Zipping through a narrow canyon course etched into walls of granite, a street-legal rally car flows with the twisties on the Ortega Highway, California 74, which runs across the Santa Ana Mountains from the Pacific Coast at San Juan Capistrano to Lake Elsinore.

Actually, we're flying through this convoluted course, working the sporty Momo steering wheel and plying a Prodrive six-speed gearbox with the turbo-charged and inter-cooled engine whining and Potenza rubber wailing, all simply to see just what this thing can do.

And it can do a lot.

We're talking pin-your-ears-to-the-seat accelerations and king-of-the-street speeds in a relatively lightweight four-door package patterned after World Rally Championship (WRC) race cars.

This turbo-charged sports sedan from Japanese automaker Subaru is called the Impreza WRX STi.

It's based on the subcompact Impreza platform and derived from Subaru's WRX performance car but with more juice from a larger engine and more sporty paraphernalia to cede no street race from "The Fast and the Furious" crowd.

Those STi initials on souped up WRX signify Subaru Technica International, the motorsports division of Subaru and the force behind Subaru's trophy-collecting rally cars.

What's a rally car?

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 race 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 multiple wins, thanks to the wily nature of Subaru rally cars spinning off the Impreza platform.

The new 2004 WRX STi, also using the Impreza as its foundation, emulates those Subaru rally cars, only without roll bars and five-point safety belts.

In fact, Subaru's current WRX rally race car is based on the production model WRX.

Differences between street car and rally racer concern special modifications to the engine plus the addition of heavy-duty and adjustable suspension components, special seam welding of the structure to endure harsh punishment on a rally course, and the rally roll cage.

The STi edition varies from production model WRX in terms of powertrain and gearbox, with special mechanical equipment added to enhance performance and handling.

Displacement increases over the WRX plant, rising from 2.0 liters to 2.5 liters. That's the largest displacement ever for a WRX STi model and it goes exclusively to the North American market. It's also the most powerful four-pack in America, thanks to a turbo-charger and inter-cooler aboard to boost output and score some awesome muscle numbers.

It makes an incredible 300 hp at 6000 rpm plus as much torque as 300 lb-ft at 4000 rpm. The boxer engine has a reinforced block with forged aluminum alloy pistons and carbon steel connecting rods. Then Subaru adds the active valve control system (AVCS) variable valve timing to optimize engine efficiency. STi's turbo-charger comes directly from Subaru's WRC racers with the boost climbing to 14.5 psi, while a big-capacity inter-cooler uses a manually-controlled water spray for additional cooling.

All of that power channels through a close ratio manual six-speed transmission developed by Prodrive. The tight-shifting stick contains double-cone synchronizers for first, third and reverse gears, plus a triple-cone on second and an internal oil pump for heavy-duty workouts.

There's no choice about the traction mechanism, however, as all of the vehicles that Subaru ships to America arrive with an all-wheel-drive (AWD) system that's always engaged. Torque muscle from the turbo-charged engine moves directly through an electronically-controlled intelligent transfer case to whichever wheels can maintain a bite of traction, with scant loss of energy in the process.

Subaru's driver control center differential (DCCD) enables the STi driver to manually manage torque directed to front and rear wheels for performance handling. Set the DCCD in automatic mode, however, and it will distribute the torque in various ways based on the driving conditions. Further, the STi uses a limited-slip differential in front and back for additional tire traction.

A super-stiff body structure from Subaru's ring-shaped reinforcement frame contains a hydroformed front subframe with the four-wheel independent suspension system derived from Subaru WRC competition cars but tweaked for tight cornering control on paved roads.

It's similar to the suspension on WRX, only dropped by almost half an inch to set up a lower center of gravity. And to rein all of those STi horses, there are serious brakes aboard with huge Brembo discs visible between aluminum spokes of the 17-inch BBS wheels.

Treads on the pavement consist of wily Bridgestone Potenza RE070 tires at 225/45ZR17. Brakes link to electronic brake-force distribution (EBD) and a new anti-lock braking system (ABS) capable of governing brake forces at each wheel individually.

Exterior styling for the STi, inspired by Subaru WRC racers, capitalizes on a wide wheel track with squarish blister fenders to bulge the front end plus a contoured aluminum hood supporting the enlarged air scoop.

A functional cockpit design positions two bolstered buckets beside a central console housing the shifter stick. Steering wheel is a three-spoke Momo in gray leather with red stitching and it makes only three turns lock-to-lock.

The bottom line: MSRP for racy WRX STi is $30,995.

Click here for more information on the Subaru WRX STi.
For the Subaru 2004 Model Guide : Click Here