Subaru chose the 2019 North American International Auto Show to reveal the most powerful WRX STI ever offered in the United States. The new WRX STI S209 is powered by a 2.5 litre turbocharged 4 cylinder boxer engine that generates 341 hp, a 10 percent increase over the WRX STI’s 310 hp. This marks the first time that Subaru is offering an S-line STI in the United States. Only 200 of the S209’s will be available all of which will be in either World Rally Blue Pearl or Crystal White Pearl.

The WRX STI S209 encompasses upgrades in power, handling, aerodynamics and driver engagement. Final assembly takes place in Kiryu, Japan, where it receives engine modifications and bodywork alterations that in total require it to be homologated for the U.S. by STI. The S209 is considered the first “STI-built” Subaru sold in the United States. the previous S-line STIs, the 2000 S201 through the 2018 S208, were only available in the Japanese domestic market.

Designed with a focus on high-performance driving, the S209 draws inspiration and tech transfer from STI’s most formidable track machine, the WRX STI Nürburgring Challenge race car, which won the SP3T class at the 2018 24 Hours of Nürburgring. The S209, like the Nürburgring Challenge race car, has an expanded wide-body exterior treatment, which extends the cars 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 performance tires fitted to lightweight 19 x 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 maximum lateral grip of over 1.0 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 6-piston monoblock front calipers and 2-piston monoblock rear calipers, provide greater braking capability thanks in part to upgraded high-friction pads that deliver improved fade-resistance.

The S209 has 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, like the Nürburgring race car, 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. Other Nürburgring race car tech that trickled down to the S209 include front, rear and side under spoilers; front bumper canards; and carbon-fiber roof panel and rear wing.

The S209 has a thoroughly reworked version of the EJ25 2.5-liter turbocharged 4 cylinder boxer engine. Featuring an HKS turbocharger, the EJ25 engine delivers 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 18.0 psi (16.2 psi for WRX STI). The enhanced engine utilizes forged pistons and connecting rods that are both lighter and stronger. Midrange torque gets a notable bump, up 10 percent at 3,600 rpm, delivering higher corner exit speeds when driving on the track.

The S209 is only available with a close-ratio 6-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.

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.

The S209 receives multiple tweaks to elevate it from other STI sedans. An STI badge replaces the traditional Subaru star cluster on the center of the D-shape steering wheel, which is wrapped in Ultrasuede with silver stitching, a treatment that carries over to the lid of the center console storage box. An S209 serial number badge resides on the center console, and S209 badges adorn the passenger-side dash and the headrests of the Recaro® front bucket seats, which feature new silver-hued inserts. Outside, special S209 badges are affixed to the front grille and fenders as well as the rear decklid.