Closed Deck EJ25 Engine - Iconic High Performance Subaru Powerplant

Overview of the Closed Deck EJ25 Subaru Engine

The closed deck EJ25 engine produced by Subaru is one of their most popular performance engines. Used in various high-performance Subaru models over the years, most notably the Impreza WRX STI, the EJ25 is known for its power, reliability, and tuning potential.

The Closed Deck Design

What makes the EJ25 special is its closed deck design. This means the open space between the cylinders is smaller than in a standard "open deck" engine design. This allows for added strength and rigidity in the engine block itself.

The closed deck configuration also promotes better cylinder wall support, reduced cylinder bore distortion, and improved sealing for the combustion chambers. In simple terms, it allows the EJ25 to handle more power reliably.

EJ25 Engine Variants

There have been various versions of the EJ25 engine over the years, with designations like EJ255, EJ257, and EJ207 used for different engine variants:

• EJ255 - Used in the WRX STI in various markets globally
• EJ257 - Higher performance version used in the late model USDM WRX STI
• EJ207 - Version designed for the Japanese market Impreza WRX STI

While the specifications differ slightly, all feature the same stout closed deck block design for strength.

Performance & Tuning Potential

In stock form the EJ25 engine is capable of impressive horsepower figures well over 300hp, depending on the exact variant. With the closed deck block and forged internals, the engine also responds very well to performance modifications and tuning.

Common modifications include upgraded turbochargers, fuel system upgrades, higher flowing exhausts, engine management tuning, and more. This allows the FA20 engine to reliably produce over 400-500 horsepower with the right supporting modifications.

The EJ25's Place in Subaru Motorsports

The capabilities of the EJ25 closed deck engine have made it an extremely popular choice for high performance Subaru rally cars and race vehicles over the years.

The Subaru World Rally Team extensively used EJ25 powered Imprezas from the late 1990s onwards to win multiple constructor’s championships. Even today, various closed deck EJ engines power rally cars competing in events around the world.

The engine has also been used extensively in time attack and hill climb cars as well. Its combination of power and reliability works well in motorsports applications.

EJ25 Powered Rally Legends

Some of the most famous EJ25 powered rally cars include:

• Subaru Impreza WRC - Multiple championship winner from 1997-2003
• Subaru Impreza STI N14 - Famous Group N rally car campaigned by Prodrive
• Subaru WRX STI S12B - Iconic blue with gold wheels Subaru rally car

All of these legendary rally cars relied on the closed deck EJ25 engine to power them through grueling events like Rally Monte Carlo, Acropolis Rally, and more.

The Closed Deck Legacy

With its long history powering high performance Subaru road cars and race vehicles alike, the closed deck Subaru EJ25 engine has rightfully earned its status as an automotive icon.

It established Subaru’s reputation for building tough turbocharged engines and played a pivotal role in the company’s racing successes over three decades.

While newer Subaru engines like the FA20 now power the WRX STI, the EJ25 and its signature closed deck block design left behind an enduring high performance legacy that won’t soon be forgotten.

FAQs

What is a "closed deck" engine design?

A closed deck engine block has less open space between the cylinders compared to a standard "open deck" design. This allows for added strength, rigidity, and improved cylinder support in high performance applications.

Which Subaru performance models used the EJ25 engine?

The closed deck EJ25 engine powered Impreza WRX STI models globally for over 20 years, most notably the Version 5 through Version 10 STI's. It has powered some of Subaru's most iconic high performance cars.

How much power can the EJ25 reliably handle?

The EJ25 engine with the right internal upgrades and supporting modifications can reliably handle over 400-500 horsepower while maintaining driveability.

Why was the EJ25 popular in motorsports?

The EJ25 had an excellent combination of high power output, durability, and tuning potential making it a popular choice to power Subaru rally cars and race vehicles to many victories over the years.