Feature: Subaru WRX STI NBR 24-Hour Challenge 2014 Race Car
Nürburgring Photos Courtesy Subaru
Home of the 24 Hours of Nürburgring, the legendary Nordschleife is renowned for its terrifying and punishing route through the Eifel mountain range in the west of Germany near the Belgian border. Considered one of the most demanding road circuits in the world, the Nordschleife winds its way through narrow mountainous terrain filled with tight hairpin corners and blind crests. It’s the ultimate test of both driver and machinery that can and has humbled even the most experienced race car drivers.
The inaugural race at the ‘Ring took place on June 18, 1927; today the track layout remains the same – it’s a throwback to a simpler era, and has remained unaffected by the passage of time. The best-known event today is the ADAC Zurich 24-hour race, which combines the Nürburgring’s two circuits – the Nordschleife and the Grand Prix layout. Over the course of four days, the entire circuit is transformed into a 15 mile-per-lap event – the course presents drivers with 300 meters of elevation change and 170 corners which vary from tight hairpins to high speed sweepers. Every year, the 24 Hours of Nürburgring brings over 200 race cars; gasoline, diesel-powered, natural gas, and even hybrid electric vehicles from around the world try to conquer the “Grüne Hölle” or “Green Hell”.
Among the 2014 ADAC Zurich 24-Hour Race competition stood this race-prepped 2014 Subaru WRX STI, designed to run in the SP3T class. This class is categorized for turbocharged engines displacing 1.75 to 2.0-liters. The Subaru, based on the 2015 WRX STI chassis, races in this class against competitors from Audi and Volkswagen.
Fuji Heavy Industries (FHI), the manufacturer of Subaru, and Subaru Tecnica International (STI), the company’s motorsports arm, collaborated their development efforts to design a race car. The end goal was to secure a third victory in the SP3T class after finishing second place the previous year. This was the seventh consecutive year that Subaru has participated in the race with the WRX STI.
We were fortunate enough to catch the Subaru’s shakedown session at Mazda Raceway Laguna Seca a few weeks prior to Subaru shipping the car overseas to the Nürburgring for more fine-tuning and performance adjustments before the big race. The drivers and crew members worked tirelessly around the clock in preparation for the grueling event as I captured the action; they also granted us access to secure close-up photos of the inner and outer workings of this meticulously-built machine.
Preparing a car to compete in this grueling 24-hour race is the ultimate engineering test. Every element of the STI racecar was carefully conceived, then tested to ensure the components would survive the immense pressures and g-force loads seen when participating in the race at high speed over 24 hours.
Over the years, Subaru Tecnica International has used the Nürburgring as their proving ground and symbolic place of worship for testing their products. Central to this is the belief that if a vehicle and its various components can survive the challenge of the Nürburgring, they can handle anything the company’s retail customers might put them through. The idea of taking a mass-produced vehicle and transforming it into a purpose-built race car designed to push the outer limits was a challenge that the team was more than ready to accept, and the end result was a STI race car which used 95-percent of the production car’s parts.
STI-engineered air jacks quickly lift the Subaru off the ground as a means of servicing the wheels and tires in the pits. As it’s equipped with a set of custom re-valved Bilstein adjustable race coilovers on all four corners alongside STI suspension components, the Subaru’s lowered stance ensures uncompromising handling regardless of track conditions. Every suspension component was adjusted, then marked by their chassis engineers for reference when it came time to look over track data and make adjustments for better performance.
A set of BBS CH-R 18×10 wheels wrapped in Dunlop 18-inch race compound tires are on all four corners, and factory STI strut braces along with a STI prototype front strut bar increase the strength of the already-rigid Subaru chassis. Aiding the driver’s control are custom-spec front and rear limited slip differentials to provide added traction and efficient power transfer through all four wheels. In this application, a rear differential cooler was implemented to ensure temperatures were kept in check.
