Shanghai provides a new challenge
Renault Chinese GP preview - 2
September 20, 2004

Pat Symonds and Denis Chevrier talk of the challenge that a new circuit such as Shanghai provides. Renault, third in the constructors’ championship, are desperate to beat rivals BAR and regain the runner-up position in the standings.

The Engineer's View with Pat Symonds: Shanghai

Racing on a new circuit remains one of the most appealing challenges for any F1 engineer, and when that circuit is both brand new, and in a new country, it merely adds to the enjoyment and the challenge. Of course, as we have discussed previously, our work begins with a simulation of the circuit, but beyond the mathematical perspective that such simulations provide, we also take a more generalized, subjective view.

For Shanghai, we have had our usual challenges of simulating the circuit using track maps that do not always have the required level of detail. Once we have established the general speeds of the corners, we begin to design a set-up aimed at achieving the best possible lap time but also giving us our best possibility of racing well. Looking at Shanghai, the circuit is dominated by two straights, one over a kilometer in length and the other around 600m – indicating that a competitive top speed will be an important factor to protect our position. However, there are also twelve corners, and many of them lead directly into one another – while also being surprisingly long for a modern circuit of this type.

Looking at circuit maps, it is clear that the characteristics of the lap vary as it progresses. The first part is full of slow corners, from the long, tightening turns at the end of the pit straight, to the relatively straightforward hairpin at turn 6. After this, though, we enter a much more challenging sector, with three left- right-left corners that are taken at sequentially decreasing speeds, and will certainly represent a significant part of the lap time. The drivers will need to find a flowing line through here. After this sequence, a short straight leads to a tight left, and then a very long right-hand corner that introduces the final sequence of the lap. This corner leads onto the main straight – which is over a kilometer long – and it will be important to get a good exit as the next corner, a tight Magny-Cours style hairpin, will be a good overtaking opportunity. This slow corner leads to another straight, followed by a medium-slow left-hander leading into the second long straight and the end of the lap. These different parts of the lap will prove a good all-round test of the cars’ and drivers’ abilities.

Their implications for car set-up are also tricky to assess. The circuit initially demands high downforce settings to give an optimum lap time, but the penalty in lap time for reducing downforce in order to gain straight-line speed is relatively low (what we call the ‘aero profile’ of the circuit is relatively flat), and this means that by the time we come to race day, I think the downforce settings are more likely to be termed ‘medium downforce’. The circuit’s sensitivity to engine power is very similar to that of Melbourne, that’s to say in the bottom quarter of the circuits we visit but the fuel effect – the penalty in lap time for carrying a given quantity of fuel – will be quite high, largely due to the importance of the fast corners we mentioned earlier, and the average lap speed should be quicker than in Bahrain. Indeed, that circuit was also dominated by the issue of brake usage. Shanghai should be more normal in this respect, and the total braking energy is slightly below average. Equally, the long straights will give the brakes time to cool.

Looking at tire usage, the total energy the tires must absorb per lap is expected to be quite high. However, the race is only 56 laps – and we therefore anticipate tire usage will be similar to the circuit such as the Nürburgring. The distribution of front/rear tire usage should be relatively well balanced, but may be biased slightly rearwards owing to the fact that a number of the corners open out as the cars are under hard acceleration. This characteristic means that the balance of tire usage shifts from front to rear as the cars go through the corner, which subjects the rear tires to high lateral loadings as well as the traction demands. Equally, the acceleration out of the slower hairpins will place high stresses on the rear tires.

The final factor to consider is the weather. The climate in Shanghai is a reasonably normal four season climate and by the end of September, we can probably expect to see maximum temperatures during the day of around 25°C. Being a port, Shanghai is obviously at sea level and therefore atmospheric pressure is normal, though the rainfall can be quite high. September is the month when the area moves out of its rainy season and while the average rainfall in October is 61mm, September sees 156 mm of rain, while we can expect to see 9 days during September with rainfall greater than 1mm. Any delay in this seasonal transition could mean changeable weather for the race weekend.

Of course, we must remember is that while such preparatory work is essential, it remains theoretical – reality can be quite different once grip levels are established, and the drivers know the lines they can take. The circuit looks to be a difficult one to learn, and we can expect a rapid evolution in lap times both as the grip levels increase and the drivers become more familiar with it. It appears to be a track where mistakes will be easy to make, and by Sunday evening, we could well view Shanghai as rather an interesting driver’s circuit.

The Engineer's View with Denis Chevrier: Shanghai

For the engine team, preparation for a new Grand Prix such as the inaugural race in China begins on the dynamometer. Once a theoretical optimum racing line has been established using circuit maps and simulation tools, and once we have made our estimates of grip levels, we can then predict the duty cycle the engine will undergo at a given circuit. From this starting point, we run a simulation on the dyno in order to identify any defining characteristics that might potentially be troublesome for the engine.

However, from what we do already know, Shanghai will not be an “engine circuit”. The duty cycle is not particularly severe, and the time spent at full throttle by the drivers is unlikely to exceed 60% of the lap – a figure that corresponds to the season average. The length of the main straight does exceed the average value, however, and is indeed relatively high at around 16 seconds – which should see the cars reaching approximately 325 or 330 kph.

Much of the rest of the circuit is very twisty, which will make the downforce compromise tricky to judge. However, the number of faster corners, combined with the high number of heavy braking and acceleration phases will make the fuel effect reasonably high – around 0.45s for an extra ten kilograms of fuel. Similarly, the numerous acceleration phases through corners which open out, and the slow speeds at which acceleration begins, mean that a strong torque curve and smooth power delivery will be essential to maintain car balance and give the drivers good speed on corner exit.

Overall, our expectations are that we will encounter an average type of circuit for the engine in Shanghai, but of course, our predictions and simulations cannot be full comprehensive, and some significant factors remain unknown at this point.

Firstly, the ambient temperatures are uncertain. It could be very hot, and the slow speeds at various points around the circuit could mean cooling become a problem, which means we will need to plan for a number of different cooling solutions.

Secondly, the wind speed and direction can always make a difference to engine performance and particularly the choice of gear ratios. Our first day’s running will give us an indication of this parameter, as well as true values for corner speeds, and it may prove necessary to fine-tune our choice of gearbox ratios on Friday night prior to qualifying. The nature of the curbs, and how much the drivers can use them at high and low speeds, will also influence this decision, as this can lead to over-revving.

One other interesting point is that the start and finish line appears to be positioned relatively close to the first corner. The run down to this tightening curve seems to be of the order of 300 meters, and this will make it particularly important to qualify well as the overtaking opportunities at the start could prove to be limited.


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