FAST

FACTS

The Subaru Tecnica International (STI) division was created in the late ’80s to help develop race cars for the FIA World Rally Championship. Subaru immediately made a name for itself in rallying, and the company decided to inject some of the STi technology into its street cars to capitalize on their success. Subaru’s highest performing street car, the WRX STi, features a sophisticated suspension derived from Subaru’s FIA World Rally Championship race cars
The STi’s body kit was designed by none other than Peter Stevens, who is most famous for designing the McLaren F1 supercar. All aero pieces (not just the rear wing) are effective at creating downforce
The large air scoop forces air through an intercooler, which feeds an IHI turbo pushing 14.5 lbs of boost. The system includes a driver-activated water mist system that can spray water onto the intercooler at the push of a button, reducing charge-air temperatures
The STi is much more than just a WRX with a bigger engine. The chassis is stiffened with additional crossmembers front and rear, and the unique forged aluminum BBS wheels house Brembo brakes front and rear. Even the Bridgestone Potenza tires were engineered specifically for the STi. Shocks, bushings, and sway bars are all upgraded over the stock WRX
STI models receive their own close ratio 6spd manual. Lesser models use a 5spd. STI’s can’t be optioned with an automatic transmission
The most unique feature about the STI’s AWD system is the ability for the driver to control the amount of “lock” based on available traction (for different terrains) via the driver-selectable modes inside the car (DCCD). The AWD system itself uses a planetary gear-type center differential that works harmoniously with an electronically controlled multi-plate clutch and a mechanical limited-slip differential to vary torque between the front and rear wheels. By default, power is split 35% front and 65% rear. Sensors monitor wheel slippage, steering angle, throttle position, and braking to help determine torque distribution and direct it to the wheels with the most traction
Subaru’s EJ engine has been around for nearly two decades (and counting). These engines are famous for their distinctive exhaust rumble, which can be attributed to the EJ25’s unequal exhaust runner length. The exhaust gasses from two of the cylinders have to travel farther than the other two, leading to an unequal spacing between the exhaust pulses. The uneven pulse spacing gives the EJ an offbeat exhaust burble. The unusual firing order (1-3-2-4) also plays a role in the exhaust noise

Key Model Year Changes:

2004
2004 was the first year of the STI, and was unique in many aspects. Easily distinguished by their clear (non-smoked) headlights and one-year only interior Nicknamed the "blob eye" due to the design of the headlights '04 and '05 models have the most RWD biased AWD systems (35/65 torque split, vs 41/59 on later cars) 2004 STi's were not equipped with any stereo or speakers. This was done as a weight-saving measure by Subaru. While a sound system was available as an option, it wasn't cheap ($1000) and it was rarely ordered
2005
Updated interior (The badging, steering wheel, shift knob, HVAC controls, and center console are updated) First year of the 5x114.3 bolt pattern (previous year used a 5x100 bolt pattern) First year of the larger rear fender flares to accommodate larger 8" wide wheels (vs 7.5") wheel size. The increased wheel width reduced steering wheel lock-to-lock The forward lateral links in the rear suspension are now aluminum New stronger wheel hubs are employed Axles are thicker First year of the helical front LSD, replacing the Suretrac unit First year of the yaw sensor (DCCD system, "Driver Controlled Center Differential") First year of the immobilizer. A stereo is now standard equipment
2006
Only year of the roof spoiler First year of the updated tail lights, daytime running lights, and lower profile hood scoop DCCD receives a mechanical limited slip mechanism to supplement the electromagnetic DCCD, and the torque split is changed to 41/59 The DCCD now has a steering wheel sensor to improve response in cornering The engine mounts switch from metal to hydraulic fluid filled plastic mounts to reduce vibration. However, durability issues force Subaru to revert back to the old metal/rubber mounts later in the year The "i" in STI is now capitalized in US marketing material
2007
First year of the Limited model (a softened STI with no wing) control arms are downgraded to cut costs (still aluminum, but no longer the Japanese Spec C control arms) Caster angle is reduced, shortening the wheelbase from 100" to 99.4" Rear sway bar is decreased from 20 mm to 19 mm The gear ratios of 2nd, 3rd and 4th gears are now taller in order to boost fuel economy. This unintentionally reduced 1/4 times, as a shift to 5th gear is no longer required before crossing the trap While the cylinder heads are redesigned to improve cooling, the sodium-filled exhaust valves are dropped Alternator is upgraded to 110 amps (vs 90 amps) The rear LSD is now a Torsen type (vs the old clutch type) The turbo is now a VF43, which uses a different wastegate actuator compared to the previous VF39 Side cowl bracing is now stiffer An audio jack replaces the ashtray Rear seat now includes a center armrest with trunk pass-through Audio system is now 120 watt ECU is updated to meet US LEV2 emissions requirements, which required a secondary air pump Fuel injectors are now a "top feed" style (replacing the old "side feed" style)