Subaru to Offer Track-Hungry STI S209
Subaru Tecnica International (STI), a Subaru subsidiary, has introduced the limited-edition STI S209, the first-ever S-line STI product produced exclusively for the U.S. market.
As an S-line product, the STI S209 encompasses upgrades in power, handling, aerodynamics and driver engagement. It undergoes final assembly in Kiryu, Japan, where it receives engine modifications and bodywork alterations for the U.S. market.
The S209, designed with a focus on high-performance driving, draws inspiration and tech transfer from STI’s most formidable track machine: the WRX STI Nürburgring Challenge racecar, which won the SP3T class at the 2018 24 Hours of Nürburgring. It marked the fifth time STI dominated the SP3T class at the grueling endurance race, according to Subaru.
The S209-like the Nüburgring Challenge racecar-wears an expanded wide-body exterior treatment, which extends the vehicle’s overall width to 72.4 inches, or 1.7 inches wider than a standard WRX STI. The bulging fenders accommodate wider front/rear tracks (+0.6 in front/rear) and 265/35 Dunlop SP Sport Maxx GT600A summer-only tires wrapped around lightweight 19-by-9-inch forged BBS alloy wheels. The all-new tires, developed exclusively for the S209 by Dunlop, are a significant contributor to the car’s tenacious maximum lateral grip of over 1 g. Vents on the front fenders provide additional engine cooling, while vents on the rear fenders rectify air turbulence to reduce drag. Brembo brakes, with cross-drilled steel rotors and six-piston monoblock front calipers and two-piston monoblock rear calipers, provide stout stopping force, thanks in part to upgraded high-friction pads that deliver improved fade-resistance.
Underneath the S209’s broader body are specially developed Bilstein dampers, stiffened coil springs, a 20mm rear stabilizer bar and pillow-type bushings for the front/rear lateral links. The S209 incorporates reinforcements to the front crossmember and rear subframes and, a la the Nürburgring racecar, a flexible front-strut tower bar and flexible front/rear draw stiffeners.
The flexible tower bar, unlike a conventional rigid bar, is split and joined with a pillow ball joint in the center to be longitudinally mobile while helping laterally stiffen the body of the car. The result is optimum tire grip during lateral moments combined with compliant ride during longitudinal moments, according to Subaru.
Meanwhile, the draw stiffeners apply tension between the body and cross member to optimize chassis flex, improving stability when cornering and delivering better ride, handling and steering response, according to the company. Other Nürburgring racecar tech that trickles down to the S209: front, rear and side under spoilers; front bumper canards; and carbon-fiber roof panel and rear wing.
Fighter on Track, BOXER Under Hood
A thoroughly reworked version of the EJ25 2.5-liter turbocharged BOXER engine propels the S209. Featuring an STI turbocharger manufactured by HKS, the EJ25 serves up an estimated 341 horsepower, thanks in part to a larger turbine and compressor (up 6 and 8 percent, respectively, compared to WRX STI) as well as maximum boost pressure that has been increased to 18 psi (16.2 psi for WRX STI), according to Suburu.
The enhanced BOXER engine utilizes forged pistons and connecting rods that are both lighter and stronger. Midrange torque, too, gets a notable bump, up 10 percent at 3,600 rpm, delivering higher corner exit speeds when driving on track.
For ultimate driver engagement, the S209 comes exclusively with a close-ratio six-speed manual transmission that routes power to a full-time Subaru Symmetrical All-Wheel Drive system with front/rear limited-slip differentials, a Driver Controlled Center Differential (DCCD), Active Torque Vectoring and Multi-Mode Vehicle Dynamics Control. A recalibrated SI-Drive system offers three modes: Intelligent (I) for improved fuel economy and smoother power control; Sport (S) for optimized power balance between response and control; and Sport Sharp (S#) for achieving the best acceleration times.
STI engineers recommend Sport over Sport Sharp for circuit driving, as the less aggressive throttle map allows for greater driver control.
Air & Fuel
To feed more air to the EJ25, the S209 uses a high-flow intake system featuring a new intake duct, induction box with conical air filter, silicone turbo inlet duct and, a nod from the 2004-07 WRX STI, an intercooler water spray system that lowers intercooler temperature via manually operated steering-wheel paddles.
More air demands more fuel, so the S209 receives a new high-flow fuel pump, larger fuel injectors and an STI-tuned engine control module.
High-performance mufflers deliver 17-percent less airflow resistance while larger hand-polished stainless-steel exhaust tips-101mm in diameter-deliver aggressive appearance and acoustics, according to Subaru.
Around 200 units of the STI S209 will be built, earmarked exclusively for the U.S. Available exterior color/BBS wheel combinations will be WR Blue Pearl/gray wheels and Crystal White Pearl/gold wheels.
Pricing will be announced closer to the on-sale date in late 2019.