2018 Advanced technology of STI to explore from race car vol.3
In addition to the domestic Super GT 300, the Subaru STI’s race has a 24-hour endurance race to be held in Nürburgring, Germany. SUBARU WRX STI NBR Challenge 2018 participating vehicles are based on WRX STI on the market and are adapted for racing such as safety standards and weight reduction. In 2017 I retired with contact other cars and accidents like doubting the eyes of fire, what kind of battle will it be in 2018 ? I asked Mr. Hideharu Tatsumi of the team director.
ーーTatsumi
I think that there are many causes of fire, but what matters is not to repeat the same thing, including installing injectors, but I will work more carefully than before, but in a situation that can not be predicted in the race So, if you stop the engine, stop the fuel if it detects zero speed, I stopped it in 2 seconds, but I changed it to stop in half a second.
Although it is certainly necessary to take countermeasures against accidents, it is necessary to take measures in the regulation including the determined vehicle weight. Well, in 2018, I asked specifically what kind of change and challenge each part such as the engine, body etc of the machine.
ーーTatsumi
As for the engine, the air restrictor is 37 φ as same as last year, so it has dropped by 15 ps or more, so it is basic idea how to put out the time in a place without power
Since WRX STI to participate in 2015 and 16 years has won the class for two consecutive years, the size of the restrictor has been restricted from 38 φ to 37 φ since 17 years since it won the class. The displacement of the SP3T class is 2.0L turbo car, but the drive system is not limited, but the restrictor diameter is different.
Also, WRX STI participating in AWD has a vehicle weight of 1220 kg, but 2 wheel drive vehicle is both FF and FR, 50 kg lighter 1170 kg. However, rival Audi TT RS 2, Lexus RC is 1250 kg, and has participated in 39 φ with a large restrictor diameter. In addition, compared with WRX STI, it is participating in the condition of +1 inch in tire width and +10 litters of fuel tank.
If the size of the air restrictor is large the power can be given, “My top speed doesn’t come out, about 240 km / h, about 252、3 km / h on the down slope, or so. Audi and Lexus are more speed “The difference between the air restrictor and the like is such that the power difference, the difference in the top speed comes out as it is.
However, even if we can generate power, if there is weight of the car, the brakes will become more severe and the fuel consumption will also drop, so making vehicles is difficult if we take that into account. However, in the background of Subaru’s entry into the races, there is also an idea to use technology used for mass product vehicles in races, and there is no option to abandon AWD. Of course the engine to be mounted does not even think of participating in a pure race engine.
The rival Audi TT RS is equipped with a 2.5-liter 5-cylinder engine, but for a 24-hour Nürburgring race, the output is 360 ps with a 2.0-liter five-cylinder engine with a short stroke and reduced displacement. The class is SP 3 T, FF 2 WD. This mounted engine is a motor sports engine developed exclusively for Audi Sports, which is a derivative engine of the V10 type engine based on racing.
Meanwhile, the EJ 20 type that WRX-STI is equipped is an engine which has been 29 years since its debut and has sufficient results and reliability, but at the highest output it is painful against rivals.
Given these vehicle circumstances, the task of director Tatsumi “how do you put the time out in the absence of power?” Is heavy.
ーーTatsumi
Turbo adopts an anti-rag (misfiring system) and changes it to improve the power of the power from the partial, so we are looking for a good turbine, so we are looking for a good one I think that the speed at the corner will be better than before, and I think that a shortage of power will be compensated even a little, but on the other hand, if you turn it into an anti-lag, the problem of heat comes up, and the work that is doing now will crush one by one It’s work.
The anti-lag is a technology that intentionally burns misfire at the exhaust manifold part. When the accelerator is off, the exhaust turbine slows down and decelerates, and the air sent to the compressor also goes out. As a result, a turbo lag occurs when re-accelerating, but it ignites the inside of the cylinder, burns the fuel in the exhaust manifold and does not degrade the rotation of the turbine with the flow of the high temperature exhaust gas.
ーーTatsumi
In a mass products car, we are using castings and there is no problem with heat resistance, but there are many things that replace materials for racing, and those parts are cracked by being torn by heat. There is a way to earn time, but it is not easy, as it is burning at high temperature in the exhaust, the propeller shaft and DOJ (Constant Velocity Joint) also have a fever, unless you think about the cooling system We are currently taking measures against thermal hazards.
The secret measure of time earnings to compensate for power shortage in the engine was technology called anti-rag. Then the engine characteristics should be different from the previous one. The turbo lag disappears and the response improves suddenly. If that happens, you will also need to change the gear ratio of the transmission.
