In Mexico City, an altitude adjustment – for ABB Formula E

The highest racetrack in the ABB FIA Formula E Championships series requires drivers and their teams to account for thin-air challenges

Each of the 10 race locations in the ABB FIA Formula E Championship series presents unique challenges that drivers and teams must overcome to be competitive. But the Mexico City race on March 3, this season’s fifth stop for the international circuit, may pose the most demanding conditions of them all.

To an innovative technology leader like ABB, though, the challenges are an opportunity to demonstrate key benefits of the environmentally responsible Formula E cars.

The race will test the special strategies required of drivers and racing teams when competing at the series’ highest altitude: about 2,200 meters, or more than 1.4 miles above sea level. The thin air at this elevation wreaks havoc with the cars’ carefully engineered aerodynamics, as well its vital cooling systems.

The effects of altitude will be noticeable even to spectators who make the trip to see the competition firsthand. A racing fan who drives the 320 kilometers from the Gulf Coast town of Tecolutla to the Autódromo Hermanos Rodríguez track will encounter a steep vertical climb.

That trip will tax the capabilities of a typical passenger car, with the engine losing 20 percent of its horsepower as the air thins during the ascent and the engine is shortchanged of the oxygen needed to support combustion in the cylinders. (The driver and passengers might have sympathy for the engine when they find themselves short of breath from the altitude change while climbing to their seats in the grandstand.)

Mexico City’s altitude has long challenged fossil-fueled race cars at this track, where the Formula 1 grand prix circuit first competed in 1963. But the thinner air has no sapping effect on the horsepower of the fully electric Formula E cars, which draw all of their strength from an on-board battery pack. As a result, Formula E cars have the same amount of horsepower here as they do at sea level.

Which is not to say that the electric race cars don’t face other challenges because of the altitude.

A series of trade-offs

One downside of the reduced air density, for Formula E and Formula 1 cars alike, is the loss of downforce – the beneficial aerodynamic effect of the car’s wings and body panels that aids cornering traction at high speed. To compensate, the racing teams can adjust the angle of the front and rear wings to regain some downforce. But doing so will also increase aerodynamic drag – the wind resistance that reduces top speeds.

The trade-off of downforce versus drag is a calculus that each team makes using sophisticated computer simulations. Generally speaking, the teams have found that the loss of downforce has a greater effect on lap times than any gains realized by reduced drag. All of this information will factor into the strategies of the Formula E drivers and their teams in Mexico City, as they race through the 17-turns of the 2.1-kilometer course, with lap times of just over one minute.

Another major challenge is cooling the motors, transmissions, electronics and, especially, the brakes. While the motors of electric cars don’t generate nearly the heat of a combustion engine, they do run hot. But in Formula E, little can be done to compensate for the reduced cooling effect of thin air because the rules do not allow the addition of larger radiators or opening up the air intakes. The problem is compounded, Formula E teams report, by the fact that in the thinner air, the electric racecars cars reach their braking points going faster. So the brakes must work even harder – and become hotter.

All that said, the high-altitude difficulties are more pronounced for Formula 1 teams, which will next race in Mexico City in October. Though the turbocharged V6 engines of contemporary Formula 1 cars do not suffer as severe a power loss as their predecessors, they are far more stressed than at sea level.

To offset the reduced cooling effectiveness at altitude, the Formula 1 teams must use larger ductwork and openings in the body panels to keep temperatures under control, a measure allowed under Formula 1 rules. But those adjustments increase aerodynamic drag. To compensate for the reduced air density at Mexico City’s altitude, Formula 1 teams generally set up their cars for maximum downforce, which further increases drag.

For the Formula E electric cars, some decisions, like tire choice, are far simpler. For each of the two cars that a Formula 1 driver brings to a race, teams are allowed to use as many as 40 tires per car for the event – with nine choices of tire compounds to choose from, depending on weather and track conditions.

For the electric cars, in contrast, each is allotted just a single set of four new tires (plus two used tires from the previous race) for each of a driver’s two cars to last the entire event: practice, qualifying and race. And the tires are made to be recyclable afterward. Together with their complete absence of tailpipe pollutants, the Formula E cars make a powerful case for motorsports that are sustainable as well as providing a technology laboratory for the transportation future.

The main similarity shared by Formula E and Formula 1? The high-altitude offsets are all part of a complex strategy.

Differences between Formula E and Formula 1 (infographic available for download below)
Differences between Formula E and Formula 1 (infographic available for download below)

That’s why, in Mexico City on March 3, the adjustments the teams have made ahead of time could prove almost as crucial to the outcome as anything the drivers do once that the starting lights signal that the race is on.

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