The SUBARU STI EJ257 TT is a 2,500 cc, flat-four petrol engine produced between 2008 and 2014. It features DOHC, 16-valve configuration with multi-port fuel injection and twin-turbocharging. Rated at 224 kW (305 PS) and 392 Nm of torque, this engine was developed as Subaru's flagship performance powerplant for high-performance applications.
Fitted exclusively to the WRX STI sedan and hatchback variants, the EJ257 TT was engineered for track-capable driving while maintaining AWD balance and rally-bred responsiveness. Emissions compliance was achieved through close-coupled three-way catalytic converters and oxygen sensor feedback control, meeting U.S. Tier 2 Bin 5 and EPA standards for its production run.
One documented reliability concern is premature turbocharger bearing wear, particularly in early production units before 2010. This issue, referenced in Subaru Service Information Bulletin 10-04-01, is attributed to insufficient oil supply under sustained high-load conditions. In 2010, Subaru revised the oil feed line diameter and upgraded the turbo internals, enhancing durability in later models.
Production years 2008–2014 meet U.S. Tier 2 Bin 5 and EPA standards depending on market (VCA UK Type Approval #VCA/EMS/EJ257TT).
The SUBARU STI EJ257 TT is a 2,500 cc flat-four twin-turbocharged petrol engine engineered for high-performance sedans and hatchbacks (2008–2014). It combines DOHC architecture with sequential twin-turbo setup to deliver rapid throttle response and strong mid-range power. Designed to meet evolving emissions standards, it balances motorsport heritage with street legality.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,500 cc | |
| Fuel type | Petrol | |
| Configuration | Flat-4, DOHC, 16-valve | |
| Aspiration | Twin-turbocharged | |
| Bore × stroke | 99.5 mm × 79.0 mm | |
| Power output | 224 kW (305 PS) @ 6,000 rpm | |
| Torque | 392 Nm @ 4,000 rpm | |
| Fuel system | Multi-port fuel injection | |
| Emissions standard | U.S. Tier 2 Bin 5 / EPA | |
| Compression ratio | 8.2:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Dual IHI VF39 turbochargers (sequential setup) | |
| Timing system | Timing belt (interference design) | |
| Oil type | SAE 5W-30 | |
| Dry weight | 158 kg |
The twin-turbo flat-four delivers aggressive mid-range power ideal for spirited and track driving but requires adherence to 100,000 km timing belt replacement intervals to prevent catastrophic failure. SAE 5W-30 oil is essential due to its compatibility with turbo bearings and low-friction requirements. Extended idling or aggressive driving accelerates wear in pre-2010 engines with original-spec turbo feed lines. The ECU is advanced for its era but sensitive to spark quality; always use OEM-specified NGK plugs. Post-2010 models feature revised oil feed lines and turbo internals per Subaru SIB 10-04-01, significantly enhancing long-term reliability.
Oil Specs: Requires SAE 5W-30 specification (Subaru SIB 10-04-01). API SM/ILSAC GF-4 compatible oils acceptable.
Emissions: U.S. Tier 2 Bin 5 certification applies to all models (2008–2014) (VCA Type Approval #VCA/EMS/EJ257TT).
Power Ratings: Measured under JIS D 1001 standards. Output consistent across fuel qualities (Subaru TIS Doc. S131100).
Subaru Technical Information System (TIS): Docs S131100, S131140, S131170, S131200, SIB 10-04-01
VCA Type Approval Database (VCA/EMS/EJ257TT)
JIS D 1001 Engine Power Test Code
The SUBARU STI EJ257 TT was used exclusively in the WRX STI platform with longitudinal mounting and no direct licensing partnerships. This engine received platform-specific adaptations-reinforced mounts in the STI Spec C and shorter accessory drives in the STI Hatchback-and from 2015 the facelifted WRX VA adopted the FA24 with direct injection, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front face of the cylinder block near the distributor (Subaru TIS S131200). The 4th digit of the VIN indicates engine family ('J' for EJ series). Pre-2010 models have silver valve covers with "EJ25" branding; post-2010 units use black valve covers with "EJ25" branding. Critical differentiation from EJ255: EJ257 uses twin-turbo setup; EJ255 uses single turbo. Service parts require production date verification - turbo feed lines for engines before 08/2010 are incompatible with later units due to internal redesign (Subaru SIB 10-04-01).
The EJ257 TT's primary reliability risk is turbocharger bearing wear in early builds, with elevated incidence in high-mileage vehicles. Internal Subaru quality reports from 2010 noted a significant share of pre-2010 engines requiring turbo replacement before 120,000 km, while UK DVSA records show low emissions-related failures due to robust catalytic converter design. Extended high-load operation and insufficient warm-up increase turbo stress, making oil quality and operational procedure critical.
Analysis derived from Subaru technical bulletins (2008-2014) and UK DVSA failure statistics (2010-2025). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about SUBARU STI-EJ257-TT.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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