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FA20DIT vs EJ257

Chandler Stark

Meet Chandler

Chandler is an automotive expert with over a decade of experience working on and modifying cars. A couple of his favorites were his heavily modded 2016 Subaru WRX and his current 2020 VW Golf GTI. He’s also a big fan of American Muscle and automotive history. Chandler’s passion and knowledge of the automotive industry help him deliver high-quality, insightful content to TuningPro readers.

The FA20DIT and EJ257 are two of the most popular performance engines that Subaru has ever produced. The EJ257 is one of the most iconic and legendary tuner engines of all time. It powered every iteration of the STi in North America from 2004 on, and was perennially one of the top performance options on the market. The FA20 came along in 2012 and found its way into the Subaru WRX in 2015, where it gained its own reputation for delivering outstanding performance with great tunability.

Both boxer engines met their demise in 2021 when Subaru announced that both were ending production. The FA20 still lives on in the larger displacement FA24, but the EJ series is now discontinued in North America. It’s unfortunate, because both of these engines are absolutely fantastic. They were plenty powerful from the factory, and they both still have immense amounts of aftermarket support. Both engines suffer from some unfortunate defects, but overall are relatively reliable.

For many enthusiasts, the burgeoning questioning over the past few years has been: which is better, the FA20 or the EJ257? This guide will cover everything you need to know about both engines, and will look at design, reliability, and most importantly, performance and upgrades. Let’s get started!

Subaru FA20DIT vs EJ257 - FA20 & EJ257 Specs, Upgrades, Reliability

Engine Comparrison Specs

Years in production2012-20212004-2021
ConfigurationFlat 4 (Boxer)Flat 4 (Boxer)
Valve Train16V DOHC16V DOHC
Turbo DesignTwin-scroll TurboSingle-scroll Turbo
Displacement2.0 L (1,998 cc)2.5 L (2,457 cc)
Fuel SystemDirect InjectionFuel Injection
Head/Block MaterialAluminumAluminum
Bore & Stroke86mm x 86mm99.5mm x 79mm
Boost Pressure15.9 PSI14.5 PSI
Horsepower Output250-296 hp300-341 hp
Torque Output (lb-ft)258-295 tq290-330 tq

Subaru FA vs EJ: Engine Design

Both the EJ257 and FA20DIT engines are flat-four, horizontally opposed boxer style motors. This means the pistons face sideways instead of vertical or at an angle, and move side-to-side rather than up-and-down. Due to their unique construction, boxer engines offer a lower center of gravity than inline or V style engines. This helps improve straight line stability while decreasing body roll in and out of corners. Previously, we took a deep dive into the EJ257 with our engine guide, so check that out, too.

EJ257 Engine Design and Changes

Subaru designed the EJ257 engine back in the early 2000s, and have given it only minimal updates since then. The EJ257 is a 2.5L reinforced aluminum block engine, with a semi-closed deck and 8.2:1 compression ratio. It has forged rods and hypereutectic cast pistons, with a bore of 99.5mm and stroke of 79mm. The first generation also had sodium filled exhaust valves and an integrated intercooler sprayer for charge air cooling.

In 2007, Subaru added a secondary air pump for emissions, and they also had to change the cylinder heads to accommodate it, resulting in new V25 heads to replace the outgoing B25 heads. The OEM turbo also changed from an IHI VF39 to a IHI VF43, to rectify issues with wastegate cracking by stiffening it to reduce boost creep.

In 2008, Subaru again made revisions, giving the EJ257 a new turbo (IHI VF48) and new W25 heads. They also added exhaust cam timing to their Advanced Valve Control System (AVCS), which previously only utilized the intake cams. In 2009, they also introduced a nitride-treated crankshaft and slightly reinforced the connecting rods.

In 2018, Subaru finally made some real changes to the EJ257 when they put it in the limited edition WRX STi Type RA. They added reinforced pistons, new N25 heads, and increased boost for the first time on the STi, from 14.5 PSI to 16.2 PSI. In 2019, Subaru put the new version of the EJ257 into the STi, where it remained unchanged until 2021.

