If you own a Subaru WRX or STI, or you're shopping for a replacement engine, you've seen these two codes: EJ255 and EJ257. They're both turbocharged 2.5L horizontally-opposed four-cylinders from Subaru's EJ family — but they're built to different specifications, and using the wrong code for your chassis can create real problems. Here's everything you need to know. This post is part of our JDM engine codes guide.
The essential difference
Both the EJ255 and EJ257 are 2.5L turbocharged boxers. The EJ257 is the performance-focused, higher-output variant used in the STI; the EJ255 is the WRX/Legacy GT/Forester XT code, designed for more moderate boost and street use. Internally, the EJ257 uses forged internals and a closed-deck block design; the EJ255 uses cast pistons and an open-deck block.
Specs comparison
| Spec | EJ255 | EJ257 |
|---|---|---|
| Applications | WRX, Legacy GT, Forester XT | WRX STI (all years) |
| Block design | Open-deck | Semi-closed deck |
| Pistons | Cast | Forged |
| Factory output (approx.) | 224–230 hp (market/year varies) | 293–305 hp (STI spec) |
| Boost tolerance | Moderate; open deck limits max boost headroom | Higher; closed deck handles more sustained boost |
Why the open-deck vs closed-deck distinction matters
The deck is the area at the top of the cylinder block where the head gasket seats. An open-deck design has cooling passages that open to the outside of the cylinder bore — better for heat management at stock boost levels, but structurally weaker when you start raising boost significantly. The EJ255's open-deck block is a real limit when pushing power above ~300 hp; the EJ257's semi-closed deck handles higher boost loads without the cylinder wall distortion risk.
Can you swap an EJ257 into a WRX?
Yes, and it's a well-documented upgrade path — but it's not a simple drop-in. The STI uses a different ECU, a different TMIC (top-mount intercooler) arrangement, and a 6-speed transmission rather than the WRX's 5-speed. You can run an EJ257 in a WRX chassis, but you'll need to either use the STI management system or have the engine tuned properly for your WRX setup. Many builders go this route specifically to get the forged internals into a WRX platform.
Current pricing from our inventory
The pricing gap between these two codes is significant: EJ255 engines from our current stock run $999–$1,299 (median ~$999), while EJ257 units run approximately $4,899 — reflecting the STI-spec forged internals and the higher demand for performance-oriented Subaru power. See our cost guide for context on Subaru engine pricing overall.
What about FA20DIT and FA24?
The newer WRX (2015+) moved to the FA20DIT (2.0L direct-injection turbo boxer), and the current-generation WRX uses the FA24 (2.4L). These are a different engine family entirely — see our current listings for FA20DIT and FA24 if those are relevant to your chassis.
Frequently asked questions
My WRX uses an EJ255 — should I just replace it with another EJ255?
For a like-for-like replacement on a stock or mildly modified WRX, yes — matching the original code keeps your ECU and drivetrain pairing straightforward. If you're planning significant power increases, the EJ257 swap becomes worth evaluating.
Are EJ257 engines more reliable than EJ255?
At stock power levels, both are comparable in service life. The EJ257's forged internals make it more tolerant of power increases, but it has the same fundamental Subaru EJ-family characteristics (head gasket sensitivity at high mileage, for example) as the EJ255.
What year EJ257 should I look for?
The EJ257 saw continuous development through the STI's production run. Later units (post-2008) are generally considered refinements of the earlier design. Confirm which year's specification you're getting when buying.
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