The Subaru Impreza WRX STI 2.5, produced from 2005 to 2007, represents a significant evolution of the iconic rally-bred Impreza. This facelift of the second-generation Impreza (GD chassis) brought increased power and refined handling, solidifying the STI’s reputation as a formidable performance car. Positioned as the top-tier performance variant of the Impreza lineup, it sat above the naturally aspirated Impreza and the turbocharged WRX, offering a more focused and aggressive driving experience. The 2005-2007 STI was a key model for Subaru in the US market, appealing to enthusiasts seeking a capable all-wheel-drive performance sedan.
Technical Specifications
| Brand | Subaru |
| Model | Impreza |
| Generation | Impreza II (facelift 2005) |
| Type | WRX STI 2.5 (280 Hp) AWD |
| Start of production | 2005 |
| End of production | 2007 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 15.3 l/100 km (18.5 UK mpg, 6.5 km/l) |
| Fuel consumption (extra urban) | 8.3 l/100 km (28.3 US mpg, 34 UK mpg, 12 km/l) |
| Fuel consumption (combined) | 10.9 l/100 km (21.6 US mpg, 25.9 UK mpg, 9.2 km/l) |
| CO2 emissions | 257 g/km |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 5.4 sec |
| Acceleration 0 – 62 mph | 5.4 sec |
| Acceleration 0 – 60 mph | 5.1 sec |
| Maximum speed | 255 km/h (158.45 mph) |
| Emission standard | Euro 4 |
| Weight-to-power ratio | 5.3 kg/Hp |
| Weight-to-torque ratio | 3.8 kg/Nm |
| Power | 280 Hp @ 5600 rpm |
| Torque | 392 Nm @ 4000 rpm (289.12 lb.-ft. @ 4000 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | EJ257 |
| Engine displacement | 2457 cm3 (149.94 cu. in.) |
| Number of cylinders | 4 |
| Engine configuration | Boxer |
| Cylinder Bore | 99.5 mm (3.92 in.) |
| Piston Stroke | 79 mm (3.11 in.) |
| Compression ratio | 8.2:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | DOHC |
| Engine oil capacity | 4.3 l (4.54 US qt | 3.78 UK qt) |
| Coolant capacity | 7.7 l (8.14 US qt | 6.78 UK qt) |
| Kerb Weight | 1495 kg (3295.91 lbs.) |
| Max. weight | 1900 kg (4188.78 lbs.) |
| Max load | 405 kg (892.87 lbs.) |
| Trunk (boot) space | 401 l (14.16 cu. ft.) |
| Fuel tank capacity | 60 l (15.85 US gal | 13.2 UK gal) |
| Max. roof load | 80 kg (176.37 lbs.) |
| Permitted trailer load (braked) | 1200 kg (2645.55 lbs.) |
| Permitted trailer load (unbraked) | 500 kg (1102.31 lbs.) |
| Length | 4465 mm (175.79 in.) |
| Width | 1740 mm (68.5 in.) |
| Height | 1440 mm (56.69 in.) |
| Wheelbase | 2525 mm (99.41 in.) |
| Front track | 1490 mm (58.66 in.) |
| Rear track | 1495 mm (58.86 in.) |
| Ride height | 155 mm (6.1 in.) |
| Turning circle | 12.4 m (40.68 ft.) |
| Drivetrain | All wheel drive (4×4) |
| Gearbox | 6 gears, manual transmission |
| Front suspension | Spring Strut, Transverse stabilizer |
| Rear suspension | Spring Strut, Transverse stabilizer |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Hydraulic |
| Tires size | 225/45 R17 |
| Wheel rims size | 8J x 17 |
INTRODUCTION
The 2005-2007 Subaru Impreza WRX STI 2.5 marked a significant shift for the model. The “facelift” brought revised styling, including a new front bumper, headlights, and taillights. More importantly, it featured a larger 2.5-liter engine, replacing the previous 2.0-liter unit. This engine upgrade was crucial, not only for increasing power but also for improving low-end torque, addressing a common criticism of the earlier STI models. Built on the 1HX0/A3 platform, the STI continued to offer a compelling blend of practicality and performance, appealing to a broad range of driving enthusiasts.
Powertrain & Engine Architecture
The heart of the 2005-2007 STI is the EJ257 2.5-liter turbocharged boxer engine. This engine, a hallmark of Subaru’s engineering, features a closed-deck block for increased strength, a larger turbocharger, and revised internals compared to the earlier 2.0-liter EJ207. The EJ257 utilizes multi-point fuel injection and a dual overhead camshaft (DOHC) valvetrain with four valves per cylinder. The turbocharger is an IHI VF36, providing boost pressure optimized for both performance and reliability. The engine’s longitudinal mounting and all-wheel-drive system contribute to its balanced handling characteristics. The STI exclusively came with a six-speed manual transmission, known for its robust construction and precise shifts. This transmission was specifically designed to handle the increased power and torque output of the 2.5-liter engine.
Driving Characteristics
The 2005-2007 STI delivers a thrilling driving experience. The 280 horsepower and 289 lb-ft of torque provide strong acceleration, with a 0-60 mph time of around 5.1 seconds. The six-speed manual transmission allows for precise control and keeps the engine in its optimal power band. Compared to the WRX, the STI offers significantly more power and a more responsive throttle. The STI’s suspension is tuned for performance, providing a firm but controlled ride. The all-wheel-drive system provides exceptional grip, particularly in adverse weather conditions. While the ride is firmer than the standard Impreza, it’s not overly harsh, making it suitable for daily driving. The steering is precise and communicative, providing excellent feedback to the driver.
Equipment & Trim Levels
The STI came well-equipped, even by today’s standards. Standard features included sport seats with bolstering, a leather-wrapped steering wheel, air conditioning, power windows and locks, and a premium audio system. The interior featured unique STI badging and aluminum pedal covers. Optional extras included a sunroof, leather upholstery, and a navigation system. The STI’s interior was focused on functionality and driver engagement, rather than outright luxury. The dashboard layout was straightforward and easy to use, with all essential controls within easy reach.
Chassis & Braking
The STI’s chassis was specifically engineered to handle the increased power and performance. It features reinforced suspension components, including thicker stabilizer bars and stiffer springs. The front suspension utilizes MacPherson struts, while the rear features a multi-link setup. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power. The STI also features an Anti-lock Braking System (ABS) as standard equipment. The chassis design prioritizes handling and stability, providing a confident and predictable driving experience.
Market Reception & Comparison
The 2005-2007 Subaru Impreza WRX STI 2.5 was widely praised by automotive critics for its performance, handling, and all-weather capability. However, its fuel economy (around 21.6 mpg combined) was often cited as a drawback. Compared to the WRX, the STI offered a significant performance upgrade, but at a higher price point. The STI also required more frequent maintenance due to its higher-performance engine and drivetrain. Against competitors like the Mitsubishi Lancer Evolution, the STI was often considered to be more user-friendly and practical, while the Evolution offered a more raw and focused driving experience.
Legacy
The 2005-2007 Subaru Impreza WRX STI 2.5 remains a highly sought-after performance car in the used market. The EJ257 engine, while known for its potential, can require diligent maintenance, particularly regarding oil changes and cooling system upkeep. Well-maintained examples command a premium price. The STI’s robust construction and all-wheel-drive system contribute to its long-term reliability. It continues to be a popular choice for enthusiasts who appreciate its blend of performance, practicality, and rally-bred heritage. The 2005-2007 STI is considered a pivotal model in the Impreza lineage, representing a significant step forward in terms of performance and refinement.
