2015 Subaru WRX STI – Quick Takes

Subaru of America, Inc. has introduced the all-new 2015 WRX STI, its iconic performance flagship model, matching the proven 305-horsepower turbocharged BOXER engine and advanced drivetrain to a new, stiffer high-performance chassis and an aerodynamically enhanced wide-body sedan design. Subaru will offer a WRX STI Launch Edition, limited to 1,000 units and exclusively featuring WR Blue paint and gold BBS® forged alloy wheels and unique interior trim. This model’s striking appearance recalls the livery of the Subarus that won the World Rally Championship three times.

The WRX STI provides a rally-bred drivetrain and all-wheel drive handling that is unique to this model. Handling is enhanced with a stiffer chassis, firmer springs and faster steering (13.0:1 ratio). New for the 2015 WRX STI, Active Torque Vectoring joins the model’s arsenal of proven handling technologies that includes Multi-Mode Driver Controlled Center Differential (DCCD) Symmetrical All-Wheel Drive, Multi-Mode Vehicle Dynamics Control, and a Brembo® Performance Brake System with Super Sport ABS. Curb weight for the 2015 WRX STI is just two pounds more than for the 2014 model, thanks to the use of more high-tensile steel and an aluminum hood.

The 2015 WRX STI carries its bold personality inside, where new Alcantara® seating surfaces accented by red and black leather bolsters and red stitching set the tone for the upgraded and roomier cabin. A driver-focused interior remains integral to the WRX STI performance character, with the new model debuting a motorsports-inspired flat-bottom steering wheel and new whiplash-reducing performance-design front seats with height and tilt-adjustable head restraints. A wide array of new user technologies include, for the first time in a WRX STI, availability of a harman/kardon® premium audio system.

The 2015 WRX STI takes its motorsports pedigree to the road. Many know that the WRX STI won the World Rally Championship three times. More recently, Subaru expanded the WRX STI’s competition purview to include long distance road racing. While many brands tout performance-car development on Germany’s Nurburgring racetrack, the Subaru WRX STI won the SP3T class in the track’s grueling 24-hour race in 2011 and 2012 and took second place in 2013. A specially prepared 2015 WRX STI will compete in the 2014 race.

Iconic STI Design Exclusively in Sedan Form

A bolder front design makes the 2015 WRX STI look ready to devour the road. The “nose-cone” configuration combines the grille and bumper cap into one unit ahead of the hood, which for the 2015 model is made from aluminum to reduce weight over the front of the car. Narrower headlights, designed to evoke a raptor’s stare, flank the Subaru hexagonal grille. New standard LED low-beam headlights make it a more powerful stare.

The special hood, fenders, doors and quarters, bumpers, headlights and taillight clusters convey the WRX STI identity. As on previous WRX STI models, a functional hood scoop supplies the intercooler with fresh air, and in the 2015 model it is set more deeply into the hood to provide better forward visibility.

Other new performance-oriented details include foglight surrounds with a carbon fiber-like pattern and front fender vents that feature a mesh screen. A full aerodynamic body package includes the large trunk spoiler that has been a WRX STI signature feature. A rear diffuser, LED taillights and LED center high-mount stop lamp (CHMSL) leave a distinctive signature.

New, Stiffer Chassis for Greater Handling Agility

The aluminum BOXER engine and simple, symmetrical drivetrain layout help to lower the WRX STI’s center of gravity, a trait that contributes to its sporty handling characteristics. The springs, dampers, crossmembers, subframe bushings, and front control-arm bushings and attachments are all stiffer than in the previous model, paying dividends in sporty handling.

As a result, the WRX STI delivers ultra-crisp handling along with ride compliance that makes it suitable for everyday driving. The body structure makes greater use of high-tensile steel than the previous model and features special stiffening elements at key locations. Solid rubber engine mounts help to minimize engine movement, which in turn enhances handling agility.

