Wiseco K598M9975 Forged 99.75 mm Dish Pistons for Subaru EJ255 / EJ257

Vehicle Fitment

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

Features

• Forged from high-strength 2618 aluminum alloy
• ArmorGlide® skirt coating to reduce friction and resist seizure
• "Dish" piston design with -19.0 cc volume for lower compression
• Strutted forging for enhanced rigidity and strength
• Anti-detonation groove to mitigate knock risk
• Forced-pin oiling to ensure reliable lubrication of the wrist pin
• Includes pre-gapped high-performance ring set (9975VF)
• Optimized for turbocharged, high-performance or race builds

Specifications

• Bore Diameter: 99.75 mm
• Compression Height: 30.70 mm
• Piston Dish Volume: -19.00 cc
• Compression Ratio: ~9.0 : 1
• Wrist Pin Diameter: 23.00 mm
• Piston Material: Forged 2618 Aluminum
• Piston Weight (nominal): ~382 g
• Included Ring Set: 9975VF
• Stroke (engine): ~79.00 mm

Included Components

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

Product Description

The **Wiseco K598M9975** is a professional-grade forged piston kit designed for high-performance Subaru 2.5L turbo engines, particularly the EJ255 and EJ257. With a 99.75 mm bore and a -19 cc dish design, these pistons are engineered to provide a low static compression ratio (~9.0:1), making them ideal for turbo or high-boost setups.

Built from 2618 forging, the pistons combine strength and lightweight performance. The ArmorGlide skirt coating reduces friction and improves longevity, while the strutted forging structure adds mechanical strength under high load. The anti-detonation groove further helps to mitigate knocking, ensuring reliability in demanding performance scenarios.

This kit comes with 23 mm wrist pins and a pre-gapped 9975VF ring set to simplify installation and ensure reliable sealing. Whether you're building a street-tuned WRX/STI or a race-spec turbo motor, these Wiseco pistons provide a robust, durable foundation.