Subaru’s FA20DIT and EJ257 performance engines are among the brand’s best-selling powertrains ever. One of the most famous and storied tuner engines ever is the EJ257. From 2004 on, it was used to power the STi in North America, where it was consistently one of the best performing alternatives available. The FA20 debuted in 2012 and was first installed in the Subaru WRX in 2015, where it quickly earned acclaim for its exceptional performance and wide range of customization options.
In 2021, Subaru officially stated that production of both of its boxer engines would cease. In North America, the EJ series has been phased out, while the FA20 carries on in the form of the larger-displacement FA24. It’s a shame, considering both of these motors are top-notch. Both came factory equipped with more than enough horsepower, and they continue to enjoy massive aftermarket support. Both engines have some serious flaws, but they’re still serviceable in most cases.
Which is better, the FA20 or the EJ257? has become a common question among aficionados in recent years. We’ll take a look at the design, dependability, and—most importantly—performance and upgrades of both engines, so you won’t have to worry about missing a thing. What are we waiting for?
Subaru 2.5 L EJ History
Subaru debuted their EJ series of motors in the late ’80s, taking the place of their venerable EA motors. Initially debuted in 1996, the EJ25 was followed by the STi-tuned EJ257 in 2004. The EJ257’s output of 300 horsepower and 300 lb-ft of torque in 2004 was incredible for an engine used in a budget car at the time. In comparison to the 4G63 in the Mitsubishi Evo, it produced greater power and was much praised by both amateur and professional racecar drivers.
Within a few years, completely built variants of the EJ257 appeared on the market, featuring fully closed deck designs and forged internals, allowing for extremely high horsepower builds. There are innumerable cool and unusual builds that make use of the EJ257, which has made it a perennial favorite among tuner enthusiasts. In 2022, many professional racing teams are still praising the EJ257 for all its supposedly miraculous abilities.
Subaru 2.0 L DIT History
In 2012, Subaru began releasing the FA20DIT, although only in Japan at first. Subaru initially introduced it to the United States market with the Forester XT in 2014, and then to the WRX the following year. Originally, the FA20DIT in the WRX produced 268 horsepower and 258 pound-feet of torque, but for the Japanese Domestic Market (JDM), Subaru increased those figures to 296 horsepower and 295 pound-feet of torque. Although the FA20’s initial image was tarnished because of its smaller displacement than the outgoing WRX engine, the EJ255, the FA20 quickly won over skeptics.
Aftermarket enthusiasts quickly took to the FA20, and soon there were a plethora of customization options available. Though the engine’s internals weren’t as sturdy as its competitor, the EJ257, producing moderate power was more simpler. The car is E85 compatible out of the box, albeit it needs calibration for safe use, thanks to the newly developed direct injection system.
After 2021, production of both engines was halted. Both the FA20 and the EJ257 were discontinued because their successors, the WRX, became available and because the EJ257’s antiquated architecture caused too many emissions problems for Subaru. Even yet, automobiles powered by the FA20DIT and EJ257 can still be found everywhere, and their engines have a long future ahead of them thanks to a thriving aftermarket. At least until the advent of the electric vehicle revolution catches up with them.
FA20DIT & EJ257: Specs
Specs for the Subaru FA20 vs EJ257 engines are as follows:
|Years in production||2012-2021||2004-2021|
|Configuration||Flat 4 (Boxer)||Flat 4 (Boxer)|
|Valve Train||16V DOHC||16V DOHC|
|Turbo Design||Twin-scroll Turbo||Single-scroll Turbo|
|Displacement||2.0 L (1,998 cc)||2.5 L (2,457 cc)|
|Fuel System||Direct Injection||Fuel Injection|
|Bore & Stroke||86mm x 86mm||99.5mm x 79mm|
|Boost Pressure||15.9 PSI||14.5 PSI|
|Horsepower Output||250-296 hp||300-341 hp|
|Torque Output (lb-ft)||258-295 tq||290-330 tq|
FA20DIT & EJ257: Applications
2012-2014 Subaru Legacy 2.0GT DIT (JDM only)
2014+ Subaru Levorg (JDM & ADM only)
2014-2018 Subaru Forester XT
2015-2021 Subaru WRX
2015+ Subaru WRX S4 (JDM only)
2004-2014 Subaru Impreza WRX STi
2015-2021 Subaru WRX STi
2004-2005 Subaru Forester XT
2005-2006 Subaru Legacy 2.5 GT
2005-2006 Subaru Outback 2.5XT
Subaru FA vs EJ: Engine Design
The EJ257 and FA20DIT are similarly equipped with flat-four, horizontally opposed boxer motors. That the pistons are oriented laterally rather than vertically or at an angle, and that they travel laterally rather than vertically. Boxer engines have a lower center of gravity than inline or V-shaped engines because of their design. This helps increase stability when traveling in a straight line and reduces body roll when accelerating out of a bend. You should also check out our engine guide, in which we delved even further into the EJ257.
