Subaru EJ207 Specifications
| Engine Model: Subaru EJ207 |
| Engine Type: 4-cycle 4-cylinder SOHC 16-valve turbocharged liquid-cooled gasoline |
| Total Displacement: 121.7 cu.in (1.99 L) |
| Rated Engine Power: 276-315 Hp (206-235 kW) at 6400 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Subaru EJ207 is a 2.0-liter, turbocharged,
horizontally opposed four-cylinder gasoline engine produced from 1998 through
2021 as the pinnacle of the Subaru EJ20 series. Developed exclusively for the
Japanese domestic market (JDM) Impreza WRX STi, the EJ207 was engineered to
deliver high specific output with exceptional durability at elevated engine
speeds. Unlike the larger-displacement EJ257 used in North American market STi
models, the EJ207 retained the 2.0-liter displacement favored in Japan due to
taxation structures and motorsport regulations.
The EJ207 engine represents Subaru’s dedication to the high-performance
turbocharged boxer architecture that defined the Impreza WRX STi’s motorsport
heritage. The engine’s 1,994 cc displacement is achieved through a bore of 92.0
mm and a stroke of 75.0 mm, an oversquare configuration that favors high-rpm
power delivery - a characteristic essential for the engine’s 8,000-8,250 rpm
redline. The horizontally opposed (boxer) configuration provides a low center of
gravity and inherent balance, contributing to the vehicle’s handling dynamics.
The semi-closed deck cylinder block, featuring additional material around the
cylinder bores, provides superior resistance to bore distortion under high boost
pressures compared to the open-deck EJ205 used in standard WRX models. Versions
7 through 9 incorporated forged pistons and a cross-drilled, nitrided
crankshaft, components selected for their ability to withstand the thermal and
mechanical stresses of sustained high-rpm operation. The AVCS system, introduced
on the intake camshafts in Version 7 and expanded to dual AVCS (intake and
exhaust) in Version 10, optimized valve timing for improved low-end torque and
emissions.
The turbocharger configuration evolved from single-scroll units in early
versions to twin-scroll turbochargers with equal-length headers in later
versions, improving transient response and reducing exhaust gas temperatures.
The EJ207’s status within the Subaru community is defined by its ability to
reliably support power outputs exceeding 400 wheel horsepower with appropriate
engine management and fueling upgrades, a testament to the robustness of its
internal architecture.
Production Period: 1998 - 2021.
Engine Code: EJ207.
Configuration: Horizontally opposed four-cylinder (Boxer).
Displacement: 1,994 cc (121.7 cu.in).
Bore: 92.0 mm (3.62 in).
Stroke: 75.0 mm (2.95 in).
Firing Order: 1-3-2-4.
Compression Ratio: 8.0:1 (Versions 5-7).
Compression Ratio: 8.5:1 (Versions 8-9); 9.0:1.
Compression Ratio: 9.0:1 (Version 10 with twin-scroll).
Combustion System: Sequential multipoint fuel injection.
Aspiration: Single turbocharger with intercooler.
Valvetrain: DOHC, 16 valves (4 per cylinder), AVCS (variable valve timing).
Maximum Engine Speed: 8,000-8,250 rpm (redline, version-dependent).
Power Output (Version 5-6, GC8): 276 hp (206 kW) @ 6,500 rpm.
Power Output (Version 7, GDB): 276 hp (206 kW) @ 6,400 rpm.
Power Output (Version 8, GDB): 276 hp (206 kW) @ 6,400 rpm.
Power Output (Version 9, GDB Spec C): 315 hp (235 kW) @ 6,400 rpm.
Power Output (Version 10, GRB): 304 hp (227 kW) @ 6,400 rpm.
Max Torque (Version 5-6, GC8): 260 lb-ft (353 Nm) @ 4,000 rpm.
Max Torque (Version 7, GDB): 277 lb-ft (376 Nm) @ 4,400 rpm.
Max Torque (Version 8, GDB): 292 lb-ft (396 Nm) @ 4,400 rpm.
Max Torque (Version 9, GDB Spec C): 311 lb-ft (422 Nm) @ 4,400 rpm.
Max Torque (Version 10, GRB): 311 lb-ft (422 Nm) @ 4,400 rpm.
The EJ207 cylinder block is manufactured from cast
aluminum alloy, utilizing a semi-closed deck design. This configuration features
additional aluminum material surrounding the cylinder bores at the deck surface,
providing superior structural rigidity compared to open-deck designs while
retaining weight advantages over fully closed-deck configurations. The
semi-closed deck contributes to the engine’s ability to withstand high cylinder
pressures generated by elevated boost levels.
