Subaru EJ25 Turbo Engine | Legacy GT B4 Specs & Details

Description

🔧 Subaru Legacy GT B4 EJ25 Turbo Engine Overview

The EJ25 series engine, specifically the EJ255 and EJ257, powers the turbocharged Subaru Legacy GT B4 – a performance-oriented sedan combining luxury and rally-bred heritage. This 2.5L flat-four (Boxer) engine offers strong torque, responsive boost, and massive tuning potential.

🔍 Engine Specifications

• Engine Code: EJ255 or EJ257

• Displacement: 2.5L (2457cc)

• Configuration: Flat-4 (Boxer) DOHC, 16 valves

• Induction: Turbocharged (IHI VF-series or Mitsubishi TD04/TD05)

• Fuel System: Multi-point EFI

• Compression Ratio: 8.0–8.4:1 (depending on year)

• Power Output: ~250–265 hp (186–197 kW)

• Torque: ~340–350 Nm

• Intercooler: Top-mounted

• Emission Std.: Euro 3–4 depending on market/year

• Redline: 6500–7000 rpm

🚗 Applications

• Subaru Legacy GT B4 (2003–2009)

• Also found in:

  • Impreza WRX

  • Forester XT

  • Baja Turbo (US Market)

  • Outback XT

🏁 Performance & Reliability

The EJ25 is known for:

• Aggressive low-end torque

• Smooth power delivery from the turbo

• Iconic Boxer rumble (especially with UEL headers)

However, the EJ25 turbo has a mixed reliability reputation, mainly due to:

• Head gasket issues

• Rod bearing wear in tuned/high-mileage engines

• Ringland failure in poorly maintained or over-boosted engines

With proper oil changes, coolant system upkeep, and tuning care, the EJ25 can be a rewarding and robust engine.

🔧 Tuning Potential

• Stock internals can handle ~300–350 hp

• Popular upgrades include:

  • Bigger turbo (TD05H-18G, FP Green)

  • Front-mount intercoolers

  • ECU tuning (Cobb, EcuTek)

  • STI short blocks for added strength

📦 Aftermarket & Swaps

The EJ25 is widely supported by the aftermarket – parts, rebuild kits, and full crate motors are readily available. It’s also a favorite for engine swaps into lightweight Subaru chassis or track builds. Subaru EJ25 Turbo Engine

✅ Why Enthusiasts Love the EJ25:

• Legendary Boxer engine sound

• Turbocharged thrills with AWD grip

• Easily upgradeable with bolt-on mods

• Makes the Legacy GT B4 a sleeper sedan