The stiffer chassis helps yield a super-quick steering response that was benchmarked against top-handling sports cars. The hydraulic power-assisted steering uses a 13.0:1 ratio for 2.5 turns lock-to-lock, providing exceptionally quick response. (By comparison, the standard WRX model uses a 14.5:1 steering ratio for 2.8 turns lock-to-lock.)

As on previous WRX STI models, the 2015 version uses an exclusive inverted-strut front suspension system that provides higher levels of cornering agility. These struts exhibit high bending resistance for quicker and more consistent performance under hard cornering. Aluminum front lower L-arms reduce unsprung vehicle weight. Compared to the previous WRX STI, the 2015 model’s inverted struts feature thicker outer tubes, and the aluminum alloy lower control arms use pillow ball-type joint bushings and pillow ball-type joint mounts. The rear suspension lateral links also use this type of bushing.

The STI-tuned suspension teams with standard 18-inch wheels and 245/40R18 summer performance tires, with the WRX STI Launch Edition and WRX STI Limited models featuring BBS forged aluminum-alloy wheels (gold-painted on Launch Edition).

Exclusive to the WRX STI, the Brembo® Performance Brake System uses ventilated 4-wheel Super Sport anti-lock (ABS) disc brakes with Electronic Brake-force Distribution (EBD). Front discs measure 13.0 inches in diameter and use 4-piston calipers; the 12.4 in. rear discs use 2-piston calipers. Taking input from a lateral g-sensor, a steering angle sensor, a yaw sensor and a brake pressure sensor, Super Sport ABS can control the braking forces at each rear wheel independently, which optimizes braking ability during hard cornering to help reduce understeer.

305-hp Turbo BOXER Engine 

The 2015 WRX STI is powered by a 2.5-liter turbocharged/intercooled 4-cylinder BOXER engine that employs the Dual Active Valve Control System (Dual AVCS). The engine, which is exclusive to the WRX STI, produces 305 horsepower (SAE) at 6,000 rpm and 290 lb.-ft. of peak torque at 4,000 rpm.

The WRX STI 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. The turbocharger produces a maximum of 14.7 PSI of boost. The WRX STI’s efficient exhaust system emits a distinctive growl through signature quad tailpipes.

The WRX STI is equipped exclusively with a specially reinforced 6-speed manual transmission, which includes an STI short-throw shifter in the Launch Edition model. Incline Start Assist can momentarily prevent the car from rolling backward when being driven away from a stop on an incline.

The Subaru Intelligent Drive (SI-DRIVE) powertrain management system allows the driver to 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. SI-DRIVE alters vehicle performance characteristics by regulating the engine control module and by fine-tuning the electronic throttle control system.

With Intelligent mode selected, SI-DRIVE provides a more relaxed throttle response curve, making it useful for commuting in traffic, for example. “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 super-quick throttle response and put down the power sooner.

New Active Torque Vectoring

Active Torque Vectoring, a new enhancement of the Multi-Mode Vehicle Dynamics Control (VDC) stability and traction control system, can apply brake pressure to the inside front wheel to facilitate more neutral cornering. The VDC system offers yet more driver choices, with three settings: “Normal,” “Traction” and “Off.” The “Normal” setting provides the highest level of system engagement, utilizing traction control (TCS) and Vehicle Dynamics Control (VDC). The “Traction” setting is more performance-oriented, employing less-restrictive VDC and disengaging the engine torque-reduction control. The “Off” setting disengages the VDC and the traction control functions. Active Torque Vectoring remains engaged for “Normal” and “Traction” modes.

Multi-Mode DCCD All-Wheel Drive

The 2015 WRX STI is exclusively equipped with the Multi-Mode Driver Controlled Center Differential (DCCD) version of Subaru Symmetrical All-Wheel Drive. This sophisticated system uses planetary-type center differential gears with a nominal 41:59 torque split. A mechanical limited-slip type center differential augments an electronically controlled center differential to enhance torque transfer performance.

