At an altitude of more than one-mile, LMP1 manufacturers are forecasting this weekend’s inaugural Six Hours of Mexico to be one of the most demanding races on machinery in the five-year history of the FIA World Endurance Championship.

The new-for-2016 event, held at the historic Autodromo Hermanos Rodriguez in Mexico City, is at 7,382 feet (2,250 meters) above sea level, which will cause significant strains on power and cooling, and even an affect on aero balance, according to competitors.

“It’s like going into the unknown for sure,” Porsche LMP1 team principal Andreas Seidl told Sportscar365. “The FIA allowed for this year, as an exception [for this race], that you can run special cooling. Everyone is preparing this and I think we’ll have to see where we end up.”

With none of the teams able to test at the revamped 17-turn, 2.674-mile circuit, or even at a location with similar elevation, there’s a degree of uncertainty on whether cars from Porsche, Audi and Toyota will be able to withstand the challenges the conditions will present.

The majority of WEC rounds are held nearly at sea-level, with Interlagos (2,427 feet) and Nürburgring (1,712 feet) having been the two highest locations the championship has previously raced at.

Even Utah Motorsports Campus (4,226 feet), which Audi previously ran in 2006-08 (when known as Miller Motorsports Park) with its diesel-powered R10 TDIs, is roughly half the elevation of Mexico City, but was before the era of hybrid technology and small-capacity turbos.

“In Mexico, you will see a car that needs a lot of cooling because of the low density,” explained Audi Sport’s Head of Aerodynamics Jan Monchaux.

“There will be many openings there. Because the air is so thin, and by definition you have less drag and downforce acting on the car, we will probably be running maximum downforce, everything we can, because it’s still going to be quicker.”

Monchaux said having sufficient cooling impacts a number of components, including the LMP1 car’s energy recovery systems, which rely on braking power.

“I’ll be glad when Mexico is behind and we have finished the race with both cars because the cooling demands on the engine side, but also the braking side, are non-traditional,” he said.

“Basically because of the density, you are missing 25 to 30 percent transfer rate of air going through your brake discs or radiators.

“For the engine, for the turbo, for the brakes, for all the people generating heat and needing cool it… I hope we’ve made a sufficient step.

“It’s the most stressful event for me because they say, ‘Look, you need to cool the car!’ We need to cool the car but have a strong performance. Mexico is going to be a very special performance.”

While all three LMP1 manufacturers will be on relatively even ground by each having turbo engines, which perform better in higher altitude, it will still play a factor in terms of reliability, according to Toyota Gazoo Racing technical director Pascal Vasselon.

“Watching the F1 race [in Mexico] last year, it’s clearly an issue and we’ve tried to anticipate it the best we could,” Vasselon told Sportscar365.

Toyota recently completed a two-day test at Magny-Cours, as part of a simulation for the Mexico City race.

“We’ve figured out how much more cooling we’ll need, in percentage, and we checked that,” Vasselon said. “We don’t need to go to [similar elevated] places to evaluate how much more cooling we will need.”

Even with the additional cooling allowances permitted for the event, teams are taking a wait-and-see approach in hoping their cars will have a good enough balance between performance and cooling.

“Of course you always need to develop a performing car,” Porsche’s Seidl added. “But the biggest challenge is to make it to the end, even in a six-hour race as we’ve seen [earlier this year]. Luckily I think it’s the same for all three manufacturers.”