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news :: subaru
All-New Platform with Competition-Inspired 5-Door Body
305-HP Intercooled / Turbocharged Boxer Engine
New Multi-Mode DCCD All-Wheel Drive System and VDC
New Double-Wishbone Rear Suspension and 18-Inch Wheels
LOS ANGELES. – Subaru of America, Inc. debuts the all-new 2008 Impreza WRX STI today at the Los Angeles International Auto Show. The ultimate performance Subaru is powered by a 305-horsepower Boxer engine and features a new level of driver-selectable powertrain- and dynamic handling-control. The 2008 WRX STI is built exclusively as an aggressively styled wide-fender 5-door model with a design strongly influenced by the brand’s competition heritage.
The 2008 WRX STI is the third-generation of the rally-bred supercar, which Subaru of America first launched to the U.S. market in 2004. Developed by Subaru Tecnica International, the high-performance and motorsports subsidiary of Fuji Heavy Industries Ltd., the WRX STI features an exclusive engine, drivetrain, suspension and interior.
The WRX STI’s revised 2.5-liter intercooled turbocharged Boxer engine, now with Dual Active Valve Control System (Dual AVCS), produces 305 horsepower (SAE) at 6,000 rpm, a gain of 12 over the previous model. The 290 lb.-ft. torque peak is the same as before but arrives at 4,000 rpm, which is 400 rpm earlier, for better response. Significantly, the more powerful 2008 WRX STI achieves the very stringent Bin 5 Tier 2-Federal (EPA) and LEV2-California Tier 2/Bin 5 emissions certification.
The Driver Control Center Differential (DCCD) version of Symmetrical All-Wheel Drive – which remains exclusive to the Impreza WRX STI – takes driver-controlled response to another level for 2008. The DCCD system now offers three selectable automatic performance modes in addition to the six manual differential-locking settings. For the first time, the DCCD AWD system integrates the Vehicle Dynamics Control (VDC) stability and traction control system, also with three driver-selectable positions.
The 2008 WRX STI offers 18-inch wheels as standard, featuring a new five-spoke design. Also available are optional 18 x 8.5 in. BBS® forged aluminum-alloy wheels. All 18-in. wheels wear Dunlop SP600 245/40R18 tires.
New side-curtain airbags are standard. A new convenience in the 2008 WRX STI is the Incline Start Assist feature, also shared with all Impreza models equipped with VDC. This system can momentarily prevent the vehicle from rolling backward when being driven away from a stop on an incline.
Even with the new, roomier 5-door body, special chassis reinforcements, new double-wishbone rear suspension and added safety features, the 2008 WRX STI (with the available BBS wheel package) weighs just 22 lbs. more than the 2007 WRX STI sedan. In addition, the 2008 WRX STI offers the added refinement instilled throughout the next-generation Impreza model line that was introduced for 2007.
COMPETITION-INSPIRED WIDE-FENDER DESIGN
The wide-fender 5-door body of the 2008 WRX STI draws design inspiration from the Subaru WRC Concept first shown at the Frankfurt Auto Show in fall 2007. The bulged fenders and rear quarter panels, along with the rear gate-mounted spoiler and aerodynamic ground effects, give the new WRX STI a direct link to Subaru competition cars. The hood scoop, brake-cooling air intakes and engine heat outlets are all functional. The rear gate spoiler integrates an LED high-mount stop lamp.
The standard high-intensity discharge (HID) low beams use manual height adjusters. Fog light insert covers add to the no-nonsense look, and fog lights are included with the BBS wheel option package. The scoop in the aluminum hood feeds outside air to an intercooler that is significantly larger than the intercooler used on the standard WRX. Making it easier to show off the impressive intercooled turbo Boxer engine are dual gas-strut hood supports instead of a prop rod.
A new aero package for the WRX STI was designed to reduce overall lift at high speeds. The front valance of the new WRX STI features a deep, aggressive front spoiler with side air vents to improve cooling. The front spoilers and front bumper flow into an STI-design aerodynamic ground effects package with side skirts. The rearmost edges of the front fender arches hide air vents that exhaust heat from the engine compartment. The 5-Door design features a distinctive sweeping character line that flows upward at the rear of the car and into the taillights.
The short rear overhang is accentuated by clear-lens LED rear lights and widened rear quarter panels that wrap into the STI designed rear bumper. Unique to the WRX STI, the lower rear fascia panel integrates cutouts for the quad exhaust tailpipe tips.
ALL-NEW PLATFORM AND DOUBLE-WISHBONE REAR SUSPENSION
The new Impreza WRX STI chassis improves crash-worthiness and provides a stiffer platform for crisper handling. The 103.3-in. wheelbase is 3.9-in. longer than the previous model to improve interior space, utility and ride compliance. The new chassis is designed for improved rigidity, incorporating high-tension steel at key structural points.
