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The Versatile WRX STI

Preparation

 

Road Racing Car

 

Subaru of America road racing partner Phoenix Performance built its #35 WRX STI race car to compete in the Grand Sport (GS) Class of the GRAND-AM Continental Tire Sports Car Challenge. Phoenix Performance campaigns the car in 2010 as the Subaru Road Racing Team (SRRT).

 

Work on the car began more than a year ago. This WRX STI was factory stock when Phoenix Performance took delivery.

 

The first stop was the company's dynamometer to establish a baseline for power development.

 

The car was then completely disassembled to begin the race-prep process, including removal of seam sealer and caulking. Body seams were welded for added strength. Phoenix Performance also custom-fabricated the roll cage.

 

The body was sand-prepped for a complete paint process, including primer, sealer, basecoat, and clearcoat. The process from dismantling through paint took approximately three weeks.

 

Then the #35 was reassembled. The driveline, which remained mostly stock, was reinstalled. The SUBARU BOXER engine, Subaru Symmetrical All-Wheel Drive, Driver Controlled Center Differential, and Subaru Intelligent Drive all remained intact.

 

Additional safety equipment was added, including a safety fuel cell, window nets, and onboard fire suppression system, as well as a racing seat and safety harness.

 

Race-specific chassis and suspension equipment were installed as allowed by GRAND-AM, including KONI shock absorbers, heavy-duty suspension bushings, thicker sway bars, upgraded 4-piston Brembo®1 brakes (chosen because they accommodated thicker brake pads), and wider wheels and tires.

 

Phoenix Performance fabricated the heavy-duty radiator with oil cooler, the transmission cooler, and the differential cooler.

 

The Engine Control Module remained stock, although it was tuned for higher performance, as was the anti-lock braking system. The traction control and stability control systems were shut off for competition.

 

By GRAND-AM rules, minimal weight for the car (without fuel) can be reduced to 3,100 pounds.

 

The engine remained stock. GRAND-AM allows greater boost pressure, though, by approximately 2 psi.

 

Rally Car

 

 

Photos: Lars Gange | rally.subaru.com

 

Subaru Rally Team USA (SRT USA) #199 -- fielded by Vermont SportsCar and driven by Travis Pastrana -- was built in a similar way. Vermont SportsCar began with a stock WRX STI. The body was stripped, lightened, and seam-welded. Then a roll cage was installed.

 

Just as on the road racing car, a safety fuel cell, racing seat, safety harnesses, and fire suppression system were added. The interior also received a custom WRX STI dashboard, carbon-fiber door panels, and rally odometer.

 

The stock 2.5-liter SUBARU BOXER engine was replaced by a 2.0-liter unit -- turbocharged and intercooled, although limited by a 34 mm turbo inlet restrictor. The engine powers #199 through a 5-speed, close-ratio, dog-engagement transmission, which allows shifting without depressing the clutch. Other performance items included launch control, turbo anti-lag system, hydraulic hand brake, and competition electronic control unit for the Driver Controlled Center Differential. The chassis was upgraded with competition rally shocks.

 

The exterior reveals several modifications, including mud flaps, 1/4-inch skid plate, roof-mounted air scoop, and vertically slotted wing. #199 weighs in at less than 3,000 pounds.

 


Photo: Garth Milan/
Red Bull Photofiles

Record-Attempting Jump Car

 

Pastrana's "Red Bull: New Year. No Limits." jump WRX STI started as an SRT USA Open Class rally car. It retains modifications made for rally as in the #199, with the exception of the 2.5-liter SUBARU BOXER engine under the hood. That's been tweaked to approximately 400 horsepower and 451 lb-ft of torque.

 

1 Brembo is a registered trademark of Freni Brembo S.p.A.

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