Pre Event (2015)

ADAC Qualifying Race 24h
SUBARU WRX STI faces setbacks

The ADAC Qualifying Race 24h took place on Sunday 12 April at Nürburgring in Germany and ,STI, with drivers Carlo van Dam, Kota Sasaki and Hideki Yamauchi entered with the SUBARU WRX STI Nürburgring Challenge car. The Subaru started from the top of the class as a result of the qualifier, but right after the driver change from van Dam to Sasaki, the car sustained damage after colliding with another car, which forced the team to retire from the race.

Unexpected pitfalls challenge the team

The WRX STI Nürburgring car was transported by air to Germany at the end of March, and after preparation for participation, it took part in the official event schedule of the ADAC Qualifying Race 24h on 10 April. The team entered the event this time with 3 drivers: van Dam and Sasaki, who both have experience in the 24-hour race, leading the team, as well as Yamauchi, a new hire for the Subaru team in SUPER GT, who needed to gain experience for the coming 24-hour race. The team had a plan to collect data on car setups and tyres for their main purpose of participation in this event. However, as the free practice got under way on Friday, problems with the newly introduced paddle shift hit them preventing them from running more laps as they had wished. They figured out that the gear itself seemed to have a problem and decided to replace the whole assembly of the transmission before the qualifier on Saturday. The replacement work took a long time and this single task already put a heavy burden on the mechanics and engineers. “We have introduced bold improvements to win this year, but as usual, new attempts don’t always work so smoothly”, said STI General Team Manager Hideharu Tatsumi. “Not just with the gear box, but some more issues with other areas occurred, and with those problems combined, our chance to run the car slipped away. In addition, the track conditions changed from wet to dry due to the changeable weather. So we couldn’t get the chance to run the car enough before the two qualifiers”.

While heavy damage was incurred,
there is some promise

There was another qualifier in the morning of the 12th with van Dam recording the team’s best time since the start of this event. Thanks to that, they became eligible to start the 4-hour race from the top of the SP3T class. Meanwhile, newcomer Yamauchi had the chance to drive just 3 laps, setting a good rhythm during the qualifier, so it was also beneficial for the team.Yamauchi said that even with just 3 laps, he was able to understand the layout of Nordschleife well, and it was a good experience. After that, the race started in a dry condition at noon with van Dam behind the wheel of the SUBARU WRX STI Nürburgring car. After completing normal laps, van Dam came back to the pit and passed the car over to Sasaki. Normally in a test, he would have driven routine laps to check areas such as tyre wear, but on his 3rd lap, an unexpected accident happened when the WRX STI contacted another car while running side-by-side with it.

By ill fortune, tyres on each car hit each other, which caused the WRX STI to leap and then land askew. Sasaki managed to come back to the pit, but damages extended into the bumper, the under-floor parts, the suspension and a part of the body. As a result, the team had to give up continuing the race. Tatsumi said, “Damage spread across a wide area, and we could not continue the race. It was also disappointing that we could not complete many of the tests we had planned. However, even with some concerns remaining with the paddle shift at that time in the qualifier, Carlo (van Dam) recorded the best time of 9 minute 10 seconds to take pole position. This has reminded us that our long-sought goal to break the 9-minute barrier as a lap time is not a tall order, and it sounds promising. Now we are going to fix the car and concentrate on running it without any restraint to display its full ability”.

SUBARU WRX STI Nürburgring Challenge 2015
undergoes a shakedown test at Fuji Speedway

Subaru Tecnica International (STI) ran a shakedown test of the SUBARU WRX STI Nürburgring Challenge 2015 car, which will be run this May in this year's Nürburgring 24-Hour Race in Germany, at Fuji Speedway on Wednesday 4 March.

This car has been under development since last summer and undergone repeated running experiments on the SUBARU test course in Tochigi, Japan, but this was the first time for STI to demonstrate the car on a circuit in front of the media and partners. After an hour of driving, an excited Kota Sasaki, who will participate in the 24-hour race for the fifth time this year, said. “I felt that the longitudinal rigidity of the chassis has been further improved compared with the last year's car, and the interlocking property of the front and rear wheels has been enhanced. Further, the nose turns in even more quickly, and so, I thought that it would be easier for us to take advantage of the distinctive characteristics of an AWD when we drive it at Nürburgring. The paddle shift system has been introduced for the first time and still gives some strong gearshift shock. Therefore, further adjustment will be required, but this will also be effective in improving our times. Regarding aerodynamics, I feel that the down force at the front is very effective. I can't wait to drive it at Nürburgring ”. He added, “I will be the only Japanese driver to drive this car in the race this year. As I carry the hope of the Japanese SUBARU fans, it makes me nervous but at the same time, I feel it's very rewarding. I am grateful to be given this opportunity.”

