EJ255/EJ257 ringland failure from detonation

Added 2026-10-26 · Updated 2026-10-26

Symptoms

A cylinder losing compression after detonation (the source describes the failure mode, not a symptom checklist).

Cause

A tuning shop's write-up says the EJ25 turbo engines' brittle hypereutectic pistons crack at the ringlands under detonation, from untuned modifications, low-octane fuel, heat soak or lugging the engine.

Fix (summary)

Prevention per the same source: a proper tune for any modifications, high-octane fuel, monitoring knock, and downshifting instead of lugging. A failed ringland means pistons, usually a rebuild. Single tuner source.

Related build entries

• Protect an EJ255/EJ257 from ringland failure

Other GE/GH/GR/GV problems

• Recalls 14V-311 and 14V-830: brake lines can corrode (salt states)
• Recall 19V-149: brake light switch can fail (2008-14 sedans incl. STI)
• Recall 19V-297: replacement ignition switch can slip to ACC
• Takata passenger air bag inflator recalls (2008-14)
• 5-speed crunches or grinds into 3rd as the synchro wears

More for this car

• All Subaru WRX and STI (GE/GH/GR/GV, 2008-2014) fitment answers · GE/GH/GR/GV common problems
• Newsletter archive: past issues with every new and corrected entry

Sources

• How to Avoid Ringland Failure in your Subaru WRX / STI — Come and Drive It (vendor article; read 2026-10-15; search excerpt only)
  EJ25x turbo pistons brittle; ringlands crack under detonation; tune, octane, avoid lugging.

Summaries are in our own words. Not repair instructions; consult the factory service manual.

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