EJ257 Engine Design and Changes
The Subaru EJ257 engine was originally developed in the early 2000s, and has had relatively minor revisions since then. The EJ257 is a 2.5-liter aluminum-block engine with a semi-closed deck and 8.2:1 compression ratio. The rods are forged, and the pistons are hypereutectic cast; the bore is 99.5mm and the stroke is 79mm. In addition to the charge air conditioning intercooler sprayer, the first generation also had sodium-filled exhaust valves.
With the addition of the secondary air pump for emissions in 2007, Subaru also had to modify the cylinder heads, resulting in the new V25 heads that replaced the older B25 heads. After experiencing wastegate cracking, the OEM turbo was upgraded to a more robust IHI VF43, which effectively eliminated boost creep.
Again in 2008, Subaru updated the EJ257 with a new turbo (the IHI VF48) and updated W25 cylinder heads. The Advanced Valve Control System (AVCS) wasn’t complete until the exhaust cam timing was incorporated. As of 2009, they also began using a nitride-treated crankshaft and had the connecting rods modified slightly for added strength.
In 2018, Subaru introduced the WRX STi Type RA, a special edition car that included a modified version of the EJ257. For the first time, the STi’s boost pressure was raised from 14.5 PSI to 16.2 PSI, and new N25 cylinder heads were installed. Starting in 2019, Subaru has installed the updated EJ257 into the STi, and it will remain there until 2021.
In other words, over the course of 18 years, Subaru made only three major modifications: a head swap, exhaust cam timing addition, and a 1.2 psi boost increase. As a result, the STi’s output grew only slightly from 300 horsepower in 2004 to 310 horsepower in 2021.
FA20DIT Engine Design
Direct injection and a compression ratio of 10.6:1 are featured in the FA20DIT engine, which has a 2.0-liter aluminum block. Cast hypereutectic pistons and rods, forged crankshaft, and an open deck layout are some of its notable features. The FA20DIT longblock is also a precisely square engine, having a bore and stroke of the same length.
In 2012, Subaru debuted the FA20 engine, which had a number of upgrades, the most notable of which was direct injection. The gasoline direct injection (GDI or DI) system is a relatively recent method of fueling that involves spraying fuel atomizers into the engine’s combustion chamber. More precise fuel injection timing leads to less pollution and more torque. We shall discuss the drawbacks, such as carbon accumulation, in more detail below.
If you’re familiar with the EJ25 series of engines, you’ll see that the FA20 has a Garret GT2259 twin-scroll turbo instead of the single-scroll turbos. The twin-scroll design is intended to divide the exhaust gas pulses leaving the exhaust manifold into two streams that are then fed into the compressor wheel in a sequential fashion. This improves cam timing and pulse energy by smoothing out the exhaust flow into the turbo. When coupled with GDI, this provides maximum torque at relatively low RPM, which results in a wider powerband.
Subaru FA20 vs EJ257: Performance
The stock STi with the EJ257 engine can accelerate to 60 miles per hour in 4.8 seconds and complete the quarter mile in 13.3 seconds at 105 miles per hour. Electronic and aerodynamic resistance limit its maximum speed to 159 mph. In 2004, the EJ257 produced 300 hp and 300 lb-ft of torque; by 2021, that number had risen little to 310. After 2008, the EJ257 was only able to produce 290-tq because of increased emission regulations.
Subaru also produced a limited run of 209 STI S209s with a slightly revised EJ257 engine. With greater boost pressure, a larger turbo compressor wheel and turbine, larger injectors, a higher flowing fuel pump, and an improved intake design, this EJ257 produces 341 horsepower and 330 pound-feet of torque.
The FA20DIT engine for Subaru vehicles was only manufactured from 2012 to 2021, yet it had a significant impact on the Subaru fan base. In its entirety, the FA20 produced 268 horsepower and 258 pound-feet of torque in the USDM WRX.
For the Japanese domestic market versions, however, Subaru bumped those numbers up to 296 hp and 295 lb-ft of torque. The US Military FA20 can go from 0-60 mph in 5.1 seconds and complete the 1/4 mile in 13.6 seconds at 102 mph. The FA20 can compete with the bigger displacement STi because to its twin-scroll turbo and GDI technology.
