The Subaru EJ257 Engine Issues – Reliability – Specifications and Tuning

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The Subaru EJ257 Engine Issues – Reliability – Specifications and Tuning. Einsteinerupload of. It is still used in the WRX STI models today. For good reason, many people adore these four-cylinder engines. Outside of the engine, the STI models have a lot to offer, but that’s beside the point. EJ257 engines produce 300 to 341 horsepower and 290-330 pound-feet of torque. Excellent performance for a 2.5L flat four boxer engine. This guide delves into the Subaru EJ257 engine, covering issues, reliability, specs, modifications, and more.

The Subaru EJ257 Engine Issues - Reliability - Specifications and Tuning

Subaru EJ257 Engine Specifications

The EJ257 flat-four boxer engine has the following specifications:

The Subaru EJ257 Engine Issues – Reliability – Specifications and Tuning

The EJ257 is distinguished by its flat four-cylinder design. This engine layout is used by only a few other manufacturers. It contributes to the distinct sound of many Subarus. In any case, the 2,457 cc displacement equals 2.5 liters. A turbocharger provides boost, allowing the EJ257 STi engines to deliver excellent performance for their size. Aluminum heads and blocks help to reduce weight.

Add to that its 16-valve DOHC, over-square design, and low compression ratio. All of these specifications put the Subaru EJ257 engines at 300-341 horsepower and 290-330 pound-feet of torque.

What Vehicles Make Use of the EJ257?

The 2.5 EJ257 engine is found primarily in the Impreza WRX STi and WRX STI models, so the list is fairly short. There are, however, a few exceptions. The EJ257 engine is available in the following models:

  • Impreza WRX STi 2004-2007 (300hp)
  • Impreza WRX STI 2008-2018 (305hp)
  • WRX STI from 2019 to the present (310hp)
  • 2019 STI S209 (341hp) (341hp)
  • Impreza WRX STi from 2005 to the present (276hp, non-US models)
  • Forester XT model years 2004-2005 (210hp)
  • Legacy GT / Outback XT 2005-2006 (250hp)

Subaru’s STI is the only model to be equipped with the EJ257 engine. However, the 2.5L STI engine was used in the Forester XT, Outback XT, and Legacy GT models. They were identical to the EJ257 engine except for the turbo, intercooler, and factory tune.

EJ257 2.5 Turbo Tuning and Modifications

Tuning and mods for the EJ257 will be covered in greater detail in a future article. However, we decided to go over some fundamentals in this article. The EJ257 engine’s problems and reliability are similar to those of the EJ255 WRX engine. This article will cover EJ257 issues, but in a shorter hand format than usual. As a result, we have some time to go over some tuning and mod information. Let’s get started.

The rally car heritage of Subaru WRX STI models is well known. The 2.5L flat-four turbo engine is the heart of these fun cars. 300+ horsepower from the factory is already quite impressive. A tune and a few basic mods/upgrades, on the other hand, can really take the STi EJ257 engine to the next level. Among these modifications are:

  • Tune
  • Intake
  • Exhaust system / Downpipe
  • Intercooler
  • Methanol Injection / Fueling (WMI)

Again, we’ll go over these mods in detail soon. Nonetheless, the modifications listed above can easily take the EJ257 2.5 turbo engine to a whole new level. Turbo upgrades are another popular way to push things even further. With deep pockets, the sky is the limit. But how does all of this relate to EJ257 engine problems and reliability?

Tuning and Reliability of the WRX STI

All else being equal, increasing boost and power will put more strain on the 2.5 flat-four engine. Internally, the EJ257 is not known to be the most powerful engine. With a good setup, they can be reliable on the stock engine. However, tuning and modifications are extremely common on Subaru WRX STI models. einsteineruploaded with.

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We’ll go over a few of these internal issues in the engine problems section. They can occur on completely stock vehicles. Many of these issues, however, are most common on modded EJ257 engines.

The point is that these engines are frequently tuned, modified, and upgraded. When done correctly, an EJ257 can be relied on in the long run. When you buy a used WRX STI, it’s not always clear what you’re getting. As a result, going that route can be a bit of a concern.

