Segment:
Performance Compact Sedan/Wagon
Key Differentiator:
All-wheel-drive, turbocharged boxer engine, rally heritage
Competitors:
Mitsubishi Lancer Evolution, Mitsubishi Eclipse GT, Ford Focus SVT, Volkswagen GTI
Engine Layout:
Horizontally Opposed (Boxer)
Drivetrain:
Symmetrical All-Wheel Drive (SAWD)
Performance Focus:
Designed for spirited driving and performance handling, often favored by enthusiasts and in motorsports.
Powertrain:
Engine, transmission, drivetrain, fuel system, exhaust system
Chassis:
Suspension (front and rear), steering, brakes (including ABS), wheels, tires
Electrical:
Wiring diagrams, lighting, battery, charging system, ignition system, starter, ECU, sensors, body electronics
Body:
Body panels, interior trim, exterior trim, glass, doors, seats, HVAC system
Diagnostics:
Troubleshooting guides, fault codes (OBD-II), diagnostic procedures
Maintenance:
Scheduled maintenance, fluid changes, filter replacements, inspections
Repair:
Engine overhaul, transmission repair, brake system repair, suspension component replacement, electrical system troubleshooting and repair
Diagnostics:
Step-by-step diagnostic procedures for common and complex issues
Specifications:
Torque specifications, tolerances, clearances, diagnostic values
Depth:
Comprehensive, covering everything from routine maintenance to complete engine and transmission rebuilds, including electrical schematics and diagnostic procedures.
Engine Type:
2.5L DOHC 16-valve turbocharged flat-four boxer engine
Horsepower:
265 hp @ 6000 rpm (approx.)
Torque:
251 lb-ft @ 3600 rpm (approx.)
Bore X Stroke:
99.5 mm x 79.0 mm
Fuel Delivery:
Sequential Multi-Port Fuel Injection (MPI)
Turbocharger:
Mitsubishi TD05H-16G or similar (specifics may vary slightly by market/year, but this is a common OEM fitment)
Intercooler:
Top-mounted air-to-air intercooler
Ignition System:
Electronic ignition with coil-on-plug technology
Transmission Type:
6-speed manual transmission
Optional Transmission:
N/A (Manual transmission was standard for WRX STi in this generation)
Dccd:
Driver Controlled Centre Differential (DCCD) for adjustable torque split between front and rear axles.
Differentials:
Front Helical Limited Slip Differential (LSD), Rear Viscous Coupling Limited Slip Differential (VLSD) or Active Torque Split AWD system depending on specific model variant and market. The manual will detail servicing of these.
Wheelbase:
2,510 mm (98.8 inches)
Length:
4,405 mm (173.4 inches)
Width:
1,740 mm (68.5 inches)
Height:
1,425 mm (56.1 inches)
Curb Weight:
Approximately 1,450 kg (3,197 lbs)
Gross Weight Rating:
Not explicitly stated, but typically around 1,900 kg (4,189 lbs)
Trunk Volume:
Approximately 11.3 cubic feet (sedan) / 30.7 cubic feet (wagon with rear seats up)
NHTSA Front Impact:
4-star driver, 5-star passenger (for 2004 model year)
IIHS Frontal Offset:
Good (for 2004 model year)
ABS:
Standard Anti-lock Braking System (ABS)
Traction Control:
Standard Traction Control System (TCS)
Airbags:
Front dual-stage airbags, front side-impact airbags
Seat Belts:
Pretensioner front seat belts with load limiters
Body Structure:
Reinforced Zone construction, front and rear crumple zones
Audio System:
Factory AM/FM/CD player with optional premium sound system (e.g., Clarion or McIntosh).
Navigation:
Optional factory satellite navigation system (less common for this era).
Cruise Control:
Standard electronic cruise control.
Climate Control:
Manual or automatic climate control depending on trim level.
Auxiliary Input:
Rarely standard, but some models might have an aftermarket or dealer-installed auxiliary input for audio devices.
Oil Change:
Every 3,750 miles or 6 months, whichever comes first (for severe driving conditions common to performance cars).
Air Filter Replacement:
Every 15,000 miles or 12 months.
Spark Plug Replacement:
Every 30,000 miles (iridium plugs recommended).
Timing Belt Replacement:
Every 105,000 miles or 7 years (if applicable - check if this specific engine variant uses a belt or chain, but typically EJ257 uses a belt). The manual will confirm.
Engine Oil:
API SG or SH certified, SAE 5W-30 viscosity recommended. Synthetic oil highly recommended for performance use.
Coolant:
Subaru Super Coolant (blue type) or equivalent P-HOAT coolant. Capacity approx. 7.4 quarts.
Brake Fluid:
DOT 3 or DOT 4 brake fluid.
Transmission Fluid:
For 6MT: Hypoid gear oil SAE 75W-90 GL-5. Capacity approx. 2.4 quarts.
Differential Fluid Front:
Hypoid gear oil SAE 75W-90 GL-5. Capacity approx. 0.8 quarts.
Differential Fluid Rear:
Hypoid gear oil SAE 75W-90 GL-5. Capacity approx. 1.0 quart.
Head Gaskets:
While EJ257s are generally more robust than earlier EJ series, head gasket issues can still occur due to high cylinder pressures. The manual will detail proper torque procedures for reassembly.
Piston Ringland Failure:
Can occur with aggressive tuning or detonation. Proper fueling and detonation control are critical. Manual provides specifications for piston ring checks.
Clutch Wear:
High-performance clutch can wear faster under aggressive driving. Manual provides clutch inspection and replacement procedures.
Rally Roots:
Subaru has a strong motorsport heritage, particularly in the World Rally Championship (WRC), which heavily influenced the development of the WRX and WRX STi models.
Gd Generation:
The 2004 model falls into the second generation (GD/GG) of the Impreza, specifically the early 'bug eye' to 'hawk eye' transition period (this 2004 model is considered the start of the latter styling evolution, sometimes referred to as 'blob eye' or early 'hawk eye').
Sti Enhancements:
The 'STi' designation signifies a higher-performance variant with specific engine tuning, suspension upgrades, drivetrain enhancements, and often unique body styling compared to the standard WRX.
Manufacturing Location:
Japan (Gunma Plant)
Car And Driver 10Best:
The Subaru Impreza WRX (and by extension, the STi) was frequently lauded by automotive publications for its performance and value, often appearing on 'best of' lists, though specific STi wins for 2004 might be less documented than the standard WRX.
Performance Reviews:
Consistently praised for its handling, grip, and accessible performance for its price point.