Sensor inputs that include steering angle, throttle position, RPM, lateral-g, yaw, brake, ABS and wheel speed govern torque transfer response. A helical-type limited-slip front differential and a TORSEN® torque-sensing limited-slip rear differential optimize side-to-side torque distribution, helping to prevent the inside wheels from slipping during cornering.

The DCCD AWD system features three automatic modes, each applying a different degree of center differential locking to match different driving situations. “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 center differential in response to vehicle acceleration, deceleration, steering angle, cornering force and wheel slippage. The “Auto -” mode makes less use of the center limited-slip differential (less locking factor) and holds the torque bias to the rear more frequently, which yields more handling-oriented steering characteristics. For driving on slippery surfaces, such as gravel or snow, the “Auto +” setting tightens the LSD.

In the DCCD AWD system’s manual mode, the driver can select one of six center differential locking levels (up to 50:50 maximum) to optimize AWD performance to suit the driving situation and surface conditions.

Roomier, Premium Cabin

A one-inch longer wheelbase than the previous WRX STI helps provide a roomier cabin in the new model. New available Welcome Lighting responds to the driver approaching the car. The windshield is more raked than before, with the narrower A-pillars pulled forward nearly eight inches at the base for better forward visibility, aided by a lower dashboard. Lower side sills and wider-opening doors make ingress/egress easier. Rear seat legroom is increased by nearly two inches, and trunk capacity is now 12 cu. ft., up from 11.3 cu. ft. in the previous WRX STI sedan. A standard 60/40-split fold-down rear seat extends versatility.

The new flat-bottom, leather-wrapped tilt/telescoping steering wheel integrates switches for audio and Bluetooth® controls. Whiplash-reducing front performance design seats feature separate tilt- and height-adjustable head restraints, a change from the seats with integrated head restraints used in the previous WRX STI.

The STI Design electroluminescent gauge panel gets a new 3.5-in. central LCD screen that displays various functions, including low-level warnings for oil and windshield washer fluid and the selected gear. Rich-looking appointments and details abound, including soft-touch materials for the dashboard, door trim and center console armrest. A new multi-information central display with 4.3-in. LCD screen provides a multitude of vehicle system functions, including a standard rear camera display, a boost gauge display, outside temperature, audio information (on non-navigation models), Bluetooth and climate control settings, and a VDC screen showing traction control operation. The display can also provide a vehicle self-check and maintenance reminder.

The 2015 Subaru WRX STI comes with the highest level of amenities ever for this performance flagship model. Standard features for the 2015 WRX STI include dual-zone automatic climate control and the All-Weather Package (dual-mode heated front seats, heated exterior mirrors and windshield wiper de-icer). The new standard audio system combines AM/FM stereo with HD Radio®, a single-disc in-dash CD player, 6 speakers, MP3/WMA capability, Radio Data Broadcast System (RDBS), Bluetooth hands-free calling and audio streaming, iPod® control capability, iTunes® Tagging, SiriusXM® Satellite Radio (subscription required), USB port and a 3.5mm auxiliary audio input jack. Numerous compartments located in and around the center console hold phones, USB drives and MP3 players.

An available touch-screen navigation system displays on a 6.1-inch LCD screen and offers voice controls. The WRX STI Limited model adds the luxury of leather-trimmed upholstery, an 8-way power driver’s seat, the harman/kardon premium audio system and a power moonroof that opens one inch farther than on the previous model.

Subaru Safety 

Subaru’s renowned safety package uses the brand’s proven Ring-shaped Reinforcement Frame body structure, which has been shown to excel in the new small overlap test by the Insurance Institute for Highway Safety (IIHS). In the cabin, a new driver’s knee airbag is added to the WRX STI’s roster of safety features that includes front side pelvis/torso airbags and side curtain airbags that offer front and rear outboard seat coverage.

Subaru produces a full line of all-wheel drive sedans, crossovers and SUVs, along with the rear-wheel drive BRZ sports car.

WATCH STEVE HAMMES FIRST LOOK AT THE 2015 SUBARU WRX STI 

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