CP Piston & Ring Set for Subaru EJ257 WRX STi – Bore (99.5mm) – Size (Standard) – CR (8.2)

SKU: SC7420-4 CP Piston &. Ring Set for 2004-2021 Subaru Impreza WRX STI EJ257 – Bore 99.5mm Standard – CR 8.2 This CP piston and ring set SC7420-4 delivers forged reliability for Subaru EJ257 turbo engines in 2004-2021 Impreza WRX STI models. The 99.5mm standard bore and 8.2:1 compression ratio handle aggressive boost levels up to 40 psi while ensuring durability in high-performance builds. Engine builders rely on this set for precise tolerances, weight matching, and consistent power in rally and drag applications. Key Features Forged 2618-T6 Aluminum: Delivers high strength-to-weight ratio to handle extreme cylinder pressures in turbocharged EJ257 engines 8.2:1 Compression Ratio: Supports safe high-boost operation up to 40 psi with lower detonation risk for reliable track performance Accumulator Grooves: Trap combustion residue to prevent ring flutter and maintain tight seal under high boost conditions Low-Friction Skirt Coating: Cuts drag, reduces operating temperatures, and prolongs piston life during aggressive shifts and launches Premium Rings and Pins Included: Pre-gapped rings with tool steel pins and clips for drop-in assembly and immediate competition use Product Notes Set includes 4 pistons, rings, wrist pins, and clips balanced to OEM specifications Designed for stock 79mm stroke rods and crankshaft in EJ257 engines Ships ready for professional engine assembly with CNC-machined precision Installation Notes Professional installation recommended. Hone cylinders to 99.5mm with CP-specific ra finish for optimal ring seating Compatible with OEM connecting rods and bearings This Part Fits Year Make Model Submodel 2004-2021 Subaru Impreza WRX STI 2007 Subaru Impreza WRX STI Limited 2011-2012 Subaru Impreza WRX STI Limited 2010 Subaru Impreza WRX STI Special Edition 2006-2009 Subaru Legacy GT 2.5XT 2008-2014 Subaru Forester XT Why Choose CP Pistons? Built in USA with motorsports heritage in rally and drag racing CNC-machined for exact bore fit and weight matching to OEM standards Engineered for Subaru EJ257 turbo platforms with proven high-boost handling Frequently Asked Questions Q: Will SC7420-4 fit all EJ257 engines in 2004-2021 STI? A: Yes, direct fit for standard 99.5mm bore EJ257 in Impreza WRX STI models including Limited and Special Edition plus Legacy GT and Forester XT Q: What material are these pistons made from? A: Forged 2618-T6 aircraft-grade aluminum with phosphate coating and moly skirt finish for heat resistance and low friction Q: What warranty covers this piston set? A: Backed by CP Pistons limited warranty against manufacturing defects when installed by certified builders Shipping & Handling Method: UPS Ground Availability: In stock – ships same or next business day Packaging: Foam-inserted box measuring 12 x 10 x 4 inches Weight: 5.8 lbs Reviews There are no reviews yet. Be the first to review “CP Piston & Ring Set for Subaru EJ257 WRX STi – Bore (99.5mm) – Size (Standard) – CR (8.2)” Cancel replyYour email address will not be published. Required fields are marked *Your rating * Rate… Perfect Good Average Not that bad Very poor Your review *Name * Email * Save my name, email, and website in this browser for the next time I comment.