Subaru STI Event at Suzuka Circuit

Subaru hosted journalists at Japan's Suzuka Circuit near Nagoya recently to demonstrate suspension components that will be marketed as part of an expansion of its Subaru Tecnica International division. Eventually, STI will offer complete vehicles, such as BRZ concept shown this week in New York. (See related article: Don’t count on seeing this track-ready lowrider at a Subaru showroom anytime soon. For the near term, the STI business plan will focus on expanded aftermarket parts. But Subaru executives here say a modified BRZ carrying STI badging will go on sale at some point.

The NY concept is slathered with lightweight carbon fiber, including the side-view mirrors, steering wheel, rocker panels, rear fascia and instrument panel.

STI Through the Years

The concept is intended to showcase STI’s engineering prowess and tuning capability. The division was formed in 1988 and has some 80 employees, including 50 engineers, at offices in Tokyo and Gunma prefectures.

STI always has been aligned closely with Subaru’s motorsports activities and later expanded into aftermarket parts and then complete vehicles. The first STI model, a Legacy Touring wagon, was limited to 200 units in the home market in 1992.

More recently in the U.S., the WRX STI has been a tightly sprung lightweight hatchback or sedan making at least 300 hp and immediately recognized for its large rear wing. The car’s moderate price tag and all-wheel drive have made it popular among young male rally fans over the years. For a short time, the car was known solely as the STI, without the WRX prefix.

But Japan and a few other markets have seen a wider array of limited-edition performance variants getting the STI treatment, such as the Legacy tS, Forester tS and BRZ tS.

Again, it’s not about additional horsepower or torque but the application of patented STI-designed chassis and suspension hardware, such as front flexible tower bars, flexible draw stiffeners at both the front and rear, pillow-ball bushings at the rear and a flexible support rear subframe.

On a handling track, the goal of this technology is to achieve faster response to yaw and lateral forces and reduce pitch and the propensity for body roll. And even though a vehicle’s steering ratio remains unchanged, the hardware also can result in faster steering response.

Pro driver Tetsuya Yamano shows journalists the lines at Suzuka Circuit.

Likewise, an automatic transmission controller can be tweaked for closer gear ratios to get the driver more quickly to the meat of the engine’s powerband.

All of these enhancements become plain as day during test drives of identical vehicles with and without the technology at Japan’s famous race track here, the Suzuka Circuit, home to many race series, including Formula One.

Right-hand-drive test vehicles include unaltered factory editions of the BRZ coupe and Forester CUV, as well as the tS variants evaluated back to back.

Modified Versions Great Fun at Track

The standard BRZ handles reasonably well. But the modified tS version, with the same 2.0L naturally aspirated 4-cyl. boxer and the additional chassis and suspension hardware, feels like a different car, capable of carrying a lot more speed into a corner with greater stability.

Same for the Forester, a 5-passenger ute that almost never will be driven this aggressively with its 2.0L turbocharged boxer-4. But it’s good to know you can, with a fair degree of confidence, in the tS model.

Of course, the WRX STI is at the track, and there are three versions for thrashing. The first two are the previous generation (S206) with additional tS suspension bits and the latest model, all stock, which launched last year. Each model uses the same 2.5L turbo-4 rated at 305 hp.

The star of the event, until it is sidelined with a wonky clutch, is a prototype WRX STI with a 2.0L turbocharged boxer-4, an all-new chassis, bigger brakes, wider tires and stiffer coil springs, while using production dampers.

Subaru says the prototype is 40% stiffer than the current WRX STI, which is readily apparent on the track, and the car understeers less. In addition, front suspension components are inverted to further resist lateral forces.

Most remarkable is how much more enjoyable all the modified vehicles are to drive with the addition of certain suspension and chassis hardware. Test drives are limited to the track, but the improvements clearly would be appreciated on public roads as well.

With a focus on ride and handling, Hirakawa says there is no plan to increase horsepower or torque ratings in STI-badged vehicles. Once the expanded STI business plan takes root sometime in the future, he says the automaker will consider boosting engine output.

More immediately, Subaru is focusing on making some of these STI parts available online and through dealers.

Aftermarket performance parts that had been branded Subaru Performance Tuning (such as strut braces and cold-air intakes) soon will carry the STI name.

Mirror shows flexible draw stiffeners installed on BRZ STI test car.

After years as an interesting offshoot, the STI division now is strategically integrated within Subaru’s long-term business plan, known as Prominence 2020.

Once the aftermarket parts start generating more revenue, the vision is to offer complete vehicles “tuned by STI” with modifications to the exterior, interior and, of course, chassis and suspension.

For Hirakawa, that day can’t come soon enough in the STI gameplan. “The complete car is our first priority in the U.S.,” he says.

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