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For over two decades, the heartthrob of the JDM world has been the Subaru EJ25 engine, a powertrain that powered countless rally victories and defined a generation of performance cars. In 2019, Subaru delivered its swan song, a final, no-holds-barred evolution of this iconic powerplant. The WRX STI Type RA S209 long block is not just an engine; it is the culmination of Subaru's entire EJ series legacy, a hand-assembled, track-forged masterpiece representing the strongest factory EJ25 ever to leave a Japanese assembly line. With an official output of 341 horsepower and 330 lb-ft of torque in the US-spec S209, this engine was built to withstand pressures and produce power levels that would make standard STI engines shudder. This deep dive explores the engineering marvel that is the S209 long block, a unit that continues to command reverence and high price tags among enthusiasts and builders years after its limited production run.
The story of the S209 cannot be told without understanding its predecessors. The "S2xx" designation belongs to Subaru Technica International (STI), the high-performance skunkworks division. These are not mere trim levels; they are limited-run, homologation-special vehicles built to showcase STI's ultimate capabilities. The lineage includes legendary models like the S201, S202, and S204, each pushing the boundaries of the contemporary Impreza platform.
The S209's direct predecessor was the WRX STI Type RA (Record Attempt), a car built to conquer time attack records. The lessons learned from the Type RA, including aerodynamic tweaks and weight reduction, were directly funneled into the S209. More importantly, the S209 was the first-ever "S" model officially exported to the United States, making its WRX STI Type RA S209 long block a holy grail for American enthusiasts who had previously only dreamed of such JDM exotica.
This engine is the final form of the EJ257 block, a code familiar to every Subaru tuner. While the standard EJ257 is a robust open-deck design suited for daily driving, it has known limitations under extreme boost and high-RPM abuse. The S209 engine addresses every single one of these weaknesses with purpose-built, upgraded components, transforming it from a potent street motor into a genuine track-ready powerhouse.
Before we dissect the upgrades, let's clarify what we're discussing. A long block assembly typically includes the engine block, cylinder heads, crankshaft, pistons, connecting rods, camshafts, and valvetrain. It is essentially a complete engine minus the "bolt-ons" like the intake manifold, fuel system, turbocharger, and ignition components. When you purchase an S209 long block for sale, you are buying this core rotating assembly, the fortified heart of the vehicle. This is the preferred solution for performance builders seeking a robust foundation, as it consolidates the most critical and expensive internal components into a single, proven package.
The magic of the WRX STI Type RA S209 long block lies in the sum of its parts. STI's engineers didn't just throw more boost at the problem; they methodically reinforced the engine's architecture from the inside out.
The single most significant upgrade is the use of a closed-deck block. Most production engines, including the standard EJ257, use an open-deck design where the cylinder walls are open at the top to the coolant passages. This is cost-effective and provides excellent cooling for street use, but it can allow cylinder walls to flex under extreme combustion pressures, a primary cause of head gasket failure and ringland issues in highly-tuned Subarus.
A closed-deck block features reinforced webbing that surrounds the upper portion of the cylinder sleeves, essentially creating a solid, monolithic structure. This design drastically increases the block's rigidity, minimizing cylinder wall flex and allowing it to reliably contain much higher cylinder pressures. This is not a new concept; it was used in Subaru's WRC cars and the legendary EJ20G "closed-deck" blocks of the 1990s. For the S209, STI brought this race-proven architecture back, making it the pinnacle of factory EJ257 upgrades for strength.
Inside this fortified block lies a fully forged rotating assembly, the key to handling high horsepower and rotational forces.
To complement the robust short-block, the S209's cylinder heads also received attention. While they share a similar basic design to other EJ25 heads, they feature a reinforced valvetrain. This includes stiffer valve springs that prevent valve float at high RPMs, ensuring precise valve control when the tachometer needle swings towards the redline. This allows the engine to breathe more effectively and safely at the upper limits of its rev range, a critical factor for track use.
While our focus is the long block assembly, its potential is fully realized through key supporting modifications made to the complete S209 car. These components work in concert with the fortified engine.
So, what does this no-expense-spared approach yield? The S209 engine specs are impressive, especially for a factory 2.5-liter boxer engine sold with a full warranty.
| Specification | Detail |
|---|---|
| Engine Code | Based on EJ257 (Enhanced) |
| Displacement | 2.5L (2457cc) |
| Block Design | Closed-deck block |
| Compression Ratio | 8.0:1 |
| Horsepower (S209 horsepower) | 341 hp @ 6,400 rpm |
| Torque | 330 lb-ft @ 3,600 rpm |
| Induction | Turbocharged and Intercooled (with water spray) |
| Key Internal Components | HKS pistons STI, Forged Connecting Rods, Nitrided Crankshaft |
| Redline | Approx. 7,000 rpm |
It's crucial to understand that these S209 horsepower and torque figures are conservative factory ratings. The engine's true potential is unlocked with specialized tuning. With supporting modifications and an aggressive tune, it's widely believed that the S209 long block is capable of supporting well over 500 wheel horsepower reliably, a testament to its overbuilt nature.
