Chinese GP: Williams technical preview

Talking Technical

Car dynamics
Average turn angle indicates the average angle of a circuit's corners expressed in degrees. The higher the average turn angle, the more acute the corners in the circuit's configuration and the greater propensity for understeer to compromise lap time. At Shanghai, the average turn angle is 133.690, against a season average of 1100, ranking it as the circuit with the second highest average turn angle across the Championship. As a consequence of the circuit's physical layout, an understeering car balance will have a high punitive effect on lap time.

The end of straight (EOS) speed at Shanghai was 306kp/h in 2008. Shanghai ranks as having the 7th fastest EOS speed on the 2009 calendar, and this is one indicator of the wing level typically selected to optimise the downforce/drag ratio. As the average speed around Shanghai is the 13th fastest of any of the tracks, a compromise is required.

Pitlane & refuelling strategy
The pitlane length and profile (i.e. corners in the pitlane entry) contribute to the determination of the optimum fuel strategy. The pitlane loss at Shanghai is approximately 23 seconds, the 6th most penalising pitlane in the Championship. To complete a normalised distance of 5km around the Shanghai circuit requires 2.55kg of fuel against an average of 2.42kg per 5km across all circuits this season, making the circuit the 4th least demanding track of the year in terms of fuel consumption.

Safety car
Another key contributor to the determination of race strategy is the likelihood of safety car deployments, which are influenced by weather considerations, the availability of clear run-off areas that allow racing to continue while recovery takes place and the circuit profile, especially the character of the entry and exit into turn one at the start of the race. Since the race debuted on the calendar in 2004, there have been 2 safety car deployments in China, both in 2005, making it statistically unlikely that the circuit's character will induce safety car periods. The first two races of this season have already seen 3 safety car periods, however, so anything is possible!

Temperature, pressure & humidity
It is a long observed tradition that drivers arriving at Interlagos complain about a lack of grip and an absence of engine power. Having become acquainted with a baseline of engine and aerodynamic performance during the season, the climb to 750 metres above sea level for one of the final races can, courtesy of the reduction in air density, rob a Formula One car of engine power, aerodynamic performance and cooling. The losses can come close to double digit percentages and thus have a very real impact on car performance. Air density is a factor of the prevailing ambient temperature, which varies most significantly by season, air pressure which is closely linked to altitude and, to a much smaller degree, by humidity. Thus if races are run at the same time each year, the factor that tends to have the greatest bearing on air density is elevation. Like half the races on the calendar, Shanghai is close to sea level, just 10m above, and has an average pressure (1,014 mbar), so engine power will be good. A change for 2009 is that the race has been moved from October to April. Ambient temperatures are therefore expected to be cooler which will have an influence on the tyres.

-credit: williams