CP Piston & Ring Set for Subaru EJ25 2.5RS - Bore (100mm) - Size (+0.5mm) - Compression Ratio (8.5)

This kit includes a set of four forged pistons and the necessary rings to match, specifically made for Subaru EJ25 engines. These pistons are designed to be 100mm in bore diameter, which is a +0.5mm oversize from the factory specification. They are engineered to achieve a compression ratio of 8.5:1, making them a solid choice for builds looking for a specific compression target.

CP Pistons is known for making well-built engine components, and these forged pistons are no exception. Forged pistons are stronger and more durable than cast pistons, which is important for engines that see harder use or higher performance demands. The +0.5mm oversize means these are intended for engines that have already been bored out to this dimension, typically during a rebuild or performance modification. This specific sizing and compression ratio are often chosen by builders aiming for a particular engine output or tuning profile.

When installing these pistons, ensure your engine block has been accurately machined to the 100mm bore size. It's also important to follow the manufacturer's recommended ring gap settings and lubrication procedures for optimal performance and longevity. Because these are an oversize part, proper machine work on the cylinders is critical for a good seal and to prevent premature wear.