Wiseco K598M100AP Forged 100.00 mm Pistons for Subaru EJ257 / WRX / STI (9.1:1)

Vehicle Fitment

• Subaru Impreza WRX / WRX STI (EJ257, EJ255 - 2.5L)
• Subaru Forester XT (2.5L DOHC)
• Subaru Legacy / Outback 2.5 Turbo (EJ25 16V)

Features

• Forged from high-strength 2618 aluminum alloy for maximum durability
• ArmorGlide® or ArmorPlating® skirt coating to reduce friction and resist scuffing
• Strutted forging design for high-load strength
• Dish (-19 cc) piston design for lower static compression, ideal for turbo setups
• Fully machined crown and anti-detonation groove for reliable combustion
• Forced-pin oiling to ensure consistent wrist-pin lubrication
• Includes high-performance ring set, pre-gapped for ease of installation
• Engineered for severe-duty and high-performance builds

Specifications

• Bore Diameter: 100.00 mm
• Compression Height: 30.70 mm
• Piston Dish Volume: -19.00 cc
• Compression Ratio: ~9.1:1 (some sources list 9.0:1 depending on head & gasket)
• Wrist Pin Diameter: 23.00 mm
• Piston Material: Forged 2618 aluminum alloy
• Approximate Piston Weight: ~385 g
• Ring Set: Included (10000XX or equivalent performance set)

Included Components

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

Product Description

The Wiseco **K598M100AP** is a high-performance forged piston kit designed for Subaru 2.5L turbo engines, such as the EJ257 found in WRX and STI models, as well as other turbocharged EJ25 variants. Built from aerospace-grade 2618 aluminum, these pistons combine strength and lightweight construction - making them ideal for high-stress, high-boost applications.

They feature a 100.00 mm bore, 30.70 mm compression height, and a -19 cc dish, which supports a static compression ratio of around **9.1:1**. This design is especially suitable for turbocharged engines that need a lower compression baseline for higher boost levels. The ArmorGlide® (or ArmorPlating®) skirt coating helps reduce friction and improve durability, while strutted forging enhances the piston's ability to withstand high loads. Forced-pin oiling ensures reliable lubrication to the 23 mm wrist pins.

The kit comes complete with a high-performance ring set that's pre-gapped, making installation more straightforward. Whether you're building a street-tuned turbo motor or a full race engine, the K598M100AP offers a robust and race-ready foundation.