Wiseco Piston Kit Subaru Impreza RS-EJ25 DOHC 2.5L 16V (BOD)
Wiseco US-K599M9975 – Forged Piston Set Subaru EJ25 2.5L DOHC
The Wiseco US-K599M9975 set is a specialized solution designed for demanding applications based on the Subaru EJ25 engine. These pistons are engineered for maximum strength and precise combustion control under high boost and elevated RPM, making them an ideal choice for motorsport, tuning, and aggressive street performance builds.
Key Features
Forged from 2618 aluminum – optimized for durability to withstand high pressures, temperatures, and mechanical stresses.
Precisely contoured piston crown – a dished design resistant to detonation, tailored for high-performance applications, providing a compression ratio of 8.7:1.
ArmorGlide® coated skirts – a specialized low-friction coating that reduces cold start noise and friction, while enhancing cylinder longevity.
Floating wrist pin – thick-walled, full-floating 22.99 mm (0.9055") wrist pin offers reliability under high power and RPM conditions.
Dedicated piston ring set included – optimized ring profiles and tensions suited for turbocharged engines and high-performance fuels.
Forced pin oiling – wrist pin lubrication via ring oil groove improves durability under extreme operating conditions.
Typical Applications
Performance Subaru EJ25 builds (Impreza WRX STI, Legacy, Forester, etc.)
Engines modified for turbocharging, motorsport, and other high-demand scenarios
Drag, drift, time attack, and street/strip applications with power levels well beyond stock parameters
Technical Specifications
| Parameter | Value |
|---|---|
| Cylinder bore (bore) | 99.75 mm (3.927") |
| Compression height (CH) | 30.25 mm |
| Compression ratio | 8.7:1 (dished volume −23.00 cc)* |
| Material | Forged 2618 aluminum |
| Wrist pin | Ø 22.99 mm (0.9055") full-floating |
| Ring grooves | 1.2 / 1.5 / 2.0 mm |
| Quantity per set | 4 pistons |
| Piston ring set included | Yes |
| Application | Subaru EJ25 2.5L DOHC |
*Measured with standard combustion chamber volume.
Kit Contents
4 × Wiseco US-K599M9975 forged pistons
4 × full-floating wrist pins (0.9055")
Complete set of piston rings
Wrist pin locks
Installation instructions and recommendations
Installation Notes
Piston-to-cylinder clearance per Wiseco’s specifications (minimum 0.10 mm recommended for street use)
Verify valve clearance for higher cam lifts
Adjust ring end gaps according to power level and boost pressure
Use high-ZDDP oils in builds exceeding 500 HP for optimal protection
Wiseco US-K599M9975 – forged pistons built for those who demand a truly strong and reliable Subaru EJ25 engine!