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Subaru CP Pistons STI Pistons for WRX EJ257

CP WRX Pistons

CP Forged STI pistons for the Subaru WRX EJ257 engine available on this page are are compatible with stock and oversized valves as well as stock and high lift camshafts. We have CP WRX pistons in several compression ratios and for use in many different cylinder bore sizes.

CP Carrillo products represent the highest quality and are engineered for maximum torque, power and durability. EJ257 Pistons can be ordered with optional gas ports, skirt coating, ceramic top coating, and stronger wrist pins if desired. To order a set with any of these options, please include a message in the note section of the order form during our check out process, or you may contact us in advance for more information regarding these optional features.

CP STI Piston Standard features include:

  • Deep valve reliefs accommodate high lift camshafts
  • Larger valve reliefs for +1mm valve sizes
  • Custom skirt cam and barrel design
  • Accumulator grooves
  • High strength aluminum forgings
  • High performance rings included
  • Fully CNC machined and balanced to +/- 1 gram
  • Wrist pins included at no additional cost
  • Double pin oilers force fed from oil ring groove
  • Pick lock grooves for easy lock removal
  • Pin fitting included

CP Pistons Subaru WRX Pistons and Ring Sets

For use in WRX STI and EJ257 engine equipped cars.

CP Pistons STI Pistons and Rings

  • Bore Size Cylinder bore size piston is designed to work in, listed in inches and millimeters
  • Relative Size Denotes whether this bore size is stock standard size, or an oversize listed in millimeters
  • CR Compression Ratio
  • Crankshaft Stroke Crank stroke the pistons are designed to work with. The stock stroke length is 79mm.
  • Connecting Rod Length Designed to work with stock connecting rod length of 130.5mm
  • Wrist Pin Diameter 23mm
  • Compression Height This is the distance from the centerline of the wrist pin bore to the top flat surface of the piston.
  • Ring Widths Ring grooves are machined to work with 1.0mm, 1.2mm, 2.8mm rings
  • WHAT’S INCLUDED 4 forged pistons, 4 Wrist Pins, pin retention locks and premium piston ring set


C.H. Compression Piston Set
3.9175 99.50 STD 79 130.5 1.208 8.2 SC7420

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3.927 99.75 +0.25mm 79 130.5 1.208 8.2 SC7422

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3.937 100.00 +0.5mm 79 130.5 1.208 8.2 SC7421

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3.957 100.50 +1.0mm 79 130.5 1.208 8.2 SC7423

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3.9175 99.50 STD 79 130.5 1.208 9.0 SC7425

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3.927 99.75 +0.25mm 79 130.5 1.208 9.0 SC7426

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3.937 100.00 +0.5mm 79 130.5 1.208 9.0 SC7427

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3.957 100.50 +1.0mm 79 130.5 1.208 9.0 SC7428

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3.9175 99.50 STD 79 130.5 1.208 10.0 SC7415

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3.927 99.75 +0.25mm 79 130.5 1.208 10.0 SC7416

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3.937 100.00 +0.5mm 79 130.5 1.208 10.0 SC7417

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3.957 100.50 +1.0mm 79 130.5 1.208 10.0 SC7418

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Our complete listing of all available CP Carrillo Pistons is on our site here CP Carrillo Forged Racing Pistons


Custom STI Pistons

If you do not see a shelf stocking part number Subaru STI piston set here with the specifications that you need, we can provide you with a set of custom pistons built to your exact requirements. Please contact us if you would like to discuss a set of CP customs and we will be happy to work with you to insure you get exactly the EJ257 WRX pistons that you require for your project.


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