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New WRX STI Chassis Tuning for 2011
The Subaru WRX STI was
already a highly optimized performance machine. Changes in chassis tuning for
2011 reflect both owner / enthusiast feedback and the brand's commitment to
keeping this model at the peak of the segment's performance offerings. The
fundamentals remain the same as before, but specific tuning - previewed by the
2010 WRX STI Special Edition - results in reduced body roll, more neutral
handling response and higher lateral-G capability.
The basics: The WRX
STI delivers ultra-crisp handling along with everyday ride compliance.
High-tensile-strength steel is used at key structural points and the
suspension-mounting areas. Inverted struts used for the front suspension provide
high bending resistance for quicker and more consistent performance under hard
cornering. Aluminum front lower L-arms reduce unsprung vehicle weight.
Major changes to suspension tuning for the 2011 WRX STI include a lowered ride
height and new pillow-ball bushings in front and stiffer bushings for the rear
subframe that supports the double-wishbone suspension - these improve camber and
toe stiffness. Both the front and rear suspension systems employ higher-rate
springs and thicker front and rear stabilizer bars than the 2010 model. Spring
rates have increased by 15.6 percent in front and 53 percent in the rear.
New standard 18-inch aluminum wheels feature high-luster paint and weigh
17.6 lbs less than the previous standard wheels. The optional 18 x 8.5 in. BBS
forged aluminum-alloy wheels are highlighted by silver high-luster paint for
2011. These wheels further reduce unsprung vehicle weight. Dunlop SP600 245/40
R18 summer performance tires are used with the standard and optional wheels.
Performance Evolution
The 2011 WRX STI continues as the
ultimate-performance Subaru with its high-boost 305-hp turbocharged/intercooled
Boxer engine teamed with a 6-speed manual transmission and the exclusive
Multi-Mode Driver Controlled Center Differential (DCCD) version of Symmetrical
All-Wheel Drive.
The WRX STI is equipped with advanced dynamic control
systems, including Subaru Intelligent Drive (SI-DRIVE) and Multi-Mode Vehicle
Dynamics Control (VDC) system, which features a track performance-optimized
mode. Incline Start Assist, featured on all Impreza models equipped with a
manual transmission, can momentarily prevent the vehicle from rolling backward
when being driven away from a stop on an incline.
SI-DRIVE Gives WRX
STI Driver More Control
Exclusive to the WRX STI models, Subaru
Intelligent Drive (SI-DRIVE) technology 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 (ECM) 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.
Multi-Mode DCCD All-Wheel Drive with Three-Mode Vehicle Dynamics Control
As before, the 2011 WRX STI is exclusively equipped with the Multi-Mode
Driver Controlled Center Differential (DCCD) version of Subaru Symmetrical
All-Wheel Drive. The system employs planetary-type 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. A steering sensor input enhances torque transfer response
by accurately relaying the car's cornering situation. A helical-type
limited-slip front differential and a TORSEN torque-sensing limited-slip rear
differential optimize side-to-side power distribution, helping to prevent the
inside wheels from slipping during cornering.br>
TThe DCCD AWD system features three
automatic modes. "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 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
manual mode, DCCD offers six levels of center differential locking, allowing the
driver to vary the front-to-rear torque distribution (up to 50:50 maximum) to
optimize AWD performance for varying driving conditions.
The Vehicle
Dynamics Control (VDC) stability and traction control system is standard on all
Subaru models for 2010. It is important to note that, in Subaru vehicles,
traction control plays a second line of defense against wheel slip after AWD
torque distribution. In contrast, some All-Wheel Drive systems on the market
lack the performance advantage of a locking center differential and rely solely
on traction control to redistribute torque away from slipping wheels.br>
Exclusive to the WRX STI, the Multi-Mode VDC system offers the driver three
settings: "VDC Normal," "Traction" and "Off." The "Normal" setting provides the
highest level of system engagement, utilizing traction control (TCS) and 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.
AAlso 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,
fixed-position calipers; the 12.6 in. rear discs use 2-piston, fixed-position
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. In contrast, conventional ABS systems
control the rear wheels as a pair, reducing the braking force to both rear
wheels equally.
Sporty, Spacious and Versatile Interior
New
for 2011, the WRX STI interior is finished in black and silver to highlight its
sporty design. The color of each metallic part was unified to dark metallic and
sharp silver. Trim panels, steering wheel air bag cover and steering wheel
switches are now dark cast metallic.
The standard tilt and telescopic
steering wheel is a three-spoke, leather-wrapped design embossed with the STI
logo in its center. The wheel features control switches for Bluetooth hands-free
phone function. The WRX STI models are equipped with standard aluminum-alloy
pedal covers and driver's footrest. Performance-design front seats integrate the
backrest and head restraint into a single structure. The instrument panel
electroluminescent gauges use indicator needles that sweep the gauge faces upon
engine startup.
The compact layout of the double-wishbone rear suspension
helps to minimize intrusion into the cargo area, providing a wide and deep
luggage compartment. In the 5-door models, the wide and flat load floor can
accommodate two Tour-size golf bags with the rear seat backs in the upright
position. In the 4-door sedan model, which is 6.5-inches longer than the 5-door,
the extra space provides for a larger, deeper trunk that can accommodate three
Tour-size golf bags. A 60/40-split folding rear seat further boosts cargo
capacity and convenience, and the 4-Door also features a rear seat fold-down
center armrest.
Standard amenities that help make the WRX STI an
excellent everyday driver include an automatic climate control system with cabin
air filtration and an AM/FM stereo with single-disc CD player that features
Bluetooth audio streaming and hands-free calling, iPod control capability, a USB
port, 3.5mm aux. input jack and XM/SIRIUS satellite radio capability. A vehicle
security system with engine immobilizer is standard, as well. The optional
navigation system integrates a vehicle information center and Bluetooth
hands-free calling. 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. All WRX
STI models come pre-wired for XM or SIRIUS Satellite Radio.
Subaru Impreza WRX STI: Photo Gallery, Review (1/2) and Specifications