CP Piston & Ring Set for Subaru EJ257 WRX STI- Bore (100.0mm)-Size (+0.5mm)- CR (10.0) - Set of 4

CP Pistons is well-known for making strong internal engine components, and this piston and ring set is a prime example of their work for performance Subaru builds. This set is specifically designed for the 2004-2012 Subaru Impreza WRX STI with the EJ257 engine. It features a 100.0mm bore and is a +0.5mm oversize, meaning it's intended for engines that have been bored out to this specific dimension during a rebuild. The compression ratio is set at 10.0:1, which is a common target for modified EJ257 engines looking for improved performance without going too extreme.

These pistons are forged, which means they start as a solid block of aluminum that's heated and hammered into shape. This process creates a much stronger and more durable piston than cast ones, making them ideal for engines that see higher cylinder pressures and temperatures from modifications like turbo upgrades or performance tuning. The set includes all four pistons and the necessary rings, ready for installation. It's important to note that these pistons are not CARB approved and cannot be shipped to California.

When rebuilding your EJ257, using a well-built piston set like this from CP Pistons ensures you're starting with a solid foundation. Make sure your machine shop has bored your cylinders precisely to the 100.0mm specification for a proper fit. This set is a critical component for anyone looking to refresh or significantly upgrade their Subaru's engine internals.