JE Time Attack FSR Forged Piston Kit for Subaru EJ257 STI 100mm - 291062

JE Pistons | Time Attack FSR | Subaru EJ257 STI | 100mm Forged Pistons | 8.5:1 Compression | 2618 Aluminum | Set of 4

Rebuilding an EJ257 after piston damage, or putting together a Subaru STI engine that can handle a more demanding turbo setup? The JE Pistons Time Attack FSR Piston Kit, part number 291062, provides a performance-focused foundation for a properly engineered 2.5L Subaru boxer engine. Forged from high-strength 2618 aluminum, these pistons are designed for demanding street, track, turbocharged, and nitrous applications where factory-style internals may not match the goals of the build.

This kit features a 100.00mm bore, 8.5:1 nominal compression ratio, lightweight Forged Side Relief construction, accumulator grooves, precision wrist pin fit, and friction-reducing skirt coatings. The dished crown is designed around the EJ257 STI cylinder head and standard 79mm stroke configuration. Complete with JE Pro Seal rings, wrist pins, and retaining locks, this four-piston package gives engine builders the essential components for a carefully machined performance short block.

Key Features & Specifications:

Kit Includes:

• 4 x JE Time Attack FSR 2618 Forged Aluminum Pistons

• JE Pro Seal Piston Ring Set

• 4 x Case-Hardened Steel Wrist Pins

• Wrist Pin Retaining Locks

About the JE Time Attack FSR Subaru EJ257 Pistons

Built for Demanding Turbocharged Subaru Engines

Anyone who's spent time around modified Subaru EJ engines knows that rebuilding the bottom end isn't something you want to do twice. When you're increasing boost, repairing damaged internals, or building an STI for regular spirited driving and occasional track use, selecting the correct forged pistons is an important part of the process.

JE's Time Attack FSR pistons are designed around these demanding conditions. The 2618 forged aluminum construction offers the strength and ductility needed for high-cylinder-pressure applications, while the dished crown and 8.5:1 nominal compression configuration suit the intended EJ257 engine geometry.

Forged Side Relief Design

JE's proprietary FSR forging reduces skirt width to help lower piston friction and reciprocating mass. The design also accommodates a shorter wrist pin, saving additional weight while maintaining the structural characteristics required for performance operation.

At an average weight of 413 grams per piston, this set combines a substantial forged construction with a design focused on reducing unnecessary mass.

Accumulator Grooves and Ring Sealing

When combustion pressure rises, controlling the gases trapped between piston rings becomes increasingly important.

The accumulator groove provides additional space between the top and second rings, helping reduce inter-ring pressure and ring flutter. This supports more consistent top-ring sealing during demanding engine operation.

Skirt Coating and Precision Pin Fit

JE applies a skirt coating to reduce friction and wear between the piston skirt and cylinder wall. It also helps reduce operating noise, which can be especially useful when assembling an engine with forged 2618 pistons.

Precision-honed wrist pin bores provide controlled pin-to-piston clearance. JE identifies typical pin-fit clearances of 0.0003 to 0.0010 inches, with the final assembly measurements determined by the engine builder.

The included wrist pins, retaining locks, and JE Pro Seal piston rings complete the package for a properly prepared Subaru EJ257 short block.

Fitment & Installation Notes:

• Subaru STI EJ257: Designed for EJ257 2.5L turbocharged engine applications.

• Related Subaru EJ25 Builds: May be suitable for compatible EJ255/EJ257 configurations when the cylinder head, bore, stroke, connecting rods, and compression requirements match.

• Required Finished Bore: 100.00mm, representing a 0.50mm overbore compared with the standard 99.50mm EJ257 bore.

• Engine Stroke: Designed around the standard 79mm stroke.

• Connecting Rod Length: 130.5mm.

• Wrist Pin Diameter: 0.905 in.

• Compression Ratio: Nominal 8.5:1 with the intended engine geometry. Actual assembled compression depends on cylinder head volume, gasket thickness, deck clearance, and other components.

• Piston Configuration: -17.40cc dish with 1.209-inch compression height.

• Engine Machining: Cylinders must be properly measured and finished for the specified forged piston clearance.

• Ring Installation: Measure and set ring end gaps according to JE's instructions and the intended operating conditions.

• Valve Clearance: Verify piston-to-valve clearance, especially when using aftermarket camshafts, modified heads, or nonstandard timing components.

• Connecting Rod Compatibility: Verify wrist pin fit and the intended rod configuration before assembly.

• Engine Calibration: Fuel delivery, ignition timing, boost control, and supporting components must be matched to the completed engine build.

• Horsepower Rating: No fixed horsepower rating is specified for this piston set. Performance capability depends on the complete engine assembly and calibration.

Whether you're rebuilding a damaged STI engine or putting together a more capable EJ257 for spirited street use, time attack, drag racing, or other motorsport applications, the JE Pistons 291062 kit provides forged 2618 construction, lightweight FSR design, and purpose-built ring-sealing and friction-control features.