Solid engine mounts are used to minimize engine movement, and high-tension steel was added in suspension-mounting areas. New framed side windows – used on all Impreza models – also contribute to improved body rigidity and provide for a quieter interior with better window sealing.
A new double-wishbone suspension replaces the previous inverted-strut arrangement at the rear and features exclusive hubs and a wider track. Inverted struts used for the front suspension provide high bending resistance for quicker and more consistent performance under hard cornering. Aluminum front lower A-arms reduce unsprung vehicle weight.
The new suspension with special STI tuning along with the stiffer platform give the 2008 WRX STI the agile responses that have made this model a performance superstar. At the same time, the new WRX STI exhibits a more refined demeanor on any road. To further improve handling in the new WRX STI (and all Impreza models), the engine is now placed slightly lower in the chassis, lowering the center of gravity.
The quick-ratio steering system yields 2.8 turns lock-to-lock, and the steering rack uses a “cannon mount” for greater rigidity that improves on-center response. The powerful Brembo Performance Brake System employs ventilated 4-wheel Super Sport anti-lock (ABS) disc brakes with Electronic Brake-force Distribution (EBD). The braking system is enhanced in the new 2008 WRX STI with slightly larger rotors (see page 9 for more details).
The new body structure in addition allows the WRX STI to retain the useful 60/40-split fold-down rear seat without requiring additional structural bracing that might have been needed with the performance suspension and tires. The new design also helps to reduce noise, vibration, and harshness (NVH). The compact layout of the double-wishbone rear suspension results in less intrusion into the cargo area, providing a wider and deeper luggage compartment. The wide and flat load floor can accommodate two Tour-size golf bags with the rear seatbacks in the upright position.
SPORT-THEMED INTERIOR DESIGN
The 2008 WRX STI is 2.2 inches wider than the previous-generation model and offers improved hip and shoulder room. Larger door openings provide improved ingress and egress, and the rear doors open 75 degrees to allow for better rear seat access. The longer wheelbase (103.3 in.), contributes to improved rear seat legroom, and the rear seatback angles have been reclined for improved rear passenger comfort.
The 2008 WRX STI interior places a new emphasis on comfort and spaciousness while still conveying the model’s serious performance nature. New materials, including double-stitched fabrics and high-grade interior plastics, impart a feeling of higher quality. Even with the added refinement, the WRX STI preserves its rally roots, especially with the performance-design front seats that integrate the backrest and head restraint. The front and rear seats are upholstered in Graphite Gray Alcantara with Carbon Black leather-trimmed bolsters for optimal grip. The 3-spoke black leather-wrapped steering wheel tilts and telescopes and features cruise control and audio system buttons.
The sweeping twin cockpit design embraces occupants, and brushed aluminum-look insets flow into the center stack. The center console shape adds to the airiness of the interior, aided by the sculpted door panels and improved headroom. Each door panel houses a molded recess that can accommodate a 24-oz. soft drink bottle, as well as small items.
The instrument panel features electroluminescent gauges. As before, the indicator needles sweep the gauge faces upon engine startup. An illuminating STI badge in the center console is another new sporty touch. The instrument gauge cluster features a 9,000-rpm tachometer and a 160-mph speedometer. In between are indicators for the DCCD display, VDC mode and SI-DRIVE.
NAVIGATION AND HIGH-PERFORMANCE AUDIO
Standard amenities that make the WRX STI a great everyday driver include an automatic climate control system with cabin air filtration; a standard AM/FM premium stereo with 6-disc in-dash CD changer and 10 speakers, plus a vehicle security system with engine immobilizer. The Radio Broadcast Data System can display a variety of information, including a song’s title and artist.
For the first time, the WRX STI is available with an optional navigation system, which integrates a vehicle information center. The navigation screen is placed at the top of the dashboard for improved visibility and ease of use. All Impreza models equipped with the optional navigation system debut the first OEM mobile application of Audyssey MultEQ audio enhancement. Used in high-end home theater systems, Audyssey MultEQ creates the optimal sound experience for passengers in each seat position by tuning equalization that corrects for time and frequency response.
In addition to an input for MP3 players, the center console also includes video jacks that can accommodate portable gaming devices. These can be displayed on the navigation screen when the vehicle is parked. The WRX STI comes pre-wired for XM® or SIRIUS® Satellite Radio.