Subaru EJ257 Engine Issues

Among the most common issues with the Subaru EJ257 engine are:

  • Failure of the Turbocharger
  • Internal Issues
  • Oil Spills

Again, we discussed many of these concerns in an article about the WRX EJ255 engine. The EJ257 engine has similar problems, but there are some minor differences. In any case, we consider these to be the most common issues. That doesn’t necessarily imply that they’re widespread in the true sense of the word. Rather, these are some of the most common areas where Subaru EJ257 engine problems occur.

Having said that, the 2.5L STI flat four engine can deliver solid dependability and longevity. It’s not a bad engine, but some of the issues can be serious and costly. At the end of the article, we’ll return to the EJ257 reliability topic. Let’s move on and look at the failures listed above until then.

1) Turbo Failures in Subaru WRX STi

The first issue is usually caused by tuning and upgrading the EJ257 flat four engine. On stock engines, turbo failures can and do occur. This is particularly true of older EJ257 turbo engines. The engine has been in the WRX STI since 2004; however, age and mileage can take their toll on a turbo. As a result, some natural failures are simply the result of aging.

Tuning and modding the Subaru EJ257 engine, on the other hand. This usually necessitates increasing turbo boost pressure, which puts additional strain on the turbo. Unless you push things too far, it won’t kill the turbo right away. However, increasing boost can shorten the turbocharger’s lifespan on the STI.

With stock boost, it’s unusual for the turbo to fail before 125,000 miles. Add more and more boost, and the turbo will most likely fail. Some may last 100,000 miles or more. Other EJ257 turbos may fail before 50,000 miles. Although it is not a perfect science, the general point remains.

Symptoms of EJ257 Flat-Four Turbo Failure

The following symptoms could indicate a problem or failure with the 2.5L turbo:

  • The smoke produced by exhaust
  • Whining turbocharger
  • Power outage
  • Under-boosting

When turbos fail, they may start burning oil and emit smoke from the exhaust. When one of our BMWs blew its turbo, the engine spewed more than 5L of oil into the exhaust. That was a severe, unexpected failure, and it has nothing to do with longer-term turbo failures. Nonetheless, if a turbo isn’t working properly, it can burn/dump a lot of oil.

A problem with the EJ257 turbocharger can also be indicated by louder whining turbo sounds. Of course, a turbo in poor condition may not achieve the desired boost levels. This will result in significant power loss.

WRX STI Turbo Upgrade

Replacing a turbo is not a cheap job because they are expensive parts that require some labor. Used turbos can sometimes be found for less than $500, but this can be risky. einsteineruploading up to get together with. That’s also the starting point for most direct bolt-on turbo upgrades.

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Labor to replace the WRX STI turbo is typically in the $400-600 range, so factor that in. DIYers can save a lot of money here, but it’s a job for experienced mechanics. It’s a simple job if you know your way around the EJ257 engine.

The Subaru EJ257 Engine Issues - Reliability - Specifications and Tuning

2) Internal Engine Issues with the Subaru EJ257

Once again, this is one of the most common EJ257 issues on modded engines. Ringland issues are a hot topic, and some lawsuits have been filed as a result (along with other internal failures). It’s never fun to think about WRX STi engine failures, and we believe they’re exaggerated. However, EJ257 internal engine failures remain a significant issue.

With a tune and bolt-on mods, a good friend of ours blew up an EJ255 WRX and an EJ257 STI. We can safely assume he wasn’t an expert and made some mistakes, so we should take his failures with a grain of salt. However, it serves as a reminder that EJ engines aren’t the most forgiving. Small tuning errors, pushing things too far, and so on can have serious consequences.

In any case, the 2.5L flat-four engines have a number of failures. Among the most common are rods, rod bearings, pistons, and ringlands. The 2019+ WRX STI models have an updated piston design as well as some valvetrain upgrades. Time will tell if this helps to reduce the frequency of internal engine problems.

