The EJ257 is Subaru’s 2.5-liter (2,457 cc) turbocharged, intercooled flat-four, used in the US WRX STI from 2004 through 2021. It has double overhead cams, four valves per cylinder, a 99.5 mm bore and 79.0 mm stroke, and the 1-3-2-4 firing order shared by Subaru’s four-cylinder boxers. The STI’s rating rose from 300 hp in the early cars to about 305 hp and then 310 hp in the final years, with torque around 290 to 300 lb-ft.
EJ257 specs
| Spec | Value |
|---|---|
| Configuration | Flat-four (boxer), DOHC, 16 valves, turbocharged |
| Displacement | 2.5 L (2,457 cc) |
| Bore x stroke | 99.5 x 79.0 mm |
| Firing order | 1-3-2-4 |
| US WRX STI rating | About 300 hp (early) to 305 to 310 hp (later), by year |
| Used in | WRX STI (US) 2004 to 2021 |
EJ257 vs EJ255
The EJ255 is the related 2.5-liter turbo engine used in the WRX, Forester XT and Legacy GT, with a different turbo and lower output. The two share the basic block family but differ in heads, turbos and internals; see EJ255 vs EJ257.
EJ257 specs by era
Subaru revised the EJ257 several times over its long run, including changes to the cylinder heads, valve timing system, turbo and engine management. Parts are not always interchangeable across years, so check fitment by year when replacing heads, turbos or a short block. The US STI used the EJ257 for its entire run, while some markets used other versions.
Turbo and intercooling
The EJ257 uses a top-mounted intercooler fed by the hood scoop. Turbo and boost details vary by year; see what does an intercooler do? and what does a wastegate do?
Known weak points
The EJ257 is durable when maintained, but its pistons’ ringlands and the rod bearings are the common failure points when the engine sees detonation, low oil or excessive boost; see EJ257 problems and Subaru head gasket and ringland failures. A timing belt drives the cams, so the change interval matters; see timing belt.
Built blocks
Many owners replace a failed EJ257 with a built short block using forged pistons; see forged vs cast pistons and closed deck vs open deck. We list options such as the Turn In Concepts Stage 3+2 EJ257 short block at $6,799.00; see all Subaru EJ25 engines.
Oil and fuel
Use the oil grade in your manual and check the level often, because low oil is a leading cause of EJ257 bearing failures. Premium fuel is required to avoid knock under boost.
Related
See WRX vs STI, WRX generations and how long a Subaru engine lasts.
More guides: FA20 vs EJ25 · Subaru oil pickup tube.
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