Altitude affects engine power as there is less oxygen, which mean that engines have more trouble “breathing”. The share of oxygen in gas remains roughly the same, but with lower pressure, and therefore lower density, there is less air available and oxygen is less present. An estimated 1% of power is lost for every 100 metres above sea level. That applies to internal combustion engines of course. For turbocharged engines, things work a little differently. Turbo forces air into the engine, with the same pressure to that used at low altitude. Power therefore remains the same whether the race is at sea level or 2,000 metres higher. However, the turbo has to work a lot harder to make up for the lack of air. The lower the air density, the more the turbo needs to work fast to maintain the pressure.

The increased demand on the turbo could means it end up being less reliable. The same goes for energy retrieval elements. Porsche works driver Romain Dumas, winner of the 24 Hours of Le Mans 2016, is familiar with the problem. He won the Pikes Peak hill race in Colorado this year, which culminates at 4,000 metres above sea level. The 20-kilometre hill climb puts cars under even more pressure than an endurance race. Drivers have to manage the car’s lack of power as well as their own breathing difficulties. Most have an onboard oxygen supply. That won’t be necessary in Mexico, although the added difficulty means track action promises to be breath-taking.

Photo: The 6 Hours of Mexico is set to be a great race in all classes. The spirit of Le Mans heads west.