NEW SAFETY TECHNOLOGY
The new 2008 Impreza models utilize the proven Subaru Ring-Shaped Reinforcement Frame body structure with front and rear crumple zones. All Impreza models for 2008 gain standard side-curtain airbags. The Subaru Advanced Frontal Airbag System (SRS) features front seat side impact air bags. In the passenger side front seat, a sensor module detects weight – first determining if it is occupied, and if so by a child or adult – to control air bag deployment. As part of the system, the dashboard features an “Airbag” indicator light. There are 3-point seatbelts for all seats, including front height-adjustable seatbelts with electrically triggered pre-tensioners and force limiters.
Impreza WRX STI Core Technology
The 2008 Impreza WRX STI is far more than a modified version of the WRX. The two models share a basic architecture, some interior trim and little more. Nearly every major mechanical system in the WRX STI is unique to this model: engine, transmission, DCCD All-Wheel Drive system, special suspension, brakes, plus interior appointments.
Major Changes to Powertrain and Drivetrain for 2008
Subaru optimized the entire powertrain and drivetrain in the 2008 Impreza WRX STI to provide better performance and a greater degree of driver-selectable control. The heart of the Impreza WRX STI is a revised version of the 2.5-liter intercooled turbocharged Boxer engine used previously. The biggest change for the 2008 model is the addition of Dual Active Valve Control System (Dual AVCS) variable valve timing technology and the Subaru Intelligent Drive (SI-DRIVE) system.
Dual AVCS controls valve timing on both the intake and exhaust valves, compared to only the intake valves in the previous WRX STI. Dual AVCS adjusts intake and exhaust camshaft timing to employ the ideal intake and exhaust valve overlap under all engine operating conditions. The system helps eliminate the traditional compromise between low-end torque and high-rpm horsepower and also helps to enhance fuel economy and reduce emissions.
The Subaru Intelligent Drive (SI-DRIVE) technology adds a new dimension of driver engagement. The system essentially allows the driver to custom-tailor the car’s driving characteristics by choosing from among three selectable modes – “Intelligent,” “Sport” and “Sport Sharp” – using a rotary dial on the center console. By doing so, the driver is optimizing engine performance, control and efficiency.
Turbo Boxer Engine Proven on Road and Track
The 2.5-liter horizontally opposed (Boxer) 4-cylinder engine is based on a specially reinforced semi-closed deck engine block with high-strength cast pistons. A semi-closed deck design provides the same cooling efficiency as an open-deck cylinder block but with the higher strength of a full closed-deck. Special reinforcing ribs in the block provide additional strength, and the crankshaft is nitride-hardened. Compression ratio is 8.2:1, as in the previous model. The turbocharger in the WRX STI engine produces a maximum of 14.7 PSI of boost, compared to 11.9 PSI in the standard WRX.
Further enhancing quick throttle response in the WRX STI is a drive-by-wire Electronic Throttle Control (ETC). This system eliminates the physical linkage between the throttle pedal and the engine. The ETC system provides more precise control and more flexible response than a conventional throttle and also helps to reduce fuel consumption and emissions.
Iridium-tipped sparkplugs provide a more precise spark than platinum-tipped sparkplugs. A precious, silver-white metal, Iridium is one of the densest materials found on Earth. An Iridium-tipped sparkplug requires less voltage to spark, burns fuel more efficiently and sparks at leaner air/fuel mixtures to ensure optimal performance. The WRX STI exhaust system features a more efficient high-flow rear catalytic converter, low backpressure muffler and two sets of dual-outlet chrome tailpipes.
How SI-DRIVE Works
The SI-DRIVE system is integrated into the Engine Control Module (ECM). SI-DRIVE enables three distinctively different modes of vehicle performance characteristics by regulating the ECM and by fine-tuning the Electronic Throttle Control system. With Intelligent mode selected, the system reduces engine torque and maximum power and switches to a more relaxed throttle response curve. By controlling throttle angle and response of the Electronic Throttle Control system, SI-DRIVE restrains peak power and torque somewhat. Intelligent mode can provide smoother response while commuting in traffic, for example. In addition, Intelligent mode’s more relaxed responses and lower peak torque output can be used to complement the low-traction-surface driving safety provided by the All-Wheel Drive System. (Subaru recommends that WRX STI drivers install proper winter tires for snow conditions.)
Selecting “Sport” mode provides quick throttle responses and powerful, linear acceleration, making it ideal for everyday sporty driving. In “Sport Sharp” mode, SI-DRIVE modifies the engine’s electronic throttle mapping to deliver lightning-quick throttle response and put down the power sooner. As its name might suggest, Sport Sharp mode enhances the performance feel of the car and is ideal for tackling twisty roads.
