ZRP Forged Pistons for Subaru 2.5L EJ25 WRX-STi 99.75mm 8.5:1

Subaru EJ25 / EJ257 pistons are developed for moderate to high-level builds, primarily for street or club race cars aiming to develop their engine for high mileage and/or street use. Designed by ZRP engineers and manufactured in Germany from high-silicon, low-expansion 4032 (T6) alloy. This allows the engine builder to use a smaller piston-to-bore clearance, resulting in better sealing. This minimizes cold start knock noise, common in engines using forged pistons, providing quiet operation and low oil consumption. We have chosen a full round skirt design with a lower reinforcing band, with oversized and deeper valve pockets to allow for the use of high-lift camshaft profiles. They feature offset pins for quiet operation, and the piston pins are made from 9310 alloy. Other features include anti-detonation grooves to protect the top rings, a gas pressure accumulator groove for improved ring sealing, and vibration relief. Premium Japanese quality 1.00mm x 1.20mm x 2.80mm ring package included. Product Features & Design Anti-detonation grooves for increased lifespan and performance Gas pressure accumulator groove in the second ring land for increased lifespan. Horizontal grooves in the pin bore designed to allow oil into the piston pin area and pin bore. CNC precision machined ring grooves High-silicon/low-expansion 4032-T6 alloy Polished pin bores Side gas ports for improved ring sealing Full round skirt design with lower reinforcing band for high horsepower/supercharged applications Valve pockets designed to allow for oversized valves and high-lift camshafts Pistons designed to optimize compression for increased engine life and greater power potential Optional coatings offered upon request "Blast Off Bronze" thermal barrier coating Molybdenum side skirt and under-crown "Stealth Black" coating