The 2011 WRX continues to get a 265-horsepower, 2.5-liter horizontally opposed (boxer) four-cylinder engine and five-speed manual transmission, with viscous-differential all-wheel drive, while the STI gets a 305-horsepower, 2.5-liter turbocharged boxer four, six-speed manual transmission and an all-wheel-drive system that includes the Driver-Controlled Center Differential (DCCD). Worth noting is that the former Impreza GT model with the four-speed automatic has been dropped. That leaves an all-manual lineup for the WRX and STI, a factor that might be a deal-breaker for some.
Even before looking at what the STI's extra toolkit does, there remains quite a difference between these two models, just in the way they respond to your right foot—even in how they sound. Start the STI up and take off gently and the engine sound is deep and pulsating, with more of a tuner note; the WRX sounds more like a 'normal' car. Indeed, these two models have very different tuning, and the uninitiated might think, at first impression, that the WRX has the stronger engine. It's a little deceiving that both engines are listed as producing their peak torque at 4,000 rpm, and the STI produces a peak boost of 14.7 psi, versus 14.2 psi, but the STI's engine saves it all for the upper ranges. Shift a little too early and the STI feels almost sluggish, but keep the revs up and somewhere north of 3,500 rpm it'll suddenly pin you back in your seat.
Fortunately, the six-speed manual has closely spaced gears, and once you're on top of that peak boost you can keep it close. The WRX, by comparison, comes on smoother, torquier, in a way you can feel a full 1,000 rpm lower; and the combination of slightly larger gaps between gears makes it feel more docile, more flexible, though ultimately less aggressive.
Only in the STI, an SI-Drive controller lets you select Intelligent (I), Sport (S), or Sport Sharp (S#) modes, each affecting throttle response. Larger Brembo performance brakes are included with the STI as well, and a Super Sport ABS system allows independent control of each rear wheel and reduces understeer. And the stability control system includes a 'traction' mode, intended for the track, that uses the brakes but no longer cuts the throttle; it can also be turned off completely.
There's a real difference in the way the WRX and STI ride and handle, too. While the STI's setup feels tight and well controlled in almost every case, and the WRX continued to surprise us with its poise, the WRX has a little more bounciness, a little more lift and squat during extreme maneuvers. Both models, by the way, benefit from an inch more of rear track, and the WRX has stiffer rear bushings and new, lighter 17x8 Hitachi wheels.
While the WRX's suspension layout has been mostly carried through, there are some major changes in the STI's suspension. With some clever engineering, Subaru has managed to stiffen springs, bushings, and stabilizer bars, and lower ride height, without making the in-cabin experience any harsher. The key to this is a new pillow-ball bushing setup—at steering pivot points—that essentially helps isolate road harshness while preserving the responsive, communicative feel just at turn-in (and preserving the geometry off-center) that would lead to more driver confidence. It's a solution borrowed from racing cars that, in the STI, is the perfect solution, and Subaru says it provides more stiffness on the track and reduces understeer in cornering.
What it all means, based on our driving experiences on-road and on-track, it that Subaru has been able to tune the suspension to be stiffer and lower while keeping the steering feel just right; it gives enough road feel yet doesn't kick hard. The STI's willing partner is the DCCD system, which sends 41 percent of torque to the front wheels and 59 percent to the rears. There's an Auto, Auto+, Auto-, and six levels of manual center-diff lockup, all accessed through a little flip switch in the center console. Though we drove on the road for most of the time in the Auto mode, on the track we were able to get that rotation, and feel the tiny bit of power oversteer, in Auto- and the Traction mode.
The 2011 WRX keeps it simpler—and, some might say, more enjoyable—skipping the DCCD, SI-Drive, and trick new front suspension. Pick the right gear coming into a corner and the WRX will slingshot you out of it, scrabbling for more grip than you knew was there. Blip the throttle while braking—the pedals are well-spaced, even for big feet—and drop a gear or two, trailing off the brake as you turn in, and there's no understeer, no tendency to push when it should grip. Do it right and you can even induce a little four-wheel slide just about anywhere you'd like, perfectly controlled and very neutral.