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Symptoms of an EJ257 2.5L Internal Problem

Internal engine failure symptoms on the Subaru EJ257 2.5 boxer engine include:

  • The smoke produced by exhaust
  • Loss of compression
  • Ticking / knocking
  • Oil pressure drop
  • Excessive use of oil

This is a very short list. When an engine fails or begins to fail, there are numerous possible symptoms. More oil can pass through the piston rings and ringlands, resulting in smoke and high oil pressure. Excessive oil consumption is a common symptom of rod bearings, among other things. Internal engine problems in the EJ257 can be indicated by knocking, pinging, or ticking sounds.

Internals/Engine Replacement for Subaru EJ257

Depending on the nature of the failure, you may be able to detect it in time. EJ257 rod bearing failures, for example, may not cause too much damage if detected early enough. Bearings must still be replaced, which can be costly. However, if a rod bearing fails completely, it can dig into the crank, causing rods to knock and pistons to slap on cylinder walls, among other things.

Internal problems can eventually lead to engine failure. Even if the engine can be rebuilt, the cost is likely to be the same or higher than installing a new, used engine. The point is that EJ257 engine failures are expensive.

3) EJ257 STI Oil Leak Trouble

Fortunately, the Subaru EJ257 does not have any major design flaws that cause oil leaks. However, it is a common problem with many cars and engines in general. We’re including this topic primarily because many WRX STI engines are 8 years or older.

Gaskets, seals, and rings are frequently made of rubber or rubber-like materials. They harden, crack, and develop small oil leaks over time. Oil leaks can deteriorate significantly over time. Among the most common EJ257 STI oil leaks are valve cover gaskets (VCG).

Other areas include oil pans and main seals, but valve cover gaskets appear to be much more common. Anyway, expect these leaks to appear after 8+ years and 100,000+ miles. Gasket failures can occur earlier, but this is usually due to age/mileage rather than a flaw.

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Symptoms of an Oil Leak in a Subaru EJ257

The following are some signs of oil leaks on the WRX STI:

  • There is a visible oil leak.
  • Smoking in the engine bay
  • Odor of burning oil
  • Spark plug holes clogged with oil
  • Oil scarcity

One of the most common and obvious symptoms is visible oil leaks. Not all oil leaks, however, result in oil dripping to the ground. The EJ257 oil leak may be minor enough that oil adheres to the block and other components. It may also drip onto hot parts and burn off, producing smoke and burning oil odors. This is typical of VCG leaks.

When changing spark plugs, keep an eye out for valve cover gasket leaks, which frequently result in oil getting into the spark plug chambers. Low oil levels, on the other hand, may indicate an oil leak. It’s unlikely that will be the first symptom you notice because an oil leak would have to be quite severe.

2.5-Four VCG Oil Leak Repair

einsteineruploading up to get together with. It takes a couple of hours or more to replace the valve cover gaskets on the Subaru 2.5L engine. As a result, a repair shop will most likely charge between $200 and $400.

It’s not a difficult DIY, but it’s critical that the gaskets seal properly. If not, you may find yourself doing the job again in a matter of weeks.

EJ257 Subaru Reliability

Is the engine in the Subaru WRX STI EJ257 dependable? We’d say the engine’s dependability is below average. It’s not so much that the 2.5L Subaru boxer engine is riddled with issues. However, the EJ257 suffers from a few serious and costly issues that occur more frequently than the average engine.

A large part of this is most likely due to the average WRX STi’s driving style, mods, and tuning. Many people purchase these vehicles and modify them. Not everyone is an expert, and the EJ257 can be temperamental. There are engines that can withstand a lot of abuse, errors, poor tuning, and so on. In our opinion, the Subaru EJ257 is not one of them.

Having said that, the EJ257 can be a dependable engine with average longevity. As with any engine, maintenance is critical. Use high-quality oils, monitor oil levels, and change fluids on a regular basis, among other things. If you intend to tune the WRX STI EJ257 engine, make sure it is properly setup and dialed in. When done correctly, the Subaru EJ257 can be a dependable and extremely enjoyable engine.