So basically, over an 18 year period, Subaru’s only significant adjustments were to change the heads, add exhaust cam timing, and increase boost by 1.2 PSI. As a result, power barely increased on the STi, from 300-hp in 2004 to 310-hp in 2021.

FA20DIT Engine Design

The FA20DIT is a 2.0L aluminum block engine, with 10.6:1 compression and direct injection. It has hypereutectic cast pistons and cast rods, with a forged crankshaft and open deck design. In addition, the FA20DIT longblock is also a perfectly square engine, with the same length bore and stroke.

Direct injection was the biggest change Subaru introduced in 2012 with the FA20 engine. Gasoline direct injection, or GDI or DI for short, is a new style of fueling where atomized fuel is sprayed directly into the combustion chamber. This results in more accurate fuel injection timing, which reduces emissions and creates lots of torque. It does however have some downsides, including carbon buildup, which we will get into later.

The FA20 uses a Garret GT2259 twin-scroll turbo, instead of the single-scroll turbos found on the EJ25 series of engines. The point of the twin-scroll design is to separate the exhaust gas pulses coming out of the exhaust manifold into two ports, or scrolls, which separately feed into the compressor wheel. This creates smoother flow from the exhaust into the turbo, which allows for better cam timing and more pulse energy. Combined with GDI, it means peak torque at very low RPMs, creating a much larger powerband.

Performance Differences

In its completely stock form, the EJ257 powered STi can go from zero to 60 mph in 4.8 seconds and run the ¼ mile in 13.3 seconds at 105 mph. It has a top speed of 159 mph, which is limited both electronically and by drag. Power output on the EJ257 in 2004 was 300-hp and 300-tq, and by 2021 horsepower had barely increased to 310. Due to stricter emissions, the EJ257 actually lost 10 lb-ft of torque starting in 2008, and only made 290-tq thereafter.

There is also a slightly modified version of the EJ257 in the STI S209, which Subaru limited to 209 units. This version of the EJ257 makes 341-hp and 330-tq, thanks to increased boost pressure and a larger turbo compressor wheel and turbine, as well as larger injectors and a higher flowing fuel pump and intake design.

Subaru’s FA20DIT engine had a more limited production cycle, from 2012-2021, but it still made a pretty big impact in the Subaru community. For its entire run in the USDM WRX, the FA20 made 268-hp and 258-tq.

However, for the JDM models Subaru increased power outputs to 296-hp and 295-tq. The USDM FA20 can go from zero to 60 mph in 5.1 seconds and do the ¼ mile in 13.6 seconds at 102 mph. The twin-scroll turbo and GDI system on the FA20 allow it to keep pace with the larger displacement STi.

Subaru FA vs EJ: Upgrades and Mods

Now, with much of the background info out of the way it’s time to move onto the more exciting topics. The turbo design of both the FA20DIT and EJ257 offers immense potential with some simple bolt-on mods. Upgrades are similar between the engines but there are some minor differences. Notably, the FA20 is a little more E85 friendly and has a more capable fueling system from the factory. Anyway, let’s jump in and discuss upgrades for the EJ257 vs FA20.

EJ257 Upgrades and Mods

  • ECU Tuning
  • Downpipe
  • Intake
  • Fuel Injectors (Stage 2 and above)
  • Fuel Pump (Stage 2 and above)
  • Fuel Pressure Regulator (Stage 2 and above)

While the EJ257 is a perfectly enjoyable car stock, the real fun begins when you start to modify it. Basic mods for the EJ257 are the standard intake, downpipe, and ECU tuning. Intakes will net ~5-15whp/wtq, but the OEM intake is actually pretty good, and can handle power levels up to 350-400whp without needing to be upgraded. Downpipes are by far the most popular modification for the EJ257. They add ~10-25whp/wtq by reducing exhaust flow restriction, depending on catted or catless options.

