Wiseco K598M9975AP Forged 99.75 mm Dish Pistons for Subaru EJ255 / EJ257

Vehicle Fitment

• Subaru Impreza WRX / STI (EJ257, 2.5 L 16V)
• Subaru Forester, Legacy, Outback with 2.5L DOHC Turbo (EJ255 / EJ257)

Features

• Forged from 2618 aluminum for high strength and durability
• ArmorGlide® skirt coating to reduce friction and increase longevity
• Dish-style crown with -19 cc volume for lower static compression
• Strutted forging for enhanced rigidity under load
• Anti-detonation groove to resist knock
• Forced-pin oiling to ensure reliable wrist-pin lubrication
• Includes pre-gapped ring set (9975VF) for easy installation
• Optimized for high-performance or turbocharged builds

Specifications

• Bore Diameter: 99.75 mm
• Compression Height: 30.70 mm
• Piston Dish Volume: -19.00 cc
• Static Compression Ratio: ~9.0:1
• Wrist Pin Diameter: 23.00 mm
• Piston Material: Forged 2618 Aluminum
• Approximate Piston Weight: ~382 g
• Ring Set: 9975VF (included)

Included Components

• 4x Forged Pistons
• 4x 23 mm Wrist Pins
• 1x Pre-gapped Ring Set (9975VF)
• 4x Circlips / Locks

Product Description

The Wiseco K598M9975AP is a high-performance forged piston kit crafted for Subaru's 2.5 L DOHC turbo engines, specifically for EJ255 and EJ257 applications. The 99.75 mm bore and -19 cc dish design provide a lower static compression ratio (~9.0:1), making this kit ideal for boosted or high-boost turbo builds.

Constructed from 2618 aluminum, these pistons are lightweight yet exceptionally durable. Their strutted forging structure gives added strength, while the ArmorGlide® coating helps minimize friction and wear. The built-in anti-detonation groove helps to improve combustion stability under demanding conditions.

This kit includes 23 mm floating wrist pins with forced-pin oiling for reliable lubrication, and the 9975VF ring set comes pre-gapped, making installation simpler. These pistons offer a dependable and race-ready foundation for high-power Subaru turbo setups.