EJ255 vs EJ257: Subaru Turbo Engines Compared, Plus JDM EJ20 Replacement Options

Your turbo EJ engine is finally done. Now you have a list of replacements and no clear answer on which one actually fits your car. This guide covers what sets the EJ255 and EJ257 apart, which vehicles use each, and when a JDM EJ20X or EJ20Y is a real option as a swap.

EJ255 and EJ257 at a Glance

Both are 2.5L horizontally opposed turbocharged four-cylinders from Subaru. Same architecture, different intent.

The EJ255 is a broad-range performance engine fitted across several models. The EJ257 is the STI-specific unit, built with more aggressive specs from the factory.

Which Subarus Have the EJ255?

Always cross-check your VIN with Subaru service data before ordering. Early model years sometimes have exceptions that catch buyers off guard.

Which Subarus Have the EJ257?

The EJ257 is STI-only in the US market. The WRX STI used it from 2004 through 2021. It was never factory-fitted to the standard WRX or Forester in the US. If someone is selling an EJ257 as a straight WRX replacement, that is a modified swap, not a factory fitment.

What Actually Differs, and Which Is Better?

The EJ257 runs stronger internals. It uses forged connecting rods, a more aggressive turbo, and dual AVCS in later variants. The heads are built to handle more heat and cylinder pressure. The EJ255 is not a weak engine. It is calibrated for a wider range of daily use across multiple platforms.

For a stock WRX or Forester XT replacement, the EJ255 is the right call. For an STI, the EJ257 is the correct engine. Swapping an EJ257 into a WRX is a popular mod but needs ECU changes and a tune. It is not bolt-in.

Is the EJ255 Reliable? Known Failure Points

Regular oil changes and not running the engine lean are the biggest things you can control. The EJ257 has its own concern: ringland damage under high boost on a poor tune. This is mostly a modified-build issue.

How Much Power Can They Take?

The EJ255 strains at higher boost levels on stock internals. The EJ257 handles more abuse thanks to forged rods, but the stock oiling system is still a weak point at serious power levels. Skip anyone giving a hard horsepower ceiling without citing a specific builder and a specific build. Numbers vary too much based on tune quality, fuel, and actual use.

JDM EJ20X and EJ20Y as EJ255 Replacements

JDM Seattle stocks EJ20X and EJ20Y engines listed as direct replacements for the EJ255. These are 2.0L Japanese-market turbocharged units from the same EJ family. They powered performance models in Japan equivalent to what the EJ255 covers in the US. Lower mileage is common because Japan’s regulations push cars out of service earlier.

EJ20X vs EJ20Y: Which One?

The EJ20Y is the more modern unit with dual AVCS and later donor vehicles. If you are replacing a later EJ255, the EJ20Y is the stronger match. JDM Seattle lists the JDM EJ20Y as a replacement sourced from 2008 to 2014 Impreza WRX and Forester applications.

What Has to Change

This is not a plug-and-play swap. Plan for these changes:

• ECU and tune: Your stock ECU is calibrated for the EJ255. The EJ20 needs a compatible ECU or a tune that accounts for the displacement and injector differences.

• Intake and turbo matching: Inlets and outlets may need adapting depending on your specific car and the donor unit.

• Wiring: Sensor connectors differ between JDM and USDM setups on some years.

• Emissions: Some states require OBD compliance and emissions testing. Check your state’s specific rules before committing.

• Clutch: If flywheel or clutch specs differ between the donor and your car, factor that cost in upfront.

Confirm with JDM Seattle what is included with their EJ20X or EJ20Y units before ordering, including turbo, intake, and ECU details.

JDM EJ20 vs JDM EJ255: Quick Compare

Transmission Pairing

The WRX runs the TY758 5-speed manual. The STI uses the TY856 6-speed. If you are swapping engines across model lines, your transmission situation matters. Browse Subaru transmissions at JDM Seattle to match the right unit for your build.

Buying a Used Turbo EJ Engine: Inspection Checklist

Before committing to any used EJ engine, check these:

• Compression and leak-down test results

• Turbo shaft play (minimal, no axial movement)

• Oil in charge pipes (a sign of seal wear)

• Oil pickup screen condition and debris

• Timing belt service history

• Mileage documentation (read JDM Seattle’s guide on how to verify a JDM engine’s mileage before you buy)

After install, follow a proper JDM engine break-in guide for the first 1,000 miles. Not sure whether to order a long block or a complete engine? Check JDM Seattle’s breakdown of long block vs complete engine before you decide.

EJ255 and EJ257 FAQs

What cars have the EJ255 engine?
The US WRX from 2008 to 2014, Forester XT from 2004 to 2008, and Legacy GT and Outback XT from 2005 to 2009. Always verify your specific year and trim with your VIN.

Which is better, the EJ255 or EJ257?
For STI replacements, the EJ257. For WRX, Forester XT, and Legacy GT, the EJ255 is the factory match. Putting an EJ257 into a non-STI car requires ECU and tune changes at minimum.

Is the EJ255 engine reliable?
Yes, with proper maintenance. Main failure points are ringland damage under high boost, rod bearings from oil starvation, and head gaskets. Consistent oil changes and a proper tune go a long way.

How much horsepower can an EJ255 handle?
There is no universal number. It depends on the build, tune, fuel, and supporting mods. Talk to a named Subaru builder with real results before setting a power target.

Can I put a JDM EJ20 in my WRX or Forester XT?
Yes, with supporting changes. Plan for ECU and tune work, possible wiring changes, and emissions compliance. JDM Seattle stocks the EJ20Y as a listed EJ255 replacement.

Can an EJ257 replace an EJ255?
It can bolt in with work, but it is a modified swap. ECU and tune changes are required. It is not a drop-in factory replacement for a WRX or Forester XT.

Replacing a WRX, STI, Forester XT or Legacy GT engine? Send JDM Seattle your VIN and transmission type and they will confirm whether an EJ255, JDM EJ257 or JDM EJ20 fits your car. Browse Subaru engines in stock.