At 7,200 feet above sea level, the Autódromo Hermanos Rodríguez in Mexico City is presenting teams in the FIA World Endurance Championship with a unique set of challenges.

Teams had their first opportunity to hit the track today to try to work out whether the hours of homework they put in to prepare for this weekend’s race has paid off.

Audi struck the first blow by finishing 1-2 in the first practice while Porsche bounced back to lead in the afternoon.

Brazilian ace Lucas di Grassi is making his second visit to Mexico City this year after racing in the FIA Formula E round (and initially winning before being disqualified for a technical infringement).

“The track itself is very tricky and the high altitude makes it low grip and difficult to drive. There is no room for a mistake and you have already seen a big crash today,” di Grassi said.

“It is a challenging track with traffic with the track density because it is so short and the difference in performance is bigger.”

Toyota were the first to strike trouble today when Stephane Sarrazin crashed the No.8 TS050-Hybrid – forcing the team to change the monocoupe.

While the higher altitude affects the engine performance of the naturally aspirated cars in LM P2 and GTE, downforce is also an issue for every car – regardless of your power plant.

“You have 20 per cent less air so you have 20 per cent less downforce. It is proportional and you also have less drag. With the hybrid you don’t lose anything because there is no air involved and with the turbo you can get it back,” di Grassi said.

“Against a normally aspirated car the relative gain is much bigger but in terms of grip you have 20 per cent less downforce so every time you brake and turn you cannot put the energy into the tyre like you want to.

“The car is very light and it is very easy to make a mistake. It is also tricky to overtake so it is a combination of low grip and tight corners.

All the manufacturers have gone to great lengths to try to maintain as much performance as possible.

“We – like Porsche – are trying to optimise the car for the track,” di Grassi said.

“It is also very special here because of the cooling. With less air you have less heat exchanging in the radiators, intercoolers, brake disc, everywhere – we have a lot of parts made for Mexico only that we can only use here.

“Audi has done a fantastic job back home to make sure the car was perfectly set for here and we have to get the most of it in the race.”