A sequential 6-speed transmission is used to provide ultra-smooth shifting capability, while the factory brakes were upgraded to Brembo Monobloc 6-piston front and 4-piston rear brake calipers, then outfitted with slotted rotors. Upon close inspection of the brakes, it’s evident that multiple hairline cracks on the face of the rotor show us the extreme temperatures the brakes witness during competition. Those glowing rotors you see on TV aren’t just special effects – they’re the real deal!
One feature that caught our attention was the use of polycarbonate side and rear windows that were designed and manufactured in-house by Subaru Tecnica International. We can imagine this was done in order to maintain quality control while keeping production costs down.
A set of Craft Square side view mirrors were painted in traditional Subaru Sakura pink and secured in place using a metal support bracket to ensure they don’t shift when the Subaru runs the speedometer north of 150 mph on the Nürburgring’s straights.
Crack open the dry carbon composite doors and you’re in for a motorsports enthusiast’s treat. A Subaru Tecnica International-built roll cage has been welded onto modified points within the subframe. These cages are inspected and marked for approval before every race – they must be built to sanctioning-body standards. A Recaro Carbon Kevlar RAO bucket seat combines with a set of MPH-340 Takata Harnesses ensure all three drivers are securely fastened within the confines of the vehicle at high speeds. Mounted in place of the factory rear seat is an 18 gallon fuel cell that has been ducted to keep the fuel as close to ambient temperature as possible. Motorsports grade mil-spec wiring and an STI-programmed Motec ECU maintains proper fuel and spark delivery to the engine.
The center-console switches and the dials located on the steering wheel allow the driver to dial in the handling while blasting down the tarmac. Perhaps the most intriguing item on this STI sits at eye level with the driver. Sitting to the left of the dash display was an Orient shock-resistant mechanical “M-FORCE” watch. We are not sure if its sole purpose was strictly as a promotional item for their sponsors, but the case can be argued that drivers in a 24 hour event needs to keep track of time. Positioned in the original gauge cluster is a Motec display. The Motec cluster offers digital monitoring of the engine vitals, including the ever-important lap time readout for circuit racing competition.
Under the Hood
The 2.0-liter engine was modified to produce 340 horsepower and 340 lb-ft of torque. Interestingly enough, the intake manifold, turbo, and top-mount intercooler all appear to be parts that can be purchased from your local dealership. While the power numbers aren’t anything to write home about, it’s important to note these numbers were limited due to the class requiring a 38mm restrictor. The 2.0-liter in the Japan only model produces 304 hp and 311 lb-ft of torque. Keep in mind this is a 24 hour race and the car that makes it to the checkered flag takes home the trophy. A Subaru making over 700 horsepower would be ideal, but the additional stress caused by the larger horsepower output would reduce the vehicle’s overall reliability.
A month following our photo shoot, the WRX STI entered the 24-hour race and finished fourth in the SP3T class and 32nd overall. Coming in fourth place would be considered a noteworthy accomplishment for any race team, but for the drivers and Team Subaru, it wasn’t what they set out to accomplish. Luck wasn’t with the team at the 2014 event as a series of accidents and caution flags slowed the event down to a snail’s pace. The STI was caught in an accident at the 4:45 mark and was forced into a pit stop afterward, due to a flat front right tire. The pace quickly picked up for the team, but they were once again hit with a curveball as the STI experienced drivetrain problems at 8:40.The team quickly went into action to replace the transmission and bring the car back onto the track. Adding insult to injury, the car and driver received a drive-through penalty that proved costly, as it allowed their competitive SP3T class adversaries to sneak by and capture the podium.
The team bounced back the following year at the 2015 Nürburgring 24-Hour race with a new class win for the third time following its victories in the 2011 and 2012 races. This year’s ADAC Zurich 24-Hour Race took place just on May 26 to 29th under heavy rain and hail weather conditions but Subaru Tecnica International prevailed once again as they dominated and took the SP3T class win after completing 121 laps. This year’s event marked STI’s competition in the Nürburgring 24-Hour Race for 9 consecutive years. Congratulations to the drivers and team members; we look forward to seeing next year’s race car as they compete for another podium finish!