Subaru FA vs EJ: Upgrades and mods
With that preamble out of the way, we can dive into the meatier discussions at hand. Simple bolt-on modifications to either the FA20DIT or EJ257 turbo design unlock enormous potential. Both engines benefit similarly from upgrades, albeit there are some subtle distinctions between them. One key difference is that the FA20 comes with a factory-installed fueling system that is more competent and slightly more E85-friendly. Anyway, let’s dive in and compare the EJ257 and FA20 in terms of their newest features.
EJ257 Upgrades and Mods
Best EJ257 Mods:
- ECU Tuning
- Fuel Injectors (Stage 2 and above)
- Fuel Pump (Stage 2 and above)
- Fuel Pressure Regulator (Stage 2 and above)
The EJ257 is a fun car as-is, but the true excitement lies in the possibilities for customization. The basic intake, downpipe, and ECU tuning are the foundation of every EJ257 modification. Power gains from intakes typically range from 5 to 15 hp and the factory intake is adequate for engines producing 350 to 400 horsepower without modification. By far, the most common upgrade for the EJ257 is a set of downpipes. They increase power by 10–25 hp/tq, depending on whether the exhaust is catted or catless.
By itself, ECU tweaking for the EJ257 may add 25 hp and 25 lb-ft of torque. Intake and exhaust adjustments necessitate tuning for Subaru engines because of their sensitivity to air-fuel and flow alterations.
Furthermore, the EJ257’s fuel system is pretty well at its limit at “stage 2” and higher, which is to say anything with a downpipe and tuning. Increasing the size of your fuel injectors, fuel pump, and fuel pressure regulator is a must (especially for 2008 models).
The EJ257’s potential is practically limitless, and many cars with 1000+ horsepower have been built around it. The STI has a thriving aftermarket with new products regularly being introduced.
FA20DIT Upgrades and Mods
Best FA20DIT Mods:
- ECU Tuning
- J-Pipe (downpipe)
- E85 Fueling
Because we have already covered a lot of ground in previous articles, we will only briefly go over the FA20 enhancements we have already covered and provide links to those articles. Read on for some of our favorite picks for FA20 mods, including specific brand recommendations. Turbochargers, exhaust systems, air intake systems, and intercoolers are all covered in detail in our guides.
ECU tuning is going to be the most popular upgrade for the FA20 WRX. As much as 25–35 additional horsepower and torque can be gained with tuning alone, which would entirely alter the powerband. The FA20 also benefits from downpipes, or J-Pipes as they are colloquially known. Removing or lowering constraints and repositioning the cat further downstream adds 10–25 whp/wtq. Power can be gained with intake upgrades (5-15whp/wtq), although the factory intake on the EJ257 is sufficient for outputs under 350 hp.
If you live in a hotter climate or enjoy pulling numerous times, an intercooler is a worthwhile investment. After only a few uses, the default cooler becomes useless due to its inadequate size. The FA20’s fuel lines, fuel pump, and fuel injectors are all designed to work with ethanol, thus it can be fueled with E85 with no problems. Tuning is required to run more than a few gallons of ethanol at a time, but the gains are through the roof.
FA vs EJ: Reliability, Common Problems, Power Limits
Since we have already examined the EJ257 in detail elsewhere, we will once again merely provide a brief overview here. Additionally, our article also covers the top four most frequent FA20 issues. To get the entire scoop, read both.
EJ257 Common Problems
Chipped turbos, spun bearings, rod knock, and ringland failure are the most typical issues with the EJ257. The EJ25s manufactured in 2008 and after do not suffer from the broken turbos that plagued earlier models of the vehicle. In the years that followed, there were a few problems with turbo dependability, but generally speaking, everything were well.
Rod knock, spun bearings, and ringland failure are the most serious and widely publicized problems with the EJ257. Repeated pre-ignition and detonation events on poorly tuned engines are a common cause of these problems. Subarus frequently experience detonation, also known as engine knock, as a result of lean air-fuel-ratios, excessive timing advance, and hot cylinders. In the long run, repeated knocking will cause ringland failure and the destruction of connecting rods and pistons.
EJ257 ringland failure occurs when the ringlands crack as a result of extreme heat and detonation, and is one of the most common problems. Crankcase gaskets, or ringlands, prevent combustion gases, heat, and oil from entering the crankshaft. Major blow-by of oil into the PCV system and crankcase, which eventually leads to oil in the intercooler, is caused when the ringlands fail. Oil starvation issues commonly cause spinning bearings on the EJ257 if enough oil begins to leak out.
