the presence of Subaru at this year's Detroit Motor Show has a curious feature. The big star of the brand in the North American salon, despite looking like a Subaru WRX STI, goes by the name STI S209 and is the first model in Subaru's “S-Line” series to be sold outside Japan, with 200 units destined for the North American market.
The reason the Subaru WRX STI changed its name in this hardcore version is simple. The work done by STI (Subaru Tecnica Internacional) to create the S209 was so profound that the brand decided to homologate it in the United States as STI instead of Subaru.
Compared to the Subaru WRX STI on which it is based, the STI S209 is wider (43.2 mm) and has a wider lane width (15.2 mm more). It also changed to 19″ wheels from BBS and received shock absorbers from Bilstein, stiffer springs and a 20 mm stabilizer bar at the rear. The braking was done by Brembo brakes (with six pistons in the front discs and two in the rear ones).
The engine of the STI S209
The STI S209's biggest point of interest is the engine. An evolution of the EJ25, originally released in 1996, this 2.5 l boxer turbo received several improvements that made it start to charge around 345 hp (there are still no official data). These numbers make it one of the most powerful Subaru (sorry STI) ever, second only to the Cosworth Impreza STi CS400 which had… 400 hp and of which only 75 units were produced.
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To achieve a power increase of around 45 hp (in the WRX STI this engine produces around 300 hp) STI replaced the original turbo with HKS with a larger turbine and compressor that allows a maximum boost of 18 psi instead of the original 16.2 psi.
In addition, the engine also received forged pistons, wider injectors and… water injection — not in the combustion chamber, as in the BMW M4, but over the intercooler, to manually lower the temperature via the lever on the steering wheel.
Associated with this engine comes a… six-speed manual gearbox and to transfer power to the asphalt, the STI S209 has, as expected, an all-wheel drive system.