CP Pistons EJ257 WRX STI
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CP Pistons for EJ257 WRX STI Engines
Available in:
- Bore: 99.5mm (STD) / Comp: 8.2:1 - Part#: SC7420
- Bore: 99.75mm (+0.25mm) / Comp: 8.2:1 - Part#: SC7421
- Bore: 100mm (+0.5mm) / Comp: 8.2:1 - Part#: SC7422
- Bore: 100.5mm (+1mm) / Comp: 8.2:1 - Part#: SC7423
- Bore: 99.5mm (STD) / Comp: 9.0:1 - Part#: SC7425
- Bore: 99.75mm (+0.25mm) / Comp: 9.0:1 - Part#: SC7426
- Bore: 100mm (+0.5mm) / Comp: 9.0:1 - Part#: SC7427
- Bore: 100.5mm (+1mm) / Comp: 9.0:1 - Part#: SC7428
- Bore: 99.5mm (STD) / Comp: 10.0:1 - Part#: SC7415
- Bore: 99.75mm (+0.25mm) / Comp: 10.0:1 - Part#: SC7416
- Bore: 100mm (+0.5mm) / Comp: 10.0:1 - Part#: SC7417
- Bore: 100.5mm (+1mm) / Comp: 10.0:1 - Part#: SC7418
STD bore size pistons are not recommended in a used bore for any performance engine unless the bores have done minimal work with minimal wear and the correct piston to bore clearance can be adhered to.
All piston manufacturers have a specific piston to bore clearance that they recommend. If STD bore pistons are requested and there is a piston to bore clearance issue we will not exchange or refund, due to the reasons given above.
| Product Name | CP Pistons EJ257 WRX STI |
|---|---|
| Brands | CP Carrillo |
| Engine | EJ257 WRX STI |
| Make | Subaru |
Delivery & Freight
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What information do I need to match these pistons to my engine?
You need the engine code, bore size, stroke, rod length, pin diameter and target compression ratio. These determine the correct piston compression height and crown design.
How should ring gaps be set for these pistons?
Ring gaps must be set by your engine builder based on fuel type, boost level and the intended rpm range. Forced-induction engines usually require larger gaps.
Are forged pistons suitable for street engines?
Yes. Forged pistons handle detonation and high cylinder pressure better than cast units. Your builder should set the piston-to-bore clearance to suit your application.
What bore sizes are available for the CP Pistons EJ257 WRX STI?
The CP Pistons for EJ257 WRX STI are available in multiple bore sizes: 99.5mm (STD), 99.75mm (+0.25mm), 100mm (+0.5mm), and 100.5mm (+1mm). Each bore size is offered with different compression ratios of 8.2:1, 9.0:1, and 10.0:1.
What is the recommended clearance for these pistons?
Each piston manufacturer has specific recommendations for piston to bore clearance. It is crucial to adhere to these specifications to ensure optimal performance and reliability. For STD bore pistons, they should only be used in bores with minimal wear and the correct clearance.
Do the CP Pistons EJ257 come with locks?
No, the CP Pistons EJ257 WRX STI are supplied without locks. You will need to use the factory locks that are compatible with your engine.
Can I use the STD bore size pistons in a used bore?
Using STD bore size pistons in a used bore is not recommended unless the bores have minimal wear and can maintain the correct piston to bore clearance. If there are clearance issues, we cannot offer exchanges or refunds.
What should I consider when selecting the compression ratio for these pistons?
When selecting a compression ratio for the CP Pistons EJ257, consider your engine's intended use, fuel quality, and tuning setup. Higher compression ratios can provide more power but may require higher octane fuel and careful tuning to avoid knock.