EJ257 Power Limits and Reliability
The EJ257 block can take a beating, but its guts aren’t as sturdy as the outside. Many people believe that the block can handle power up to 400 whp before it needs to be improved. Completely closed deck EJ257 blocks are available from a number of aftermarket suppliers, allowing them to resist significant increases in output. The pistons are the next most vulnerable component, as the OEM hypereutectic cast pistons again fail at power levels above 375-400whp.
The EJ257 needs a constructed block, forged pistons, reinforced rods (OEM are already forged but not as robust as you may believe), and head studs if you want to get more than 400 hp. Furthermore, cylinder liner sleeves are also a common choice.
The EJ257 may easily go over 200,000 miles if properly cared for, and even longer if modified. Although the EJ257’s lifespan is certainly shortened by modifications, even moderate builds can go far beyond 150,000 miles with regular maintenance and cautious driving. The biggest dangers to EJ25 lifetime are improper tuning and untuned alterations.
FA20DIT Common Problems
Weak connecting rods and excessive carbon buildup are the primary problems of the FA20. Connecting rods in several early WRXs broke the moment the cars were tuned on the dyno. While the exact cause is unknown, most tuners agree that the issue was the application of excessive torque at too low of an engine speed. High peak torque is produced instantly by the twin-scroll turbo and GDI fueling, but in the FA20s, this was the kiss of death for engines producing more than standard output.
Tuners, however, discovered that delaying the peak torque until RPMs higher than 3,300 was the most effective strategy to prevent premature rod failures. Tuning improvements have eliminated rod failures in most 2016 and newer WRX models.
The FA20DIT’s carbon accumulation is an additional major problem outside the GDI itself. No fuel is wasted due to washing over the intake valves during combustion cycles since GDI sprays the fuel mixture straight into the combustion chamber. As a result, carbon and soot tend to accumulate in them, which can lead to misfires, poor fuel efficiency, and poor performance over time. Most FA20 owners, perhaps as many as 95%, will never have to worry about carbon accumulation. The carbon buildup issue can be fixed by having the valves walnut blasted, but without more fueling, the issue will persist.
Cleaning the intake valves is not strictly necessary unless you are suffering misfires or spark problems. Preventative maintenance is often performed every 40-60,000 miles, depending on the vehicle’s power output and the driver’s habits. Carbon buildup on GDI engines is mostly caused by excessive idling and repeated short journeys during which the engine is unable to get up to temperature.
FA20DIT Power Limits & Reliability
When compared to other engines, the FA20DIT is quite sturdy. More than 400 horsepower can be safely applied to the block without any problems. Companies also provide closed-deck variants of the FA20 for high-output builds, much like the EJ257. The FA20’s internals are just as weak as the block, just as the EJ257’s. It is generally agreed that connecting rods and pistons can handle up to roughly 350-375whp/wtq before they start to wear out and need to be replaced. Anyone planning on making more above 400 hp should seriously consider upgrading to a constructed block, forged pistons and rods, and head studs.
There is significantly less information on the FA20’s reliability than there is on the EJ25 family of engines because it has not been on the market nearly as long. However, first data shows that the FA20 is reliable. There are several examples of stock motors that have been driven responsibly for 150,000 miles or more without any problems. FAs with average tuning have proven capable of cruising for well over 50,000 kilometers without breaking down.
Although there have not been as many high-horsepower FA20 builds as there have been with the EJ series of engines, there have been a few standouts. There are numerous 2015-2021 WRXs on the road today with 500 hp or more, and some builds have even broken the 800 hp mark. In most cases, ultra high horsepower setups will necessitate supplementary GDI fueling, however there are aftermarket options for this.
FA20DIT vs EJ257: Summary
Both the FA20DIT and the EJ257 are excellent flat-four boxer engines that can produce a lot of torque and provide a thrilling driving experience. It’s no secret that the EJ257 is a legendary tuner engine, and it’s also no secret that the FA20 is quickly becoming a household name among enthusiasts.
The EJ257 will provide the most power and the widest range of aftermarket accessories, but the FA20 won’t be far behind. The GDI and twin-scroll turbo assist in making up for the half-liter displacement loss. The FA20 has a wider torque curve, which contributes to its lightning-fast acceleration from a stop.
Which one is superior? Truthfully, there is no correct response. The FA20DIT is an excellent option for individuals who are interested in moderate power builds but still value good gas mileage and cutting-edge features. To get the most out of your engine and construct a genuine racecar, though, the EJ257 is your best bet.