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When it comes to choosing a Subaru engine for your vehicle or your next build, understanding the differences between the EJ255 vs EJ257 is essential. While these two engines share a lot of similarities, they have some important differences that can influence which is the better choice for your needs. Whether you're looking for reliability, performance, or modding potential, this guide will help you make an informed decision.
Similarities Between The EJ255 And EJ257
Before diving into the differences, let’s start with what makes these engines similar. Both the EJ255 vs EJ257 block are nearly identical, which is why you’ll often see conflicting information about these engines.
Core Similarities:
- Boxer Design: Both engines are 2.5-liter, turbocharged, flat-four (boxer) engines, providing Subaru's signature low center of gravity and excellent weight distribution.
- Semi-Closed Deck: The semi-closed deck design ensures durability and strength, especially under higher boost levels.
- Shared Components: Most model years of the EJ255 and EJ257 share the same case, crankshaft, camshafts, and rods.
Despite these shared features, key differences in internals and performance set these engines apart.
Key Difference In Engine Specifications
When comparing the EJ257 vs EJ255, the specifications and internals play a huge role in deciding which engine is better suited for your goals.
Pistons and Heads
- EJ255: Equipped with smaller turbos and pistons that prioritize efficiency and affordability. This engine delivers up to 265 horsepower and 258 lb.-ft. of torque from the factory.
- EJ257: Designed for higher performance, it features larger turbos, pistons, and intercoolers to handle more boost and power. Factory specs range up to 341 horsepower and 330 lb.-ft. of torque, particularly in Subaru STI models.
Active Valve Control System (AVCS)
- Both engines feature Subaru’s AVCS technology for variable valve timing. However:
- EJ255: Employs single AVCS on the intake camshafts.
- EJ257: Models from 2008 onward feature AVCS on both intake and exhaust camshafts, providing better efficiency and performance.
Verdict: The EJ257 offers more power and advanced features, making it the better choice for performance enthusiasts, while the EJ255 provides a more budget-friendly and reliable alternative.
Reliability and Longevity
Both engines are renowned for their reliability, but like any engine, proper maintenance is key. With the right care, both the EJ255 and EJ257 can surpass 250,000 miles. However, each engine has some common issues to watch for.
Rod Bearing Failure
- Cause: Lack of oil or dirty oil can lead to rod bearing failure.
- Prevention: Regular oil changes and ensuring proper lubrication are essential.
- Notable Differences: The EJ257 can handle more boost than the EJ255, making it a slightly better platform for modification without risking rod bearing failure.
Ringland Problems
- Both engines are prone to ringland failure, where cracks in the piston’s compression rings can lead to reduced compression and engine damage. This issue is common under high boost or with aggressive modifications.
Turbocharger Issues
- EJ255: Prone to turbo failure due to small oil filters that can clog and restrict oil flow to the turbo.
- EJ257: While it’s also not immune to turbo issues, its larger turbos and intercoolers make it more robust under pressure.
Oil Leaks
- Both engines may develop oil leaks around the valve cover gaskets after 100,000 miles. Addressing these leaks promptly is crucial to prevent further engine damage.
Verdict: While both engines are reliable with proper care, the EJ257’s stronger internals and higher tolerance for boost make it better suited for high-performance builds.
Modding Potential: Which Engine Offers More?
If you're planning to modify your Subaru for increased power, the EJ257 vs EJ255 comparison is critical. Both engines are mod-friendly, but the EJ257 is the superior platform for high-performance upgrades.
EJ255 Modding
- Responds well to basic modifications, such as upgraded intakes, exhaust systems, and ECU tuning.
- Limited by its smaller turbos, intercoolers, and weaker internal components, making it less ideal for handling high levels of boost.
EJ257 Modding
- Built for performance with larger turbos, intercoolers, and high-flow heads.
- Dual AVCS on newer models provides better tuning potential and more efficient airflow.
- Capable of safely handling higher boost levels, making it the preferred choice for track builds and high-horsepower applications.
Verdict: While the EJ255 is a solid choice for moderate modifications, the EJ257 offers far more potential for serious power upgrades.
EJ255 vs EJ257: Final Thoughts
When deciding between the EJ255 vs EJ257, consider the following:
- Budget: The EJ255 is more affordable and still delivers reliable performance for daily drivers and moderate builds.
- Performance Goals: For high-performance applications, the EJ257 is the better choice due to its stronger internals and higher power output.
- Modding Potential: If you plan to heavily modify your engine, the EJ257 offers greater flexibility and durability.
Both engines are excellent choices, but your decision should align with your specific goals and budget. Whichever you choose, proper maintenance and thoughtful modifications will ensure years of reliable performance.
Shop Subaru Engine Parts At JEGS
Whether you’re building around an EJ255 or EJ257, JEGS has all the parts you need to make your Subaru perform at its best. From turbos and intercoolers to pistons and performance upgrades, we’ve got you covered.
Shop online at JEGS.com or call us at 1-800-345-4545 for expert advice on selecting the right parts for your Subaru. Let JEGS help you achieve your performance goals!
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