ranges from 7.5-8.5 liters (7.9-9.0 qt), inclusive of the
engine block, radiator, heater core, oil cooler circuit, and turbocharger
cooling circuit. The radiator is a high-efficiency cross-flow aluminum core with
plastic end tanks. Cooling fan configuration consists of dual electric fans
controlled by the engine control unit. System pressure is controlled by a
radiator cap rated at 1.1 bar (16 psi).
Aspiration System: The EJ20X is equipped with a
twin-scroll turbocharger. Early production (2003-2006) utilized the Mitsubishi
VF38, featuring a titanium-aluminide turbine wheel for reduced inertia and
improved transient response. Later variants received the VF44 and VF45
turbochargers, which employed conventional nickel-alloy turbine wheels with
revised compressor and turbine housing geometries. The twin-scroll turbine
housing separates exhaust pulses from cylinders 1 and 2 from those of cylinders
3 and 4, maintaining exhaust energy separation to the turbine wheel and
minimizing turbocharger lag. An air-to-air intercooler is mounted in the
front-end cooling package (front-mount intercooler) on Legacy GT applications,
reducing intake air temperature under sustained boost conditions. Maximum boost
pressure ranges from 0.8-1.0 bar (12-15 psi) depending on engine speed and
calibration.
Exhaust System: The exhaust manifold is constructed from equal-length stainless
steel tubing (equal-length header), a configuration that optimizes exhaust pulse
timing for the twin-scroll turbocharger. This design eliminates the uneven
exhaust pulse spacing that produces the traditional “Subaru rumble”
characteristic of unequal-length header designs, resulting in a smoother, more
refined exhaust note. The system incorporates a three-way catalytic converter
with closed-loop oxygen sensor feedback. Two wideband oxygen sensors are
utilized: one pre-catalyst and one post-catalyst.
Engine Management: The Ecu.integrates control of fuel injection, ignition
timing, boost pressure via a solenoid-controlled wastegate actuator, dual AVCS
camshaft phasing, idle speed control, and cooling fan operation. The system
utilizes a 32-bit processor and incorporates a mass airflow sensor for direct
air mass measurement. Ignition system utilizes direct-acting ignition coils
mounted over each spark plug (coil-on-plug). Spark plug type is iridium-tipped
with a gap of 0.6-0.7 mm (0.024-0.028 in). Spark plug replacement interval is
60,000 km (37,000 mi).
Timing System: The timing belt incorporates an automatic tensioner with a
hydraulic damper and a spring-loaded idler pulley. Timing marks are cast into
the timing belt covers and sprockets for synchronization verification.
Crankcase Ventilation: A closed-loop PCV system routes blow-by gases from the
cylinder block and valve covers through an oil separator, returning condensed
oil to the sump while directing vapor to the intake system upstream of the
turbocharger compressor inlet.
Overall Length: 590 mm (23.2 in) measured from
accessory drive pulley face to transmission mounting flange.
Overall Width: 860 mm (33.9 in) inclusive of the cylinder heads and intake
manifold assembly.
Overall Height: 570 mm (22.4 in) from oil pan bottom surface to valve cover top
surface.
Dry Weight: 150-160 kg (331-353 lb) depending on turbocharger configuration and
accessory equipment.
Valve Clearance (cold): Intake: 0.20-0.25 mm
(0.008-0.010 in). Exhaust: 0.20-0.25 mm (0.008-0.010 in). Inspection interval:
100,000 km (62,000 mi). Adjustment performed via replacement of bucket tappet
shims. Timing Belt Replacement Interval: 100,000 km (62,000 mi) or 5 years.
Replacement includes belt, tensioner, idler pulleys, and water pump. Spark Plug
Replacement Interval: 60,000 km (37,000 mi) for iridium-tipped plugs. Spark plug
torque: 22-25 Nm (16-18 lb-ft).
Engine Oil Change Interval: 8,000 km (5,000 mi) for standard driving conditions;
5,000 km (3,100 mi) for severe service including sustained high-rpm operation,
track use, or dusty environments. Full synthetic oil required. Oil Filter
Replacement Interval: Replace with every oil change. Fuel Filter Replacement
Interval: 60,000 km (37,000 mi) for in-line filter mounted in the engine bay.
Air Filter Element Replacement Interval: 30,000 km (18,600 mi) or as indicated
by inspection.
