The Indianapolis Grand Prix circuit is what one might describe as two circuits for the price of one. That is, part of the circuit consists of the famous Indy 500 oval speedway incorporating turn one and the pit straight, but run in the reverse ...
The Indianapolis Grand Prix circuit is what one might describe as two circuits for the price of one. That is, part of the circuit consists of the famous Indy 500 oval speedway incorporating turn one and the pit straight, but run in the reverse direction. The other part of the circuit is a series of tight infield loops joining the two ends of the speedway section, with the similar slow characteristics and hard to overtake characteristics of Hungary but with even less grip. From a technical standpoint, the track demands two different set-ups on the car in one lap for the most competitive lap times; but of course these have to be combined in order to create one compromise set-up that works as well as possible for both the circuit characteristics.
"The infield section is very difficult to overtake upon, so even though you could set up the car to run much faster by using more downforce for the infield, you cannot afford to create too much drag for the straight and thus lose the all-important top speed. This would allow other cars to slipstream past and get ahead under braking for the first turn, which is about the only practical place to overtake on this track with a wide entry and several lines possible into the corner, " explains Ferrari's technical director, Ross Brawn.
The whole problem is further complicated by the fact that the infield section has very little grip from the asphalt, so it is necessary to run a soft tyre. Thus, excessive tyre wear can become another major issue for the race. Last year, the Ferrari team ran a more conservative medium hard compound to be safe. This year they are "going for it" and planning a soft and super soft compound tyre that has been specially developed by Bridgestone for this race and tested at Mugello last week.
"The lack of track grip and the need to run less wing here means that the cars slide around a lot and that results in a high wear rate and blisters. Last year, McLaren took a chance and ran the faster, softer tyres and won the race, but they were worn down to the canvas at the end, " pointed out Ross.
This aspect of the track means that the aerodynamic set-up of the car must also be very different between qualifying and the race. For qualifying, the cars are set-up with more downforce for the infield and, although slower on the straight, this results in a better overall lap time. For the race, especially if the cars are starting from the front of the grid, it's a lower downforce set-up that is preferable. This ensures the cars do not lose out to their rivals on the straight. The car might be less comfortable to drive through the infield, but it is a better alternative than having everyone overtake you down the straight.
With less downforce carried than the team would normally use for the infield section of the circuit, there is a lot of delicate work to be carried out in practice to make sure that the traction control system, differential settings and mechanical grip of the chassis is optimized to prevent the car sliding about as much as possible and thus minimizing tyre wear. They key factor to the downforce set-up is not only judged on the straight line speed compared to rival teams, but also the speed out of the last corner onto the straight. If the driver is unable to get onto the straight quick enough, he becomes an easy target for a following car, even though he might have a better eventual top speed down what is the longest straight on the F1 calendar, where slipstreaming can still play a vital role.
"When we first went to Indianapolis we were concerned about the effects of the banked corner onto the straight regarding suspension loads and tyre pressures etc, but it turned out not to be an issue as the corner is comfortably flat out for the drivers, and the speed not high enough to cause any concern about suspension or tyre loading," explains Brawn.
While the Indianapolis circuit layout does not appear to be anything too challenging from a driver standpoint, it presents a special challenge from an engineering point of view and strategies used. It is also the longest pit-lane in Formula One, where speeds were increased to 120 kph instead of 80 kph last year, but it was still a 26-second hike plus the time spent stopped for tyres and fuel. With the long, fast pit-lane entry corner that is only separated from the track by a strip of grass, there is a possibility that the pit speed limit might be reduced this year for safety reasons. That move would almost certainly negate any possibilities of a two-stop race.
The weather can also be very unpredictable in this part of America. Cool and perhaps damp autumn conditions or an Indian summer heat-wave are both possible, so that can also have a big influence on the race strategies the teams use as well as the choice of tyre compounds. The number of pit stops in the race might not only be depending on the pit lane speed limit, tyre and chassis performance, but also the circumstances in the race itself. A group of slower traffic in the infield can be so hard to overtake on any part of the track that an early stop or a second pit stop can also be a better alternative than waiting to find a way past.
Mechanically, the Indy track is not particularly tough on the chassis, the brakes and gearbox are not stressed heavily and the suspension on the smooth track surface and gentle kerbs is also well within its design limits. However, the long straight at this track can cause particular problems for the engine, which stays on full power for a longer single period more than any other track in the calendar.
The sudden heavy braking to slow speed resulting in less oil circulating to cool the engine puts even more stress on the hot parts, as Rubens Barrichello's engine failure two laps from the end of last years race was to show. Special attention is now paid to the engine control software at this point of the track to help eliminate this unique problem which is only found elsewhere at the similar Magny Cours track when braking hard from the fast straight into the hairpin.
With race data gathered from the previous first two events, the task is not as daunting for the engineers as it was their first year at Indianapolis, and with a win and two second places already to their credit around the new Indy track, the engineers of the Scuderia Ferrari Marlboro team have already shown that they know how to cope in more ways than one with the technical difficulties of this legendary track.