As he explained about their Nürburgring programme, Yoshio Hirakawa, President of STI said, “We felt the sting of defeat last year, so we are really hoping to get a win back in the SP3T class this year. Therefore, we started this project last July soon after coming back from the race, and since then, I have been urging the development team to build a race-winning car with bold thinking. If you look inside the engine room, I believe that you'll notice a large difference from last year's car. Even this one aspect should raise expectations”. Team Manager Masahiro Ozawa echoed his president saying, “Our advantages have been reliability and durability. We have also been working to incorporate performance which is as good as our rivals' in the 2015 model. I know that our rivals have also improved and they will be strong. Our whole team will work together to compete against them”.

General Team Manager Hideharu Tatsumi who has led the development of the car said, “Since we won the SP3T class in 2012, we have been missing the tenacity and vigor for a win. This year, we have thoroughly analyzed last year's results and reviewed each area of the car. In doing so, we have revised the layout of the engine auxiliary machines and introduced the paddle shift system. However, the major change has been the improvement in stiffening the chassis and aerodynamic performance. Moving the steering wheel to the left hand side has also contributed not only to securing drivers' view on the clock-wise circuit, but also their visibility for flags waived at posts and the efficiency of pit work. Concentrating SUBARU's technology used in its mass-production cars and STI's tuning technology acquired through its complete car development, we have utilized our comprehensive strength in the development of this racecar. Also, from that perspective, we must take a win back home this year”.

The Nürburgring Challenge car will be fine-tuned and checked on a test course before being transported to Germany in mid-March. The team will then participate in the Qualifying Race 24h Nürburgring in the second week. Following that, at the end of April, they will also compete in a VNL race. They will finalize settings for the Nürburgring circuit using these two occasions before the race week of the 24-hour race in the third week of May.

STI conducts wind tunnel tests with the
Nürburgring Challenge 2015 car

STI tested its SUBARU WRX STI Nürburgring Challenge 2015 car, which will be competing in this year's Nürburgring 24-Hour Race, at the wind tunnel test facility at Fuji Heavy Industries' Gunma factory in Ota City, Japan, on 21 February.

This facility is equipped with a state-of-the-art wind tunnel, allowing the data acquisition of aerodynamic performance of each area of a vehicle while under running conditions on a moving belt system. STI utilizes this facility for racecar development. In fact, decisions on such areas as the final shape of aerodynamic devices on past Nürburgring and SUPER GT racecars were made based on the results of aerodynamic performance analysis tests done here.

After being unveiled at Tokyo Auto Salon, the Nürburgring 2015 car went to Ota for collection of basic data and as a result, various modifications were made to the car. After this test, the final specifications of the car will be determined before it goes through a shakedown prior to transportation to Germany.

In a manner of speaking, STI has put forward two contradicting objectives for the specifications of this year's Nürburgring Challenge car to challenge last year's defeat. The car needs a setup which gives necessary down force on the winding track of the Nordschleife -North Loop. At the same time, it requires an aero dynamic setup which can minimize air resistance on the long straight through to the first corner on the Grand Prix track in the last half of the lap. To achieve this, there are various difficulties to overcome. In order to get as much down force as possible, the mounting position of the rear wing should be moved to the cutting edge permitted by regulations as down force is generated when the CLr value becomes negative, and accordingly, lift (CLf) created by devices such as a front under spoiler and canards -additional aerodynamic parts at the top of the front fender, should be adjustable. The shapes of the front and rear fenders should also be designed to allow the reduction of resistance of air flowing to the sides of the car body. Air resistance needs to also be reduced by the efficient discharge of air going through the engine compartment while airflow must contribute to the cooling of the inside of the compartment as well.

Regarding these challenges, the data of a wide variety of conditions and designed shapes of additional parts are input into an industrial computer using a Computational Fluid Dynamics (CFD) analysis tool to figure out the near ideal shapes before such a wind tunnel test. This tool enables the analysis of not only the aerodynamic performance of different areas but also the aerodynamic balance of the entire vehicle. Fully utilizing these capabilities, designed aerodynamic devices are developed and then the actual car is tested in a wind tunnel with such devices installed. However, the performance data measured at this stage is not versatile and detailed settings cannot be finalized until the car is actually run. In fact the test day began early morning to measure aerodynamic performance of combinations of various devices. It is very sensitive and demanding work to determine ideal shapes while dealing with air -an invisible element. As it is actually the people who leverage a CFD analysis tool and verify ideal shapes during the wind tunnel test in order to accommodate them into the final car. This means that engineers who work on such tests require abundant experience and good sense.

Having gone through this type of verification, the body shape of this year's Nürburgring car is now different from last year's. It will be exciting to see the end of this year's race to know how much faster the car has become as a result of these changes, and how these have contributed to fuel efficiency.

※this information is as of 2015.