The EJ257 engine is the 2.5-liter turbocharged flat-four that powered the US-market Subaru WRX STI from the 2004 model year until the STI ended production after 2021. It belongs to Subaru’s long-running EJ family, which also includes the 2.0-liter EJ20 variants (EJ205, EJ207 and others) and the naturally aspirated and turbo 2.5-liter EJ25 variants such as the EJ253 and EJ255. If you are replacing a tired STI engine or planning a swap, the exact EJ code matters more than the displacement.
This guide explains what the codes mean, how the common versions differ, and what to check before you order a replacement.
How to read an EJ engine code
Every EJ engine is a horizontally opposed four-cylinder (a “boxer”). The first two digits after “EJ” give the displacement: EJ20 is 2.0 liters and EJ25 is 2.5 liters. The final digit identifies a specific version, which tells you about the heads, the induction, the market and the vehicle it came in. That last digit is why an EJ255 and an EJ257 are not interchangeable without planning, even though both are 2.5-liter turbo engines.
Codes also show up with letters, such as EJ20X and EJ20Y, which are Japanese-market 2.0-liter turbo versions from models such as the JDM Legacy GT. Imported engines are often listed by the US vehicle they are meant to replace, so read the listing closely. Always confirm the code stamped on the block and the vehicle it came from. Our guide to identifying your engine code by VIN explains how to find it on your car.
The EJ engines people search for most
| Code | Displacement | Induction | Commonly found in |
|---|---|---|---|
| EJ253 | 2.5L | Naturally aspirated, SOHC | Impreza, Legacy, Outback, Forester (non-turbo) |
| EJ205 | 2.0L | Turbo | US-market Impreza WRX of the early 2000s, Saab 9-2X Aero |
| EJ207 | 2.0L | Turbo | JDM Impreza WRX STI |
| EJ255 | 2.5L | Turbo | Later US WRX, Legacy GT, Forester XT |
| EJ257 | 2.5L | Turbo | US-market Impreza WRX STI |
Model-year ranges and fitment vary by market and trim, so treat this as a starting point and confirm against the listing and your vehicle’s documentation.
EJ20 engines: the 2.0-liter family
The EJ20 name covers several 2.0-liter engines. In the US, the EJ205 is best known from the first turbocharged Impreza WRX sold here. In Japan, the EJ207 powered the WRX STI and is known for revving freely. Imported engines are a popular route for swaps and replacements, and listings often pair them with a transmission, like this 2011-2014 Impreza WRX STI EJ207 engine with 6-speed transmission.
A JDM engine can be a good value, but it may use a different engine computer, wiring and sensors than the US car it is going into. Plan the electronics before you plan the install.
EJ25 engines: EJ253 and EJ255
The EJ253 is the workhorse naturally aspirated 2.5-liter found in a huge number of Imprezas, Legacys, Outbacks and Foresters. It is a common replacement-engine purchase when the original has failed. The EJ255 is the turbocharged 2.5-liter used in later US WRX models and in the Legacy GT and Forester XT. For example, the 2009-2013 Forester EJ255 2.5L turbo engine is the direct replacement for that model.
The EJ257 engine in the WRX STI
The EJ257 is the engine most STI owners mean when they talk about “the EJ.” It is a 2.5-liter turbo that differs from the EJ255 in its internal parts and turbo setup, and it was paired with the STI’s 6-speed manual and driver-controlled center differential (DCCD). It stayed in the US STI even after the regular WRX moved to Subaru’s newer FA-series engine for the 2015 model year.
The EJ257 has a reputation in the enthusiast community for being sensitive to tuning, oil condition and detonation. Owners commonly discuss ringland and rod bearing failures on modified or poorly maintained engines. That does not mean every EJ257 will fail, but it is a good reason to buy carefully, keep a conservative tune and maintain the oil. If you need a replacement, a matching unit such as the Impreza WRX STI EJ257 2.5L turbo engine keeps the swap simple.
Swapping between EJ versions
EJ engines share a lot of architecture, which is why swaps inside the family are common. A few things decide how easy a given swap will be:
- Engine computer and wiring. Different versions use different sensors, variable valve timing setups (AVCS, AVLS) and drive-by-wire or cable throttle. The engine computer must match the engine or be retuned.
- Turbo, intercooler and intake. Moving from non-turbo to turbo means adding the whole turbo system, the fuel system upgrade and the intercooler.
- Transmission. Turbo engines make more torque than many non-turbo transmissions were designed for. The STI 6-speed and the regular 5-speed are very different units.
- Emissions. Your state’s rules on engine swaps and emissions equipment apply. Check them before you start.
Our used engine buying checklist lists the questions to ask before you order, including mileage, compression and what accessories come with the engine.
Before you buy a replacement EJ
- Confirm your engine code and vehicle year, trim and market.
- Decide whether you want a long block or a complete engine with accessories.
- Check whether the listing includes the turbo, intake, wiring harness or engine computer.
- Plan new timing belt, water pump, seals and gaskets if they are not fresh.
- Have a plan for break-in and a careful first drive, especially on a turbo engine.
Finding Subaru EJ engines at TorqueHarbor
Browse our Subaru replacement engines or see every Subaru engine and part we list. If you want engine and gearbox together, check engine and transmission packages. For owner and maintenance information on your specific model, see Subaru of America.
Frequently asked questions
Which Subaru has the EJ257 engine?
In the US, the EJ257 powered the Impreza WRX STI and later the WRX STI from the 2004 model year until production ended after 2021. Confirm the code on your engine before ordering.
Can I put an EJ257 in a regular WRX?
People do, but it is a real project. Expect to deal with the engine computer, wiring, fuel system and possibly the transmission. Plan the whole swap and check your state’s emissions rules first.
What is the difference between the EJ255 and EJ257?
Both are 2.5-liter turbo EJ engines, but they differ in internal parts, turbo and tuning, and they came in different vehicles. They are not plug-and-play replacements for each other.
Is a JDM EJ20 a good replacement?
It can be a good value for the right project, but JDM engines often use different electronics than US cars. Confirm what is included and what your car needs before buying.
Start with the right reference 
Plan the arrival Always confirm the exact model, part number, condition and included components on the product listing. For a compatibility question, contact TorqueHarbor before ordering.