NEW YORK—Racing cars came to Red Hook this past weekend as Formula E held its season four finale, the NYC ePrix. Although the event is only in its second year, the Big Apple is fast feeling like home for these all-electric race cars, and once again we saw championship-deciding races play out against the Manhattan skyline.

But this event also marked a different sort of finale—the end of Formula E's first chapter as the series prepares to retire the cars it has been using for these last four seasons. When season five gets underway in Saudi Arabia this December, Formula E will have a new vehicle in the spotlight: one with more power, wild looks, and enough battery to make mid-race vehicle swaps a thing of the past.

Formula E's current reality

Unlike other racing series, Formula E exclusively races on temporary street tracks in city centers, because city centers are where electric vehicles make the most sense. (Yes, the Mexico round is the exception that proves the rule, but that permanent circuit is in a pretty urban part of Mexico City.) Not all of those city centers have proved welcoming; races in Miami and Montreal were one-offs, and the London ePrix lasted but two years. But the series signed a 10-year deal with New York City, and, by building the course around the Brooklyn Cruise Terminal, the impact on local residents from road closures and the like are minimal. (The course itself is slightly modified from last year, including longer straights that increase the track length to 1.5 miles, or 2.4km.)

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Alastair Staley/DS Virgin

David Aguilar/DS Virgin

Sam Bloxham/LAT/Formula E

Sam Bloxham/LAT/Formula E

Formula E

Jaguar Racing

Audi AG

Elle Cayabyab Gitlin

Jonathan Gitlin

Elle Cayabyab Gitlin

Sam Bloxham//LAT/Formula E

Sam Bagnall/LAT/Formula E

Elle Cayabyab Gitlin

Jonathan Gitlin

As its name may give away, Formula E exclusively races electric cars. Back in season one, these open-wheel single seaters were all identical: a carbon-fiber chassis designed by Spark and built by Dallara; 200kW (268hp) electric motors from Renault that send power to the rear wheels via a five-speed gearbox sourced from McLaren; and lithium-ion batteries developed by Williams Advanced Engineering. At the time, cost and weight concerns meant those batteries were—and still are—just 28kWh. (As a result, each driver has needed two cars at each race, swapping between them mid-way.)

Since then, the series has begun to open up the technical regulations to allow the sport to become an engineering testbed for overall EV development. To prevent budgets from escalating into F1 or LMP1 territory, for now only some areas of the cars can be developed. Even in the current season four, every team has to use the same chassis, its integrated battery, and the same bodywork.

These restrictions prevent fortunes being spent on marginal gains like aerodynamics—the tracks being too short for it to be much of a factor—or potentially massive gains from battery development. Everyone involved knows opening up the battery rules would soon see costs soar out of control, so even the series' Gen2 car will use a spec battery: this time, a 54kWh lithium-ion pack from McLaren Applied Technologies, Lucid Motors, and Murata that has enough capacity for a complete race distance.

But each team has been free to develop its own motor, gearbox, and control electronics, with almost all of them choosing to do so. As you might imagine, that has made the sport an attractive place for automakers and engineering companies to invest time and money. Jaguar was the first OEM to sign up in season three. This year, Audi went from a toe dipped in the water to playing for real, and next year BMW will do the same. Season five will also see Renault replaced by corporate cousin Nissan, and season six is going to get very interesting, with the arrival of Porsche and Mercedes-Benz.

Today, the key to winning in Formula E is to understand that "compared to other series, it's an efficiency race, not a power race. That means the best efficiency from battery to wheel," says Vincent Gaillardot, technical manager of the Renault e.dams team. And he should know; his success in other series and formulae—which earned him the title of "the engine whisperer"—translated over to Formula E. The series' first three team championships were won by Renault e.dams.

"You've got a narrowing of areas of gain, and we're at the point where everyone is so close, no one has a big advantage," explained Allan McNish, team principal of the Audi Sport ABT Schaeffler team.

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Jonathan Gitlin

A sensational Saturday

This season wasn't quite so good for Renault's own team. But it also supplied powertrains to the Techeetah team, which used them to very good effect. Coming into Saturday's race, Techeetah led the teams' championship, and its driver, Jean-Éric Vergne, led the drivers' championship. His closest competition was from DS Virgin Racing's Sam Bird (who, you will remember, won both races at last year's NYC ePrix). Fortunately for Bird, Vergne had to start from the back of the grid, both Techeetahs having had their qualifying times disallowed for using too much energy.

Unfortunately for Bird, he was also racing with last year's tech, and the British driver had to ultimately settle for ninth. "Today was a bit disappointing, but I can't complain too much. It was just one of those races," he told Ars. "We didn't do any update really for this season; we're running last year's kit. It's a bit heavy, and it's not quite as efficient as some of the others. DS has still done a stunning job—and the team has done a stunning job, too—but in order to fight, it's difficult. When the race gets to that length [Saturday's race was the longest of the season] we know the limitations of our car, and a long race is not good for us."

Vergne, by contrast, fought his way through the pack and finished fifth, clinching the drivers' championship in the process. "When I crossed the line I honestly didn't know I had won," Vergne explained. "My engineer told me, 'I guess we've done it,' so I said, 'What do you mean?' Then [teammate André] Lotterer went past me and clapped, so I knew something was up. When I found out I was speechless. I enjoyed the race, but obviously, it was very tough. Some drivers were quite hard and over-consumed energy to try and not let me by. It was actually really complicated, a real fight unlike in Zurich—today, the drivers were tougher!"

Audi also had a good day. Daniel Abt led the first half of the race, but a small mistake was all the opportunity that his teammate and defending champion Lucas di Grassi needed. di Grassi—who started in eighth place—got past Abt at turn 11 and went on to take the win; his teammate had to settle for second place. "The Audi Sport ABT Schaeffler car was just a rocket today," di Grassi said.

"I had good fights with [Venturi's Tom] Dillmann—good fights with a lot of the drivers, in fact," he continued. "The second stint was a bit weird—in Formula E, it makes no sense to open a gap, because, if a safety car or any other disruption happens, you've wasted energy to open that gap. So I was just trying to make sure that Daniel was at just the right distance, but then after [DS Virgin driver Alex] Lynn's crash, it's just a flat-out race to the end, which was very different. Daniel made a mistake in braking at Turn 6 and went a little bit wide through the dust. Then his tires were bad for the next segment, before the back straight, and I knew that it was a good moment to attack."