CP Piston & Ring Set for Subaru EJ257 WRX STI- Bore (99.75mm) - Size (+0.25) - CR (8.5) - Set of 4

If you're rebuilding the engine in your 2004-2012 Subaru Impreza WRX or STI, especially for a performance build, a solid set of pistons is crucial. This set from CP Pistons is designed specifically for the EJ257 engine, offering a 99.75mm bore with a +0.25mm oversize and a compression ratio of 8.5:1. This setup is ideal for those looking to tune their engine for increased power while maintaining reliability.

CP Pistons are well-known in the performance world for their strong construction. These pistons are forged, meaning they start as a solid block of aluminum that's heated and hammered into shape under immense pressure. This process creates a much denser, stronger, and more durable piston than cast alternatives, which is essential when dealing with the higher cylinder pressures found in modified or performance-tuned engines. The 8.5:1 compression ratio is a smart choice for builds that will use forced induction, like turbochargers, as it provides ample room for boost without excessive detonation risk. This set includes all four pistons and their corresponding rings, ready for installation.

When installing these pistons, ensure your cylinder bores are properly honed to match the +0.25mm size and that you follow the manufacturer's recommended piston-to-wall clearance for optimal performance and longevity. This set is a key component for anyone serious about building a robust EJ257 engine.