The S209 was produced in extremely limited numbers, with only 209 units coming to the United States. This scarcity, combined with its status as the ultimate expression of the EJ25, has cemented its legendary status.
For Performance Builders & Tuners, the WRX STI Type RA S209 long block represents a semi-turnkey solution for a high-horsepower build. Instead of sourcing and assembling a custom-built engine, a builder can start with this proven, factory-assembled core. It eliminates the guesswork and potential failure points of a mix-and-match component approach. Whether for a track car, a high-performance street build, or even a rally cross project, this long block assembly is a fantastic starting point.
For Potential Buyers of the complete car or its engine, the value proposition is clear. You are acquiring a piece of Subaru history, the EJ25 final edition. The engineering pedigree, the hand-assembled nature, and the documented performance gains justify the premium cost. It is an investment-grade powertrain.
Finally, the S209 marked the end of an era. It was the last hoorah for the EJ20/EJ25 engine family in a new STI before Subaru moved to the new FA24 platform. It was a fitting send-off, a car and an engine that reminded everyone of what made the STI iconic. It answered the question: "What could Subaru do if they truly unleashed the EJ25 with no compromises?" The WRX STI Type RA S209 long block is the answer.
In the US-spec S209 vehicle, the complete engine system produces 341 horsepower at 6,400 rpm and 330 lb-ft of torque at 3,600 rpm. These figures are for the fully assembled car with its specific turbo, tune, and exhaust. The long block assembly itself is capable of supporting much higher power levels with appropriate supporting mods and tuning.
The key differences are its closed-deck block for ultimate strength, forged HKS pistons, forged connecting rods, a nitrided crankshaft, and a reinforced valvetrain. It is a comprehensively fortified version of the standard EJ257 engine.
Yes, absolutely. The use of a closed-deck block is one of the most defining and critical features of the S209 long block, providing a level of cylinder wall stability unmatched by standard open-deck STI engines.
Yes, an S209 long block can be swapped into a regular WRX or older STI, but it is a complex project. It requires the engine itself, the S209's specific ECU tune, its larger turbocharger, intercooler, and equal length headers to achieve its intended performance. It also requires a skilled tuner to properly calibrate everything. It's a popular but advanced swap for those seeking the ultimate OEM+ engine upgrade.
An S209 long block for sale is a rare find and commands a premium price. A new or low-mileage used unit can cost several times more than a standard STI engine, often reaching well into five figures. They can sometimes be found through specialized JDM engine import companies, Subaru dealerships that service S209 models, or through private sales on enthusiast forums. For other high-quality Subaru engine components, you can explore our engine parts category.
The power potential is exceptional. With upgraded fuel system, turbo, and a professional tune, the S209 long block is widely regarded as capable of reliably supporting over 500 wheel horsepower. Its reliability at this level is considered superior to a standard EJ257 due to its forged internals and closed-deck block, but it still ultimately depends on the quality of the tuning and supporting components.
HKS pistons are forged aluminum pistons made by the renowned Japanese performance company HKS. They are used in the S209 because they are significantly stronger than the factory cast pistons. Forged pistons are much more resistant to detonation-induced damage (like broken ringlands), making them essential for handling the higher boost pressures and cylinder pressures needed to achieve the S209's power output and durability targets.
Based on its specification and factory intent, the WRX STI Type RA S209 long block is widely considered the strongest factory EJ25 ever produced for a road-going vehicle. Its combination of a closed-deck block and fully forged rotating assembly represents the peak of Subaru's factory engineering for this engine family.
The switch to equal length headers in the S209 was for pure performance. They create smoother exhaust pulse scavenging, which spools the turbocharger faster (reducing lag) and improves volumetric efficiency for more power, especially in the mid-range. The trade-off is the loss of the classic Subaru unequal-length header "rumble," resulting in a smoother, higher-pitched exhaust note similar to many other turbocharged performance cars.
The WRX STI Type RA S209 long block is more than just an assembly of metal parts; it is a symbol. It represents the ultimate realization of a platform that defined an era of Japanese performance. For the enthusiast, it is the answer to countless "what if" questions. For the builder, it is the most robust factory-core foundation available for a high-horsepower Subaru build. And for the collector, it is a piece of motoring history, the final, most potent word on the iconic 2.5L turbo boxer engine that powered Subaru to glory.
While the S209 car itself is a rare gem, the legacy of its engine lives on. Its design philosophy and components have set a new benchmark for what is possible, influencing a generation of aftermarket STI performance parts and build strategies. If you are considering an STI engine rebuild or a new project and have the means, starting with an S209 long block is perhaps the best decision you can make. It is the definitive EJ25 final edition, a masterpiece of engineering that marks the end of a legendary chapter in automotive history.
For all your Subaru performance and OEM replacement part needs, from clutch kits like the ACT Xtreme Duty Clutch to cooling upgrades like our Alpha Series Aluminum Radiator, explore our full catalog at Genuine Subie Parts.
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