CP Piston & Ring Set for Subaru EJ257 WRX STI- Bore (99.75mm)-Size (+0.25mm)- CR (9.0) - Set of 4

If you're rebuilding the engine in your 2004-2012 Subaru Impreza WRX or STI, especially one that's seen some hard miles or is being prepped for more power, a solid set of pistons is key. This set from CP Pistons is built for the EJ257 engine, offering a 99.75mm bore, which is a +0.25mm oversize from stock, and a 9.0:1 compression ratio. This makes them a strong choice for builds aiming for improved performance while maintaining reliable operation.

CP Pistons are well-known for their forged construction, using high-strength aluminum alloys that can handle the increased cylinder pressures and temperatures that come with performance tuning or heavy-duty use. These pistons are designed to be a direct fit for the EJ257, meaning they'll work with your existing connecting rods and crankshaft, simplifying the rebuild process. The included rings are matched to the pistons to ensure proper sealing and oil control, which is critical for engine longevity and performance. The 9.0:1 compression ratio is a good balance, allowing for good power output without being overly sensitive to fuel quality, though premium fuel is always recommended for tuned EJ257s.

When undertaking an engine rebuild of this caliber, it's important to ensure all components are clean and properly lubricated during assembly. This set includes the four pistons and their corresponding rings, ready for installation. Remember that this kit is not CARB approved and cannot be shipped to California. Always refer to the manufacturer's detailed installation instructions for proper assembly and break-in procedures.