Natural high - the challenge of Interlagos 02 Nov 2010
Interlagos may be one of the shorter tracks on the calendar at just over 4.3 kilometres, but theres 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 the Sao Paulo circuit is all about making the right set-up compromise, as the Renault team explain.
The perennial question facing teams at the Brazilian Grand Prix is whether to choose straight-line speed over optimum lap time. Its a challenge that has been made easier this year for some teams thanks to the wonders of the F-duct, but its still front-of-mind for the engineers.
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, explains Renaults chief engineer Alan Permane. 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, its the low-speed corners where the most lap time can be found, so its important that your car has good traction, says Permane. 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 cant afford to have a set-up that is too soft. As ever, its about striking the right balance.
Its 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, dont 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 metres above sea level.
Running at altitude costs an F1 engine around eight percent of its power, confirms Remi Taffin, Renaults 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 provides 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 Taffin. Getting smooth power delivery will help to ensure a stable car balance and good performance through the twisty middle sector.
The final challenge of the lap is the long left-hand drag up the hill onto the main straight, which can make it tricky to pick up the last bit of fuel in the tank, especially during low-fuel qualifying runs. We will need to check the fuel pick-up in free practice, explains Taffin. We dont expect any problems with the fuel system we have been running, but its better to be safe than sorry.
The Brazilian Grand Prix weekend gets underway on Friday.
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