The challenge of Interlagos
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| Renault's Robert Kubica |
Interlagos may be one of the shorter laps on the calendar at just over 4.3km, but there’s no shortage of challenges for the drivers and engineers. With one of the longest straights of the season, combined with slow hairpins and a couple of high-speed corners, finding the sweet spot at Interlagos is all about making the right set-up compromise.
The perennial question facing teams at the Brazilian Grand Prix is whether to choose straight-line speed over optimum lap time. It’s a challenge that has been made easier this year thanks to the wonders of the f-duct, but it’s still front-of-mind for the engineers, as Chief Engineer Alan Permane explains: “We usually set the car up to achieve the optimum lap time, and the way the R30 works with our f-duct should still allow us to achieve good straight-line speeds. It means we can have the downforce in the slow infield corners but still be competitive enough to attack or defend down the straights."
Finding the sweet spot for the mechanical set-up is a similar story with a balance necessary to deliver a car that works well in the low and high-speed sections. “As always, it’s the low-speed corners where the most lap time can be found, so it’s important that your car has good traction," says Alan. “But with high-speed corners such as turn 11, which has an apex speed of 230 km/h, the car needs to be responsive and you can’t afford to have a set-up that is too soft. As ever, it’s about striking the right balance."
It’s those quick corners with the high g-forces that make Interlagos a tough race physically for the drivers. The forces are highest in turns six and seven where the drivers have to endure 4.5g of lateral acceleration for 4.5 seconds. The anti-clockwise layout also subjects the drivers’ necks to the opposite loadings experienced at clockwise circuits for many of the corners. As a result, don’t be surprised to see extra cockpit padding appear on the drivers’ headrests to help them through the 71 laps of the Grand Prix.
On the engine side, the long main straight means that engine power is a critical factor at Interlagos with the cars on full throttle for 16 seconds from the exit of turn 12 until the braking zone for turn one. On top of that, all the engines must cope with the effect of running at altitude because the circuit is situated around 800 meters above sea level.
“Running at altitude costs an F1 engine around 8% of its power," confirms Remi Taffin, Head of Engine Track Operations. “Despite losing this power, the altitude actually has a positive impact on the engine because the moving parts suffer less. There is less air entering the engine, which means less pressure and less stress on the pistons, conrods, crankshaft and every moving part."
The engine engineers will also work hard over the weekend to deliver engine mapping that gives the engine good torque delivery, especially at low revs. “There are a couple of tricky low speed corners so the engine needs to be drivable at the lower end of the rev range from 8,000 to 13,000 rpm," says Remi. “Getting smooth power delivery will help to ensure a stable car balance and good performance through the twisty middle sector."
Robert Kubica: “Anything can happen at Interlagos"
Robert, let’s look back on Korea. What were your thoughts on the race?
For me it felt like the race was divided in two halves. The first part was very difficult because I had big problems with the overall grip and I struggled to keep the car on the track. In the second half I gained quite a lot of ground when my tires were in better shape for the last ten or 15 laps of the race. I managed to finish fifth, which was a good reward for our efforts. Of course we would like to be more competitive, but I think overall we have to be happy to have scored a good amount of points after the difficulty we had at the start of the race.
Looking ahead to this weekend, how do you think the R30 will perform at Interlagos?
Brazil is a bit of a strange track and it’s really difficult to predict how we will perform. There is a long straight out of the last corner where the f-duct will give us lots of gain and this is also where the power of the engine will be important. I think that we might have a lottery with the weather because Brazil gets unsettled conditions at this time of year, so it’s likely we will have some wet running, as we did in 2009. When it rains the track has very poor grip and you have to be lucky to get the perfect balance with the car.
What are the keys to a good set-up in Brazil?
It’s a difficult track for setting up the car because of the long straight and the uphill sections of the track. You have to choose between top speed, or running a lot of downforce and gaining through the corners, so it’s very difficult to balance those two things. The track has a bit of everything – low speed, high speed and it’s kind of an old school circuit so there are quite a lot of places where you can gain lap time. But, as I said before, it’s quite difficult to get everything in the right place with the balance and the car set-up.
The Brazilian Grand Prix always has a great atmosphere on race day. Tell us about your memories of racing there…
You are very near the fans because the grandstands are very close, which makes the feeling on the grid very special. 95% of them are cheering for Brazilians, but it’s still a nice atmosphere. I had a good result there last year, which came as a big surprise. It will be difficult to repeat it this year, but as I said the weather can play a big role at Interlagos and anything can happen there.
Vitaly: “It will be great to experience Interlagos for real"
Vitaly, how are you approaching the next race at Interlagos?
When you have tough races like Japan and Korea, you can’t wait to get back in the car to forget those bad memories, so I’m really looking forward to Interlagos. But it’s difficult to know what to expect because I’ve never been to Brazil before and it’s another new challenge for me. It’s a famous circuit because there have been so many great races there, especially in the last few years with the championship being decided. I remember watching these races on television so it will be great to experience it for real.
What are your views on the track layout?
It’s not a very long lap – just over 4km, but there are a lot of different corners in the lap. It’s also quite undulating so I think this makes it more interesting to try and find the limit in some of the corners. There is a very long straight and a good overtaking opportunity into the first chicane, so clearly the f-duct will very important at this track.
Have you done any special preparation for this race?
After Korea I went straight to Enstone to see the engineers and to talk about Brazil. The team have lots of data from last year, which is useful for learning the track because you can see the gears, the braking, the line, and you can start to understand the lap more. I also went back in the simulator to help me learn the Interlagos circuit. It only takes an hour to know the track pretty well and to have the confidence to start pushing.
Renault F1