RÉMI TAFFIN, RENAULT SPORT F1 HEAD OF TRACK OPERATIONS
The main factors of Interlagos are the altitude and heat, both of which are potentially destructive characteristics for the new Power Units. Whereas the altitude once gave the cars and engines an easier ride as less power was produced, it now works against us. A turbocharged engine pressurises the ambient air to the same level inside the turbocharger and compressor, ensuring there is always the same amount of oxygen content in the air inside the engine. With around 10% less oxygen in the air in Brazil, the turbo has to spin at a much higher speed to generate the same power, rotating at very close to its maximum. We can consider the ‘high’ races such as Spa and Austria as interim tests, but at 800m above sea level, Interlagos is another step (before Mexico in 2015, that is) so we conduct specific tests in the dynos at Viry to check settings, firstly to ensure reliability and then to get the performance settings right.
The temperatures in Brazil can also be very hot. High temperatures are not necessarily a big problem, but the combination of the heat and high altitude drastically reduces the air density. To produce the same power the revs will be a lot higher, putting huge stresses on the internals of the ICE. We’ll be looking very closely at this phenomenon in the dyno, where we can create both phenomena.
While the ICE and turbo are under a lot of pressure, the other parts of the PU are not too stressed at Interlagos even if this year the pit straight will be challenging now engine are turbocharged. The MGU-K can recover energy through the short corners, and the MGU-H will have ample opportunity on the short bursts of throttle between the turns.
Doing your homework before you arrive will pay dividends, particularly on the long, uphill pit straight that provides one of the best overtaking opportunities. We’re relatively comfortable going to the race, but we’ll also be checking everything very closely during each session!
In addition to the high altitude, the rise and fall of the local topography gives a total elevation change of 150ft over the course of a lap.
There have already been several off camber corners this season where the lubricants are ‘squashed’ to one side, but there are no more obvious examples of this phenomenon than the first corner of Interlagos, the Senna S for the oil system and the last long left hand corner leading to the pit straight for the fuel system. The off camber Senna S drops sharply downhill, putting the cars an angle of approx 30°. Higher fuel and lubricant levels may be used to safeguard against any momentary stall as the fluids drop suddenly to one side of the tank, and fuel collectors are often designed with this corner in mind as it is the most severe of the season.
Interlagos is the bumpiest permanent track of the year. Monaco and the other street circuits feature ‘natural’ bumps over manhole covers and drains, but the high ambient humidity, geographic position and relative lack of use of Interlagos means the track develops large contusions. Due to the low ride height of the cars and the hard suspension, running directly over the middle of a bump makes the car temporarily ‘take off’. Even if it’s just for a nano second, with no load running through the wheels the engine suddenly hits the rev limiter, which puts the internal parts under stress. This is however less severe this year now engines are running “lower” revs.
Rene Arnoux became the last driver to use turbo power to win at Interlagos when he took victory in 1980 with the Renault RE20. When action returned to the track in 1990 it was the normally-aspirated era. Nigel Mansell won with the Renault V10 in 1992, with Michael Schumacher, Damon Hill and Jacques Villeneuve on the top step from 1995 to 1997. In the V8 era Mark Webber won in 2009 and 2011 and Sebastian Vettel in 2010 and ’13 for Red Bull Racing.