MERCEDES' MEGAMETER EV

FIRST RIDE I Mercedes-EQ Vision EQXX

- FRANK MARKUS

Behold the most efficient Mercedes ever: the Vision EQXX. On Tuesday, April 5, this experimental concept car drove 626 miles from its birthplace in Stuttgart, Germany, up and over the 6,900-foot Gotthard Pass in Switzerland to the French Riviera on a single 100-kWh battery charge.

The car averaged 56 mph by adhering to all speed limits, peaking at 87 mph on a no-limit stretch of autobahn. It made two 15-minute bio-break stops, arriving in Cassis having consumed only 88 percent of the battery with 87 miles of range remaining (certified by German TÜV authorities). We traveled to the Nice design center that penned the exquisite EQXX to learn how this impressive feat was accomplished and to get a sense of how close the forthcoming EQC sedan might come to achieving similar results.

The EQXX team's overarching goal was a single-digit kWh/100 km consumption figure. The Riviera Run yielded 8.7 kWh/100 km (241 mpg-e). The team prioritized its efforts proportionately to the forces acting on such an electric compact sedan at speed: 62 percent of the energy expended goes to overcome aerodynamic forces, 20 percent to overcoming the vehicle's weight and rolling resistance, and 18 percent goes to drivetrain losses.

Front wheels typically create one-third of a sedan's aero drag. The easiest (and ugliest) way to fix this is by fairing the wheels into the bodywork with skirts or spats, but the team in Nice managed to minimize wheel drag with smooth, unvented wheel covers, by specifying the tire sidewall contours and demanding all labeling be carved into the rubber, and by insetting the rear wheels almost 2 inches relative to the fronts, putting them in the fronts' "wind shadow." The considerable overhead-view taper of the greenhouse makes possible those sensuous rear shoulders that mask this "design don't" (it also benefits aero), but at considerable cost to rear seat shoulder room.