The horizontally opposed configuration places the cylinders in two banks of two,
with the crankshaft centered between them. Five main bearings support the
crankshaft, with the bearing caps integrated into the block structure. The
crankshaft is constructed from forged steel, cross-drilled for improved oiling,
and nitrided for surface hardness - features that contribute to its durability
at high engine speeds.
Forged pistons are utilized in Versions 7 through 9, providing increased
strength relative to cast pistons found in earlier iterations. The cylinder
bores are cast directly into the block and are finished with a precision-honed
surface. Oil galleries are drilled throughout the block to supply pressurized
lubricant to the crankshaft, connecting rods, and cylinder heads.
The cylinder heads are manufactured from cast aluminum
alloy, with separate heads for each cylinder bank. Each head incorporates dual
overhead camshafts, with the valvetrain utilizing shim-under-bucket tappets for
precise valve clearance control - a design chosen for its stability at high
engine speeds. The AVCS (Active Valve Control System) varies according to
version: Versions 7 through 9 employ single AVCS on the intake camshafts only,
while Version 10 (GRB/GVB) utilizes dual AVCS on both intake and exhaust
camshafts.
The AVCS system uses oil-pressure-actuated camshaft phasers to adjust timing
continuously based on engine operating conditions. The valves are arranged with
four valves per cylinder, with the intake valves measuring approximately 34.0 mm
(1.34 in) in diameter and the exhaust valves measuring approximately 30.0 mm
(1.18 in). The combustion chamber is a pent-roof design with centrally
positioned spark plugs. The intake ports are designed to generate tumble flow to
enhance air-fuel mixing under the forced induction conditions.
The fuel system utilizes sequential multipoint fuel
injection, with a fuel injector positioned at each intake port. The system
operates at a nominal fuel pressure of 3.5 bar (51 psi), regulated by a fuel
pressure regulator mounted on the fuel rail. Fuel is delivered from an in-tank
fuel pump through a filter and to the fuel rail, which is constructed from
stainless steel. The injectors are sequentially fired by the engine control unit
based on signals from the crankshaft position sensor and camshaft position
sensors.
The engine control unit calculates injector pulse width using inputs including
mass airflow, engine speed, throttle position, coolant temperature, and exhaust
oxygen sensor feedback. A hot-wire mass airflow sensor is located in the intake
tract upstream of the turbocharger. Later versions utilize a returnless fuel
system architecture to reduce fuel heating.
The lubrication system employs a wet-sump design with a
gear-type oil pump mounted within the front timing cover, driven directly by the
crankshaft. The pump incorporates a pressure relief valve to maintain consistent
oil pressure across the engine speed range. Oil is drawn from the sump through a
screened pickup tube and delivered through a full-flow spin-on oil filter
mounted on the cylinder block. The filtered oil is distributed through internal
galleries to the crankshaft main bearings, connecting rod bearings, camshaft
bearings, and the AVCS phasers.
The cross-drilled crankshaft ensures consistent oil supply to the connecting rod
bearings under high-rpm operation. A water-to-oil heat exchanger is integrated
into the system to maintain oil temperature within the optimal range. For
high-performance applications such as the Spec C models, a separate oil cooler
is incorporated. Total system capacity, including the filter and cooler, is 4.5
liters (4.8 qt).
The cooling system is a pressurized water-cooled design
utilizing a crossflow aluminum radiator with plastic end tanks, sized to manage
the thermal load of the turbocharged engine. A centrifugal water pump, driven by
the timing belt, circulates coolant through the cylinder block, cylinder heads,
and radiator. A wax-element thermostat is positioned in the coolant outlet
housing, with a nominal opening temperature of 76°C (169°F) for
performance-oriented calibration.
The system incorporates an expansion tank to accommodate coolant expansion and
to facilitate air removal. An electric cooling fan, controlled by the engine
control unit, provides airflow across the radiator. The cooling system is
designed to maintain consistent temperatures across the two cylinder banks, with
the turbocharger integrated into the coolant circuit to prevent oil coking after
engine shutdown. Coolant capacity is 7.0 liters (7.4 qt).
| Intake and Exhaust Systems |
Intake System: The intake system consists of an air
cleaner housing with a replaceable dry-type filter element, a hot-wire mass
airflow sensor, ducting to the turbocharger compressor inlet, the intercooler,
and the intake manifold. The intake manifold is constructed from cast aluminum
and is finished in the distinctive red color that identifies high-performance
Subaru engines. The manifold incorporates a variable-length intake system on
certain versions to optimize torque delivery.
