No matter the model, the Subaru Impreza is extremely stable. All-wheel drive eliminates any hint of torque steer under hard acceleration.
Subaru Impreza RS, TS, and Outback Sport are powered by a 165-horsepower naturally aspirated horizontally opposed four-cylinder. WRX comes with a turbocharged and intercooled 2.0-liter engine that generates 227 horsepower, strong motivation to a 3100-pound car. WRX STi nails the needle to the peg with 300 hp from a 2.5-liter turbo and intercooled engine.
Four different types of all-wheel drive are used. Models with manual transmissions use a locking viscous center differential, while those automatic transmissions have Subaru's electronically controlled Variable Torque Distribution AWD. The WRX STi is equipped with a special heavy-duty six-speed manual gearbox and a driver-controlled center differential.
When the WRX was new, we called it "an absolute hoot to drive." But there's nothing like a generous dollop of horsepower in a compact chassis to twist the excitement dial over to the right and, with 300 horsepower, the STi boasts a power-to-weight ratio that humbles expensive sports cars and sports sedans.
Upon start up, the STi has the familiar and friendly Subaru vibrations, a distinctive feature of a horizontally opposed four-cylinder engine. The controls are light and the pedals well spaced; only a distinctly audible basso exhaust note hints that the STi is anything but an ordinary Impreza.
Once under way, the STi reveals that it is anything but. There's a tense feel to this engine even at part throttle, like it's ready to run. The heavy-duty gears in the transmission, exclusive to the STi, whine faintly, something Subaru didn't try to hide. Drive it over 3000 rpm and the turbo boost starts to rise, even with the gas pedal well off the floor, and the engine wants to surge the car forwards. The STi yearns to run. Slam the pedal to the floor and the STi grips and goes. The engine is louder than the WRX's but never gets raucous. It definitely does sound like a very serious Subaru.
(Technical stuff: Look under the hood. The intercooler, emblazoned with the STi logo, rests atop the engine like a crown. It cools the intake charge after it is compressed and heated by the turbocharger. The turbocharger is tucked behind and to one side of the engine. An unusual feature is a catalytic converter between the engine and the turbine. There are two more cats in the exhaust behind the turbo. The engine features dual overhead camshafts with four valves per cylinder with Subaru's Active Valve Control System variable valve timing, and solid lifters for reliable high-rpm operation. Throttle is electronic drive by wire.)
The WRX engine reaches its power peak at 6000 rpm and is redlined at 7000 rpm; maximum torque comes at 4000 rpm. Knowing how quickly this engine can rev to redline, Subaru has a buzzer that can be set to alert the driver to shift before the engine bumps up against its rev limiter. Gear ratios on the six-speed manual gearbox are well matched to the engine's torque curve, with second gear good to the high side of 60 mph. The shifter is quick and accurate and the transmission always willing to go to the next gear.
We had the opportunity to drive the STi on a road course. In all honesty, it's more at home there than on the highway, unlike most cars. The STi has all-wheel drive, like all Subarus, but its unique Driver Control Center Differential has a base 35/65 torque split between the front and rear. In automatic mode, an electronically managed continuously variable transfer clutch changes this ratio as needed to maintain the best ratio of grip between the front and rear wheels. The driver can choose, however, to vary this manually with a thumbwheel on the center console. We found it best, however, to let the computer do its thing. On the racetrack, it was infallible in divvying out the grip to the front and rear axles, which have limited slip differentials to maximize grip between left and right.
With its nominal rearward torque bias, the STi's suspension has been tuned to provide minimal understeer. Its turn-in, a racer's term for how well the car responds to steering wheel input at the start of a turn, is crisp. In transients, the shift of weight from one side to the other in S-curves, the STi is smooth and well controlled. The WRX STi has inverted MacPherson struts, with the damper body on top rather than on bottom, which allows a stiffer strut for better camber control and more accurate steering.
With the grip of all-wheel drive and its big and sticky tires, the STi launches from corners. Braking is like throwing out the anchor, thanks to the race-ready Brembo disc brakes at all four wheels, plus four-channel ABS that actuates the brakes of each wheel independently (most four-channel systems read all four wheel separately, but apply ABS to both of the rear wheels together). The brakes, no matter how hard you use them, are absolutely fade proof, even on the racetrack. Subaru has learned the hard lessons of world-class rallying well.
Around town, the STi's ride quality is extra firm. The short 100-inch wheelbase and sports suspension make a luxurious ride impossible. Buyers wanting a boulevard ride ought best look elsewhere, which no doubt they will. Textured pavement generates noticeable road noise in the cabin, but while the WRX never felt harsh, the STi is not for the faint of heart.
Wind noise is almost nonexistent. While there's no audio system in the STi, the true enthusiast will appreciate the mechanical sounds generated by this minimally disguised racecar. On the STi, we noticed hood flutter at speed. No doubt enthusiasts will cherish the shaking of lightweight aluminum hood, a reminder of the car's performance capabilities.
We've driven the WRX over rough roads, the kind they use for special stages in rallies. We beat the WRX like a living room rug over a clothesline and it never shook or shuddered, much less fell apart like it should have done. We came away impressed, not only that the Impreza wasn't shedding parts, but also that it felt as solid as chunk of concrete. That boded well for the long-term durability of all the Impreza models, which are built on the same solid chassis.
The Sti, on the other hand, is not designed to be driven on gravel stages because of its low ride height. Therefore, rally competitors gravitate to the 227-hp WRX instead.
All of the Impreza models are firmly packed with technology, so they weigh a little more than other subcompacts. According to Subaru, the all-wheel drive, the fully independent suspension, the chassis, and the turbo have all been put on a gram-by-gram diet. The chassis was made as light as possible, with competition in mind, using tailor-welded blanks (essentially, thicker metal only where it's needed). The STi even has a lightweight glass rear window. Still, though the STi weighs in at over 3000 pounds, it has a power-to-weight ratio rivaling the V8-powered 2004 Audi S4.
Ride quality has been improved for all Impeza models except the STi, which has special struts, by using multiple-phase valves in the suspension struts.
The Impreza 2.5 RS can be considered WRX Lite. With 165 horsepower and, just as important, 166 foot-pounds of torque on tap, it will suck the headlamps from the 120-horsepower Mitsubishi Lancer OZ, the 130-horsepower Mazda Protege, and the Ford Focus ZX3. More potent competitors include the 160-horsepower Acura RSX and the 180-horsepower Volkswagen GTI 1.8T. While the Subaru benefits from all-wheel drive, these other cars muddle through with front-wheel drive. Best of all, the RS comes with the same spirit as the WRX, only with a few ponies less for more affordability.
The same spirit comes in subcompact wagon form in the 2.5 TS Sport Wagon. Both the RS or TS cost about $5,000 less than a WRX, and they are likely less expensive to insure than the powerful WRX.
The WRX STi is another matter altogether. It will be lusted after by a demographic that is still in the high insurance rate age group, there's a psychographic group that will not doubt consume the 300 per month allocated among Subaru's 525 U.S. dealers. The WRX STi will compete directly against the 271-horsepower Mitusbishi Lancer Evolution, another rally-derived subcompact sedan.