Exclusive 6-Speed Manual Transmission
As before, the Impreza WRX STI comes equipped exclusively with a 6-speed manual transmission. Gear ratios remain the same as in the 2007 model. This unit is designed to handle high-torque capacity while providing short, smooth shifts. All gears are helical-type with diameters and thickness chosen for high-strength. Triple cone synchronizers on 1st (new) and 2nd gears, a double-cone synchronizer on 3rd gear and single-cone carbon synchronizers on all other forward gears help ensure durability. A parallel link gear selector shortens shift throws, and sliding bearings on the shift fork rods reduce friction.
Revised DCCD All-Wheel Drive with VDC
The 2008 WRX STI features an enhanced version of the Driver Controlled Center Differential (DCCD) All-Wheel Drive System. The DCCD system is one of the most advanced and most performance-directed AWD systems on the market, regardless of vehicle segment. The system employs planetary-type differential gears with a nominal 41:59 torque split. A mechanical limited-slip type center differential augments the electronically controlled differential to enhance torque transfer performance. A steering sensor input enhances torque transfer response by accurately relaying the car’s cornering situation.
The newly enhanced DCCD AWD System has three modes in the 2008 WRX STI: “Auto” is the same as in the previous model. The new “Auto (-) Active Sport setting shifts the torque bias to the rear and also opens the center limited-slip differential (no locking factor), which improves steering feel. For driving on slippery surfaces, such as gravel or snow, the Auto (+) setting tightens the LSD. The six manual differential locking settings also remain.
Set in “Auto” mode, the electronically managed continuously variable transfer clutch can vary the torque distribution ratio as needed to suit driving and road-surface conditions. Auto mode provides the best all-around performance for most drivers and circumstances, varying the front/rear torque distribution automatically via the limited-slip type differential, depending on driving conditions and driver input. The system determines the ideal power distribution in response to vehicle acceleration, deceleration, steering angle, cornering force and wheel slippage.
In manual mode, DCCD allows the driver to vary the front-to-rear torque distribution (up to 50:50 maximum) to optimize AWD performance for varying driving conditions. The driver first selects manual mode with a console-mounted button and then adjusts the rocker switch on the center console to select from among six levels of center differential locking. Increasing the lock factor keeps more power at the front wheels, which the driver might want in certain driving conditions, on particular roads or to suit an individual driving style. A helical-type limited-slip front differential and TORSEN® torque-sensing limited-slip rear differential optimize power distribution side-to-side, helping to prevent the inside wheels from slipping during cornering.
The WRX STI driver can also custom-tailor the level of dynamic intervention offered by the Vehicle Dynamics Control (VDC) system. There are three settings: “VDC Normal,” “Traction” and “Off.” The “Normal” setting will provide the highest level of system engagement, utilizing traction control (TCS) and VDC. The “Traction” setting is more performance-oriented, with less-restrictive VDC and the engine torque-reduction control disengaged. The “Off” setting will turn off the VDC and the traction control functions.
Brembo Brakes with Super Sport ABS
Subaru is again equipping the Impreza WRX STI with the advanced Brembo Performance Brake System, which employs ventilated 4-wheel disc brakes to help ensure stopping power and consistency commensurate with the vehicle’s high-performance capability. Rotors are slightly larger than on the 2007 model: The front discs measure 13.0 inches in diameter (vs. 12.77 in. before) and utilize 4-piston, fixed-position calipers. The rear discs are 12.6 in. diameter (vs.12.3-in. before) and use 2-piston, fixed-position calipers. The rear caliper pistons are larger in size to provide increased braking force.
Electronic Brake-force Distribution (EBD) helps to reduce stopping distances, and the Super Sport Anti-lock Braking System (ABS) helps to reduce understeer compared to conventional ABS systems. EBD provides precise control of braking pressure between the front and rear wheels based on the vehicle load to improve stability and stopping distances. Brake Assist analyzes the force and stroke on the brake pedal and increases hydraulic boost to provide enhanced emergency braking, also activating the ABS system early if needed.
Super Sport ABS, using input from a lateral g-sensor, a steering angle sensor, a yaw sensor and a brake pressure sensor, can control the braking forces at each rear wheel independently, optimizing braking ability during hard cornering to help reduce understeer. In contrast, conventional ABS systems control the rear wheels as a pair, reducing the braking force to both rear wheels equally.
About Subaru of America, Inc.
Subaru of America, Inc. is a wholly owned subsidiary of Fuji Heavy Industries Ltd. of Japan. Headquartered in Cherry Hill, N.J., the company markets and distributes all-wheel drive Subaru vehicles, parts and accessories through a network of nearly 600 dealers across the United States. Subaru is the only car company that offers Symmetrical All-Wheel Drive as standard equipment on every vehicle in its model line. Subaru, WRX, Impreza and STI are registered trademarks of Subaru of America, Inc.
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