Debuting at the 2019 North American International Auto Show in Detroit, the STI S209 is a new S-line performance model to be sold in limited numbers in the US in order to qualify as a racing machine in competition. The S209 embodies the aggressive performance of STI's new S-line.
Subaru Tecnica International (STI) is the performance arm of Subaru, best known to consumers through the WRX STI models sold as street-legal rally cars. This S209 is the first STI-exclusive design that's being sold directly to the public, and is, literally, a street-legal race car and will be offered in a limited run of just 200 units.
The S209 is based heavily on the STI-designed WRX STI Nurburgring Challenge race car, which won the SP3T class in 2008 as the fifth win for Subaru at the 24 Hours of Nurburgring.
It carries a very similar wide-body exterior treatment, making it 1.7 inches (4.3 cm) wider than a production WRX STI. These bulging fenders accommodate a wider track and bigger tires. The track of the S209 is 0.6 inches (1.5 cm) wider than a production WRX STI. The S209 will include Dunlop SP Sport Maxx GT600A summer tires and lightweight 19 x 9-inch forged BBS alloy wheels. Dunlop developed the tires specifically for the S209.
The wider fenders also serve to allow more venting to the engine for cooling and more air turbulence control via vents at the rear of the car. The larger wheels allow more aggressive Brembo brakes with cross-drilled steel rotors and 6-piston monoblock calipers (front, 2-piston at rear).
Powering the STI S209 is a reworked version of the EJ25 2.5-liter turbocharged four-cylinder opposed-piston ("Boxer") engine that's propelled Subaru vehicles for a long time. It's been given STI treatments, including a new HKS turbo, to output 341 horsepower (254 kW).
A larger turbine and compressor, both about 6 and 8 percent bigger than the WRX STI, helped boost that power output. Maximum boost pressure for the S209 is now 18 psi, about 1.8 psi more than in the WRX STI production model. The Boxer engine also receives forged pistons and connecting rods that are lighter in weight and stronger. Torque is improved by 10 percent in the midrange (3,600 rpm) for higher speeds on corner exits.
Airflow to the engine is of extreme importance in the S209 and STI added a high-flow intake system. This system has a new intake duct, induction box with conical air filter, and silicone turbo inlet duct, as well as an intercooler water spray system for temperature control. The latter is manually operated through steering wheel paddles.
The S209 also has more aggressive fuel delivery with a high-flow fuel pump, larger fuel injectors, and a newly-tuned engine control module. On the exit end of the system, high-performance mufflers reduce airflow resistance by 17 percent and hand-polished stainless exhaust tips add acoustics.
That re-tuned 2.5 L engine is attached to a close-ratio six-speed manual transmission and Subaru's legendary Symmetrical All-Wheel Drive with front/rear limited-slip differentials. The Driver Controlled Center Differential from the WRX STI is still present in the S209, of course, and torque vectoring and vehicle dynamics control are also there.
STI recalibrated the S209's SI-Drive to accommodate the familiar three-mode operation from the WRX STI for better everyday comfort. The Intelligent mode improves fuel economy and offers smoother power delivery for daily driving, Sport mode for more response while retaining throttle control, and Sport Sharp for best acceleration times. Sport Sharp is best for fast acceleration in short bursts while Sport is best for track running where maneuvers are also important.
On the bodywork of the STI S209 are several indicators, outside of the wider body and changed aerodynamics, which indicate this is no standard WRX STI. Subaru badges have been replaced with STI all around. Two body colors, World Rally Blue Pearl with gray wheels and Crystal White Pearl with gold wheels, will be available. S209 badges are affixed to the front grille, fenders, and rear deck lid.
STI will announce pricing for the S209 closer to its expected launch date in late 2019.
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