ECU tuning is the biggest bang for your buck on the EJ257, and will net 25whq/wtq by itself. Subaru engines are notoriously finicky and sensitive to air-fuel and flow changes, so any intake or exhaust modifications require tuning.

In addition, at anything “stage 2” and above, meaning anything with a downpipe and tuning, the EJ257’s fuel system is about maxed out. It is highly recommended to get larger fuel injectors, a larger fuel pump, and a fuel pressure regulator (especially for 2008 models).

The sky is truly the limit for the EJ257, and there are a ton 1000+hp builds out there with it. The aftermarket community for the STI is incredibly robust, and there are still new products being developed and released today.

FA20DIT Upgrades and Mods

  • ECU Tuning
  • J-Pipe (downpipe)
  • Intercooler
  • Intake
  • E85 Fueling

Previously, we have looked at a lot of FA20 upgrades, so we’ll just briefly go over them again and link back to our other articles for you to explore. Our guide to the top FA20 mods is a great resource that has several suggestions on mods as well as specific brands. We also have guides looking at turbo upgrades, exhaust upgrades, intake upgrades, and intercooler upgrades.

The top mod for the FA20 WRX is undoubtedly going to be ECU tuning. Just tuning alone can net 25-35whp/wtq and completely transform the powerband. Downpipes, also known as J-Pipes on the FA20 because of their shape, are another top mod. They add 10-25whp/wtq by reducing restrictions and improving the cat placement by putting it more downstream. Intakes can also add power, 5-15whp/wtq, but like on the EJ257, the OEM intake is pretty capable below 350whp.

Intercoolers are also great upgrades for those living in hotter climates or who like to do multiple pulls. The stock cooler is woefully undersized and quickly becomes ineffective after just a few consecutive runs. E85 fueling is incredible for the FA20, because the fuel lines, fuel pump, and fuel injectors are already ethanol compatible. Proper tuning is needed to safely run more than a few gallons of ethanol at a time, but the gains are off the charts.

FA vs EJ: Reliability, Common Problems, Power Limits

Previously we have already looked at the EJ257 in-depth, so again here we will just summarize our guide. We have also looked at the top 4 most common FA20 problems with our guide, too. Make sure to check both out for the full rundowns.

EJ257 Common Problems

The most common problems on the EJ257 are cracked turbos, spun bearings, rod knock, and ringland failure. The cracked turbos were mostly a product of the early VF39 wastegates, and are not an issue on 2008+ EJ25s. The succeeding years had some issues with overall turbo reliability, but for the most part they are okay.

The biggest and most notorious issues with the EJ257 are rod knock, spun bearings, and ringland failure. These issues are typically related to repeated pre-ignition and detonation events on poorly tuned engines. Detonation, or engine knock, on Subarus is typically due to lean air-fuel-ratios, too much timing advance, and high cylinder temperatures. Repeated knock events will eventually destroy connecting rods and pistons, and also lead to ringland failure.

Ringland failure is one of the most common issues for the EJ257, and it occurs when the ringlands become fractured due to excessive heat and detonation. The ringlands seal the crankcase from intruding combustion gasses, heat, and oil. When the ringlands fail, it causes major blow-by of oil into the PCV system and crankcase, leading to oil in the intercooler. If enough oil starts to leak out oil starvation problems can occur, which frequently leads to spun bearings on the EJ257.

EJ257 Power Limits and Reliability

The EJ257 block is capable of withstanding a lot of power, but the internals are not nearly as robust. The block is generally thought to be good until around 400whp before needing to be upgraded. Several aftermarket companies offer fully closed deck EJ257 blocks to withstand extra power. The pistons are the next weakest point, as the OEM hypereutectic cast pistons once again do not stand up past 375-400whp.

Anyone looking at going past 400whp on the EJ257 should really consider a built block, forged pistons, reinforced rods (OEM are already forged but not as strong as you might think), and head studs. In addition, cylinder liner sleeves are also a popular option.