Coolant Change Interval: 60,000 km (37,000 mi) or 3 years. Drive Belt
(accessory) Replacement Interval: 60,000 km (37,000 mi) or when cracking,
glazing, or wear is observed. Idle Speed (warm, neutral): 700-800 rpm,
controlled by ECU. Ignition Timing: Electronically controlled. No manual
adjustment possible. Fuel Pressure: 3.0-3.5 bar (44-51 psi) measured at fuel
rail with engine running. Compression Pressure: Minimum 12.0 bar (174 psi) with
no cylinder varying more than 1.5 bar (22 psi) from others. Measured with engine
warm, throttle fully open. Boost Pressure (maximum): 0.8-1.0 bar (12-15 psi)
depending on calibration.
Cylinder Head Bolts (cold), Step 1: 30 Nm (22 lb-ft).
Cylinder Head Bolts (cold), Step 2: 60 Nm (44 lb-ft).
Crankshaft Damper Pulley Bolt: 170-180 Nm (125-133 lb-ft).
Connecting Rod Cap Bolts: 45-50 Nm (33-37 lb-ft).
Main Bearing Cap Bolts: 65-70 Nm (48-52 lb-ft).
Flywheel / Drive Plate Bolts: 70-80 Nm (52-59 lb-ft).
Camshaft Sprocket Bolts: 50-60 Nm (37-44 lb-ft).
Camshaft Phaser Mounting Bolts: 50-60 Nm (37-44 lb-ft).
Camshaft Bearing Cap Bolts: 15-20 Nm (11-15 lb-ft).
Valve Cover Bolts: 8-10 Nm (6-7 lb-ft).
Intake Manifold Bolts: 18-22 Nm (13-16 lb-ft).
Exhaust Manifold Nuts: 25-30 Nm (18-22 lb-ft).
Turbocharger Mounting Nuts: 35-40 Nm (26-30 lb-ft).
Turbocharger Oil Feed Line: 20-25 Nm (15-18 lb-ft).
Turbocharger Coolant Lines: 25-30 Nm (18-22 lb-ft).
Oil Pan Bolts: 8-12 Nm (6-9 lb-ft).
Timing Belt Tensioner Bolt: 20-25 Nm (15-18 lb-ft).
Idler Pulley Bolts: 35-40 Nm (26-30 lb-ft).
Water Pump Mounting Bolts: 15-20 Nm (11-15 lb-ft).
Thermostat Housing Bolts: 8-12 Nm (6-9 lb-ft).
Fuel Rail Mounting Bolts: 18-22 Nm (13-16 lb-ft).
Spark Plugs: 22-25 Nm (16-18 lb-ft).
Crankshaft Position Sensor Mounting Bolt: 8-10 Nm (6-7 lb-ft).
Camshaft Position Sensor Mounting Bolts: 8-10 Nm (6-7 lb-ft).
Oxygen Sensors: 40-45 Nm (30-33 lb-ft).
Subaru Legacy GT (BL5 / BP5): 2003-2009 model years.
The EJ20X served as the high-performance powertrain for the fourth-generation
Legacy GT sedan (BL5) and wagon (BP5) equipped with automatic transmissions. The
engine was paired exclusively with the five-speed electronically controlled
automatic transmission (5EAT), which featured manual shift mode and adaptive
shift logic calibrated to the engine’s torque characteristics. Power output
varied by year: early models (2003-2006) produced 260 PS; later models
(2006-2009) produced 280 PS.
Subaru Legacy 2.0GT Spec B (BL5 / BP5): 2003-2009 model years. The Spec B
variant, featuring Bilstein suspension and additional chassis reinforcements,
received the EJ20X when equipped with automatic transmission. This combination
provided the enhanced handling characteristics of the Spec B chassis with the
refined power delivery of the EJ20X and 5EAT pairing.
Subaru Exiga GT (YA5): 2008-2012 model years. The EJ20X was installed in the
Exiga GT, a three-row crossover wagon produced for the JDM market. This
application utilized the engine’s broad torque curve to provide adequate
performance for the heavier Exiga platform, paired with the five-speed automatic
transmission in a transverse-mounted configuration adapted from the Legacy
platform.
Aftermarket and Import Applications: The EJ20X has gained popularity as a
replacement engine for non-JDM Subaru vehicles, including USDM Subaru Impreza
WRX, Forester XT, and Legacy GT models. Importers supply the EJ20X as a
lower-cost alternative to the EJ207. Installation requires wiring modifications
to accommodate the dual AVCS system, or deletion of exhaust AVCS functionality,
and may require repinning of the engine harness to match the donor vehicle’s ECU
configuration. The twin-scroll turbocharger and equal-length exhaust manifold
require corresponding modifications to the vehicle’s exhaust system.
____________________________________________________________________________________
| Car Engines Technical Specifications |
| Small Engines Technical Specifications |
| Industrial Engines Technical Specifications |
| Outboard Engines Technical Specifications |
