2015 Subaru WRX STI rally car recast with big turbo, AWD traction
Bob Plunkett, Mon, 03 Nov 2014 12:29:02 PST
STRAWBERRY, Ariz. -- A 2015 edition of the WRX STI, a turbo-charged high-performance rally car from Japanese automaker Subaru recast on a new platform with a stiffer and more agile chassis, races down a blacktop strip of Arizona 87 as it descends the Mogollon Rim escarpment in a series of hairpin curves that wiggle like a spaghetti noodle dangled over rocky ramparts.
Naturally, we're pushing the powerful throttle through infrequent straights on the canyon descent yet slicing each apex in cleanly carved turns while working the short-throw stick of a 6-speed manual gearbox and the pedal for a performance brake system by Brembo with the turbo-boxer engine spooling huge boost numbers and 245/40R18 summer performance tires clawing the asphalt at all posts, thanks to Subaru's symmetrical all-wheel-drive (AWD) system.
Count this one as the coolest street-legal rally car yet from Subaru.
The all-new 2015 WRX STI, conformed as a compact-class 4-door sedan, comes with a 104.3-inch wheelbase that measures a full inch longer than the previous WRX STI. The extra length ends up helping to stabilize the vehicle when rolling over road bumps but also brings more room in the 2+3-seat cabin.
Handling improves on the 2015 issue due to the stiffer chassis with firmer suspension springs and a faster steering ratio (13.0:1).
Based on the compact Impreza platform and derived from Subaru's WRX performance car but with more juice extracted from the engine and more sporty paraphernalia aboard to cede no street racer's challenge, the STI version derives its initialed name from Subaru Technica International, the motorsports division of Subaru and the force behind Subaru's trophy-collecting rally cars.
Special STI features range from wide-body front fenders and rear quarter panels to functional brake cooling scoops up front and a spoiler mounted on the back gate, foglight surrounds in a carbon fiber-like pattern, and the aluminum hood supporting a functional hood scoop to supply the intercooler with fresh air.
The amazing engine tucked below the STI's front deck has four cylinders opposed horizontally and set perpendicular to the drive line, then linked with equal-length drive shafts so pairs of cylinders act like boxers jabbing at one another in counterbalanced movements which negate the typical in-line-4 engine's vibrations. Displacing 2.5 liters, the aluminum-block plant has aluminum cylinder heads and dual overhead camshafts (DOHC) plus Subaru's dual active valve control system (D-AVCS) variable valve timing for intake and exhaust valves.
Thanks to the high-boost turbo-charger and a cross-flow inter-cooler aboard, the STI engine racks up some awesome muscle numbers. It makes 305 hp at 6000 rpm plus as much torque as 290 lb-ft at 4000 rpm.
All of that energy channels through a close ratio manual 6-speed transmission -- the sole shifter offered.
Subaru labels the AWD equipment on STI as Symmetrical All-Wheel Drive with Driver Control Center Differential (DCCD) and Vehicle Dynamics Control (VDC).
The multi-mode DCCD enables the STI driver to manually manage torque directed to front and rear wheels (up to 50:50 maximum) for performance handling. It has three performance modes plus six manual differential-locking settings.
Further, the STI uses a helical gear-type limited-slip differential in front and a Torsen torque-sensing limited-slip rear differential to optimize side-to-side power distribution and garner additional tire traction.
Active Torque Vectoring (ATV), a new feature on the multi-mode VDC stability and traction control system, can apply brake pressure to the inside front wheel to facilitate more neutral cornering. The VDC system now offers three driver-select settings: Normal/Traction/Off.
The brake system by Brembo sets ventilated discs at all posts with 4-piston calipers in front and dual-piston calipers in back. Brakes tie to a sport anti-lock braking system (ABS) with electronic brake-force distribution (EBD) to enhance stability under hard braking maneuvers.
A functional cockpit design positions two bolstered buckets beside a central console housing the shifter stick, followed by a 3-seat rear bench with 60/40-split seatback and rear legroom increasing by nearly two inches. The new flat-bottom steering wheel bound in leather has tabs to work the audio system, cruise control and Bluetooth phone link.
2015 Subaru WRX STI
Engine size: 2.5-liter
MSRP: Starting at $34,495
Horsepower: 305 horsepower
Curb weight: 3,386 lbs to 3,444 lbs
MPG: 17 city / 23 highway
2015 Subaru WRX STI Base
2015 Subaru WRX STI Launch Edition
2015 Subaru WRX STI Limited