Mexico City’s altitude (over 7,000 feet above sea level) poses a unique challenge for the high-tech machines in the LMP1 class that they’ve never before encountered, as top-level sportscars make a return to the venue for the first time since the early 1990s.

High altitude equals less drag, so you can run much higher downforce levels than you normally would on a layout like the Autodromo Hermanos Rodriguez. It also means also less oxygen for the engines and for cooling, so that’s going to stress the brakes more than ever.

All that downforce, combined with what’s regarded as a low-grip surface, should also spell a tough time for the tyres too – always a key aspect of endurance racing.

“Mexico represents a new challenge for us and all teams in WEC,” says Toshio Sato of Toyota. “Even though we bring our ultra-high-downforce package to Mexico, we can expect some impressive top speeds due to the thin air.

“We have not run our TS050 HYBRID at such altitude before and the track is new to us so the team will be working hard in practice.”

His opposite number at Porsche, Andreas Seidl, adds of the challenge: “Compared to normally-aspirated engines, our turbocharged engine loses less power, but cooling is an issue because of the thin air with less oxygen.

“This goes for the powertrain as well as for the brakes. Necessarily, drag is a lot lower. This makes it difficult to provide the downforce you want in the corners, but on the 1.2-kilometre straight we will see high top speeds.

“The circuit has a high full throttle percentage and the grip level will increase significantly unless it rains, which is something to expect as well.”

Top speeds set to approach 225mph

Event promoter and LMP2 owner-driver Ricardo Gonzalez drove the circuit this week in an LMP3 car on a promotion day.

He estimates LMP1 speeds will border on “360kph [224mph] at the end of the straight, while GTs could be in the 290kph [180mph] region”.

Gonzalez adds: “It's a track where passing is difficult, it is complicated. The racing line does not help for that. There are sections where it’s very tight, especially in the area of ​​the stadium, where you can barely fit a car.

“One thing that surprised me is how easy the temperature of the brakes and engine climbs, and how difficult it is to reduce it. That will play a role in the strategy.”

State of play

Porsche comes into the Mexican weekend in a position of power. The #2 919 Hybrid crew of Romain Dumas, Marc Lieb and Neel Jani holds a comfortable 33-point lead over the #8 Audi trio of Oliver Jarvis, Loic Duval and Lucas di Grassi.

Dumas says: “I’m looking forward to discovering the new track. First in the simulator and then the real thing.

“It will be a big challenge with the altitude. It will be different for the engine, the cooling and the downforce level and difficult for the drivers. No-one has yet driven an LMP1 car 2,000 metres above sea level.”

The best-placed Toyota is the #6 car of Kamui Kobayashi, Stephane Sarrazin and Mike Conway, which is another 11 points behind the Audi, although the Japanese marque enjoyed a difficult time at the Nurburgring round.

“I hope we will be back on the pace,” says Sarrazin. “Whenever a series goes to a completely new track, it’s always very challenging and exciting.

“The practice sessions will be particularly busy because we want to get a lot of detailed information about how our car behaves on this track. The unusual factor in Mexico will be the altitude, which makes it tougher for the drivers, but I’m prepared for this.”

Webber on a mission

The big story for the second half of the WEC season will likely be the fightback of the reigning champion #1 Porsche of Mark Webber, Brendon Hartley and Timo Bernhard.

They won last time out at the Nurburgring, but are still 77.5 points in arrears of the leading sister car.

“We learnt a lot with our new high downforce package at the Nurburgring,” says Webber. “It worked very well.

“Mexico is a different layout. We’ll have to see how the capacity of the engines work at high altitude in terms of diesel and petrol. It looks low on grip and it will, therefore, be interesting to see what downforce level people are on.”

The WEC 6 Hours of Mexico takes place this Saturday, and you can follow all the action straight from the track on Motorsport.com.