Proper maintenance is key for the EJ257, and with it they have been known to easily surpass 200,000 miles in their stock form. Modifications obviously shorten the EJ257’s lifespan, but even moderate builds are capable of passing 150,000 miles with proper maintenance and responsible driving. Improper tuning and untuned modifications are the biggest threats to EJ25 longevity.

FA20DIT Common Problems

The main issues on the FA20 relate to the weak connecting rods and excessive carbon buildup. Many early WRXs saw snapped connecting rods the second they were tuned on the dyno.  While there is no definitive answer as to why that was happening, most tuners agree the issue was pushing too much torque too early in the powerband. The twin-scroll turbo and GDI fueling make for incredibly quick peak torque, but on the FA20s that was a death knell for engines pushing more power than stock.

However, tuners found that massaging out the torque hit by 300-600 RPMs, so it did not reach peak torque until past 3,300 RPMs, was the most effective way to stop premature rod failures. Most 2016+ WRXs do not suffer from rod failures as tuning has improved.

Carbon buildup is the other main issue with the GDI fueled FA20DIT. Since GDI sprays the fuel mixture directly into the combustion chamber, there is no fuel washing over the intake valves every combustion cycle. This makes them prone to carbon and soot buildup, which over time can cause serious issues with misfires, fuel economy, and performance. However, the vast majority of FA20 owners, >95%, will likely never experience carbon buildup issues. The solution for carbon buildup is to have the valves walnut blasted, but without supplemental fueling the problem will just continue to happen.

Unless you are already experiencing misfires and spark issues there is likely no need to clean your intake valves, though it certainly does not hurt. The standard interval for preventative maintenance is 40-60,000 miles, depending on power levels and driving. Excessive idling and repeated short trips where the engine is unable to get up to temperature are the biggest contributors to carbon buildup on GDI engines.

FA20DIT Power Limits & Reliability

The FA20DIT is a relatively stout engine. The block is capable of withstanding over 400whp without issues. Like the EJ257, there are also companies who offer closed deck versions of the FA20 for serious power builds. Also similar to the EJ257, the FA20’s internals are not nearly as strong as the block. The consensus is that rods and pistons are good until about 350-375whp/wtq, after which they will likely fail and need to be replaced. Anyone looking at going past 400whp should really consider a built block, forged pistons and rods, and head studs.

Since the FA20 has not been out nearly as long as the EJ25 series of engines, there is much less data on its reliability. However, early returns have shown the FA20 to be pretty solid. With proper maintenance and responsible driving, there are already plenty of 150,000+ mile examples of stock motors with no issues. Even moderately tuned FAs have shown the propensity to go well over 50-75,000 miles without issue.

There have not been nearly as many high horsepower FA20 builds as on the EJ series of engines, but there are still some notable examples. Some builds have cracked the 800whp barrier, and there are a ton of 500whp+ 2015-2021 WRXs on the road today. The GDI fueling generally needs to be supplemented for the ultra high horsepower builds, but there are some aftermarket solutions available for that.

The FA and EJ Are Two Of The Best Flat Four Engines Ever Made

Overall, both the FA20DIT and EJ257 are solid flat-four boxer engines, capable of immense power and fun. The EJ257 is one of the most iconic tuner engines of all time, and the FA20 is slowly making a name for itself in the tuning community.

Performance wise, the EJ257 is going to deliver the best power with the most aftermarket support, but the FA20 is no slouch either. Though hindered by half a liter less displacements, its GDI and twin-scroll turbo help make up for the difference. In addition, the FA20s larger torque curve also helps it scream off the line from a dig.

Which is better? There really is no true answer. For those looking at moderate power builds, who still want decent fuel economy and the newest tech, the FA20DIT is definitely the way to go. But for enthusiasts looking at squeezing the most power possible and concerned with building a true racecar, the EJ257 takes the top prize.

Do you have either a FA or EJ powered WRX or STI, or are you thinking about getting into a used one? What experience do you have tuning and modding the FA20 and EJ257?
Let us know in the comments below!

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