ーーTatsumi
Now that the gear ratio on hand is only 17 years specification, I am making it, because I want to use engine characteristics more effectively, it is difficult to adapt and it takes time.
Gears were sequential and adopted paddle shift from 17 years. Was there no problem around that?
ーーTatsumi
The adaptation of the paddle came into the hands a lot, and it did not have any problems such as durability last year, but since the gear shift shock was big, it seems that we were using the clutch at the driver’s discretion. If it is big, there is a change in behavior and a movement different from FR and FF comes out. The driver uses the nerve and the burden is also big. In addition, the driver in addition from the magnitude of the shift shock, “This is 24 It is also true that there was anxiety that there is no time to go? “Although durability was sufficient in reality, now the problem has been improved and the speed change has been smoothly made, so this year the merit of sequential I think that you can make good use of it.
ーーTatsumi
After all, I am reviewing with the rear differential, the center differential, the front differential. In the test at Fuji Speed Way of January it was a reply that the driver is a good feeling about the differential, the thing that I did the rear differential, the center differential I guess weakened, eventually it is better to defeat weakly. I have the impression that it is strong and effective, but I think that is a little obstructing when giving up time. Since Audi uses Torsen I understand the reason why it is mechanically connected, but it is good to be able to move in four wheels free. I think that moving four wheels separately is the original form. If you restrain it, I think that it is understeer if it is AWD and that it does not necessarily need LSD originally because it stops when it slides out after all.
The background of this idea is interesting in the story of Petter Solberg who was active in WRC.
ーーTatsumi
Petter Solberg had always requested that we want to weaken the differential, but the engineer slipped this much on the data so we had a conversation saying weakened, and Petter said that it can run faster if sliding. The engineer said that idleness was loss, I think that sliding is okay, it is better to slip the tires. The racing tires are different. Trading with the evolution of the tires, Even though it got traction, lateral force comes out, I think that it is no problem even if you slip 40% or 50%, although it is not surprising though, it is useless only with data. With data emphasis, only a part can be seen. All the races are connected, so I think that way of thinking is also necessary.
They have also begun to improve the brakes to reduce the time.
ーーTatsumi
I lose engine power, earn with anti-lag, earn even brake and earn cornering. The racing driver uses the left foot brake but I can not stepped on with the master back, so I took the master back in 18 years First, because the carbon brake is prohibited by the rule, it is size up. Both the rotor and the caliper will do the pad Although the friction material is also important, but because the sliding area increases, it increases from 54 mm to 64 mm. Then wear resistance will increase and effective radius will increase, so it will be effective and last long Therefore, when selecting a pad, when stepping on MAX there is no problem, but a minute When I stepped on, when you want, such as use in the approach of cornering, feeling a little effectiveness is not enough now, is a place called looking for friction material
How is the problem with the tires?
ーーTatsumi
Last year’s tire did not have any problem tire. The trust for last year’s tire is high as it runs in 10 lap Nürburgring and it was not degraded, but considering that this year will be held in the cold season, We are developing a tire that can be used at low temperatures.
ーーTatsumi
I think that the appearance has changed a lot, and the front mask also reduced the Cd value considering the aerodynamics, changed the air intake holes that were on the top and changed it to be taken in from the rear door for rear differential cooling. I think that it became beautiful. In the wind tunnel I make it by simulation with the data made with CAD. Cd also decreased though I feel that the downforce is not enough a bit, but the driver feels just right That’s why I will look at the actual running test for the future.
ーーTatsumi
Even if good results are tested in the wind tunnel at 180 km / h, we must develop it based on the fact that it is not an equal measure in the race, that is, it is only one criterion, that is, it is 180 km / h constant in the race It is speedy passing by moment. It is an intense deceleration that exceeds 2 G towards one owner from 270 km / h, 180 km / h is only a moment, and the posture of the vehicle So there is no point in talking about wind tunnel data at 180 km / h, unless you can not imagine a three dimensional engineer, it is not clear unless you listen to the driver’s opinion.
Thus SUBARU WRX STI NBR Challenge 2018 has steadily been developing machine. Perhaps a shakedown test will be released in March. It is also a great pleasure to finish up the machine where director Tatsumi’s idea could reflect. The actual day is May 12th and 13th.
＞ 2018 Advanced technology of STI to explore from race car
＊Supported by SUBARU TECNICA INTERNATIONAL
