Subaru WRX STI rally cars tote turbo power and AWD traction
Bob Plunkett, Sat, 11 Sep 2010 07:01:48 PDT
BASALT, Colo. -- Driving like a heavy-on-the-pedal rally racer, we whip the leather-bound steering wheel of Subaru's new street-legal rally car to the right, then to the left, then right again to hold a tight line on zigzag Fryingpan Road that follows the white-water Fryingpan River through a deep canyon in the Rocky Mountains of Colorado.
To tell the truth, we're taking the wiggly river road at lightning-quick speed -- sorry, Officer, but this car simply won't go slowly -- while plying the short-throw stick of a six-speed manual gearbox with a turbo-charged boxer engine spooling huge boost numbers and speed-rated tires (245/40R18 Dunlop SP Sport 600 summer performance tires wrapped around BBS forged-alloy wheels) bonding to blacktop at all posts, thanks to Subaru's all-wheel-drive system.
We're talking pin-your-shoulders-to-the-seat accelerations and king-of-the-street speeds in a relatively lightweight and compact-class package patterned after World Rally Championship (WRC) race cars.
The turbo-charged performance car from Japanese automaker Subaru is called the Impreza WRX STI.
Editions of 2011 conform as a wide-body five-door hatchback and a new wide-body four-door notchback sedan.
Both versions are 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 initials signify Subaru Technica International, the motorsports division of Subaru and the force behind Subaru's trophy-collecting rally cars.
It's a race car usually of small scale with some stock equipment aboard but also a high-output engine and modifications for added safety like a protective roll cage and five-point racing harnesses for the two front seats.
Rally races pit a driver and co-pilot/navigator in a special rally car against a stopwatch and detailed route maps, with daredevil competitors tearing across treacherous roads through cities and countryside, each vying to nail all checkpoints on time and beat the clock across a finish line.
Beyond North America in countries around the world, automobile rally racing receives the kind of sports attention that football fans in the United States reserve for contests like the Super Bowl. And in the WRC Subaru has racked up many wins, thanks to the wily nature of Subaru rally cars spinning off the Impreza platform.
The 2011 WRX STI, also using the Impreza as its foundation, emulates those Subaru rally cars, only without roll bars or five-point safety harnesses aboard.
The STI edition varies from a production model WRX in terms of powertrain and gearbox, with special mechanical equipment added to boost performance and handling, and specific body enhancements.
Special STI design features for the shell 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, engine heat outlets cut into flanks and side moldings applied for aerodynamic ground effects.
Up front, the 2011 STI models wear wider blacked-out foglamp nacelles, a jutting lip spoiler and a redesigned grille with black grille inset.
The contoured aluminum hood supports a functional air scoop just ahead of a raked windshield.
But everything about this vehicle revolves around the amazing engine tucked below the STI's front deck.
The plant 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-four engine's vibrations.
Displacing 2.5 liters, the aluminum-block engine has aluminum cylinder heads and dual overhead camshafts (DOHC) plus Subaru's dual active valve control system (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 six-speed transmission.
There's no choice for the traction mechanism, as all of the vehicles that Subaru ships to North America arrive with an all-wheel-drive system that's always engaged.
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.
A super-stiff body structure from Subaru's ring-shaped reinforcement frame contains a four-wheel independent suspension system with inverted-strut front suspension using forged aluminum-alloy lower A-arms and a double-wishbone rear suspension with STI-designed aluminum components.
The performance brake system by Brembo sets ventilated discs at all posts with four-piston calipers in front and dual-piston calipers in back. Brakes tie to a four-wheel sport anti-lock braking system (ABS) with electronic brake-force distribution (EBD) and electronic brake assist (BA) to enhance stability under hard braking maneuvers.
A functional cockpit design positions two bolstered buckets beside a central console housing the shifter stick. The steering wheel is a three-spoke design wrapped in leather with tabs to work the audio system, cruise control and Bluetooth hands-free phone link.
Standard content includes an automatic climate control system, aluminum-alloy pedal covers, electroluminescent instrument gauges, power controls for windows and mirrors and door locks, checkered carbon black upholstery with red stitching and a six-speaker audio kit with AM/FM/CD/MP3/USB.
A new WRX STI Limited model for the four-door sedan adds a power moonroof and leather seat upholstery.
Subaru sets the MSRP for a 2011 WRX STI 4-door sedan at $33,995, or $35,995 for a 5-door hatchback with the 18-inch BBS forged-alloy wheels.