Exhaust System: The exhaust system utilizes equal-length exhaust headers on
twin-scroll versions, with the headers merging into the turbocharger inlet. A
catalytic converter is positioned downstream of the turbocharger, with oxygen
sensors for closed-loop fuel control.
| Ignition and Electrical System |
Ignition System: The ignition system utilizes a
distributorless design with individual ignition coils mounted directly over each
spark plug in a coil-on-plug configuration. The engine control unit manages
ignition timing based on inputs including engine speed, load, and knock sensor
feedback.
Electrical System: The engine is equipped with a 12-volt electrical system. The
starter motor is mounted on the transmission housing. The alternator is
belt-driven from the crankshaft pulley.
The turbocharger configuration evolved over the
production run. Early versions (Versions 5-7) utilized single-scroll
turbochargers such as the IHI VF28, VF30, or VF34. Later versions (Versions
8-10) employed twin-scroll turbochargers including the VF36, VF37, VF42, and
VF53, paired with equal-length exhaust headers. The twin-scroll design separates
exhaust pulses to reduce interference, improving boost response and reducing
exhaust gas temperatures. An air-to-air intercooler is mounted atop the engine
in the characteristic Subaru configuration.
Overall Length: 670 mm (26.4 in)
Overall Width: 670 mm (26.4 in)
Overall Height: 590 mm (23.2 in)
Dry Weight (complete engine): 135 kg (298 lbs)
Engine Oil: Synthetic SAE 5W-30, 5W-40, or 10W-40
meeting API SN or higher.
Oil Capacity (with filter change): 4.5 L (4.8 qt).
Oil Change Interval: 5,000 km (3,100 mi) under severe conditions.
Oil Change Interval: 10,000 km (6,200 mi) under normal use.
Timing Belt Replacement Interval: 100,000 km (60,000 mi) or 5 years.
Spark Plug Type: NGK PFR7B or equivalent platinum-tipped plug.
Spark Plug Gap: 0.8 mm (0.031 in).
Spark Plug Change Interval: 60,000 km (37,000 mi).
Coolant Capacity: 7.0 L (7.4 qt).
Coolant Specification: Ethylene glycol-based antifreeze with corrosion
inhibitors.
Valve Clearance: Shim-under-bucket adjustment.
Intake Valve Clearance: 0.20-0.30 mm (0.008-0.012 in).
Exhaust Valve Clearance: 0.20-0.30 mm (0.008-0.012 in).
Engine Idle Speed: 750-800 rpm.
Tightening Torques (Critical Fasteners)
Connecting Rod Cap Bolts: 45 Nm (33 lb-ft) + 60° to 75° turn
Main Bearing Cap Bolts: 60 Nm (44 lb-ft) + 60° to 75° turn
Cylinder Head Bolts, Stage 1: 30 Nm (22 lb-ft)
Cylinder Head Bolts, Stage 2: 60 Nm (44 lb-ft) + 90°
Camshaft Bearing Caps: 10 Nm (7 lb-ft) for M6
Camshaft Bearing Caps: 20 Nm (15 lb-ft) for M8
Intake Manifold to Cylinder Head: 20 Nm (15 lb-ft)
Exhaust Manifold to Cylinder Head: 30 Nm (22 lb-ft)
Flywheel/Flexplate to Crankshaft: 80 Nm (59 lb-ft) + 90°
Spark Plugs: 25 Nm (18 lb-ft)
Turbocharger Mounting Nuts: 35 Nm (26 lb-ft)
Subaru Impreza WRX STi (GC8) 1998-2000: Version 5 and
Version 6 STi models for the Japanese domestic market.
Subaru Impreza WRX STi (GDB)
2000-2002: Version 7 (Bugeye) with single AVCS and VF30 turbocharger.
2002-2004: Version 8 (Blobeye) with single AVCS and VF34 or twin-scroll VF37
depending on variant.
2004-2007: Version 9 (Hawkeye) with single AVCS; Spec C models with twin-scroll
VF36 turbocharger and 320 ps output.
Subaru Impreza WRX STi (GRB/GVB) 2008-2014:
Version 10 with dual AVCS, twin-scroll turbocharger, and 9.0:1 compression
ratio.
Subaru WRX STi (VAB) 2014-2021: Final JDM
iterations of the EJ207 in the VA-chassis WRX STi.
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