When all of Formula E’s cars share the same energy source (the Williams-provided battery), the same limit on peak permitted power (200kW in qualifying; 170kW in the race) and the same chassis, how do some cars appear to be more glued to the surface than others? The answer is complex but can be summed up in one often-used phrase: set-up.
“Set-up” encompasses a wide range of adjustments. Physical settings range from the angle the wheels are set at to meet the road surface, how far the car is positioned off the ground and the amount and rate of travel in the suspension to the angle of aerodynamic surfaces and brake balance.
On the software and electronic side of things, Formula E cars can run different power maps, which tell the powertrain how to behave in different situations and which can deliver differing amounts of power and torque to suit different requirements. Regenerative braking can also be varied and, as energy is only captured from the rear axle, the brake bias has to be adjusted when regen levels change.
The functions operated by the various buttons and paddles on the Formula E steering wheel can be altered to produce different reactions, giving the drivers far more control over what they want their car to do.
All of these factors are fine-tuned by the engineers to accomplish a specific set of goals and in light of the characteristics of a particular track. Ultimate straight line speed may require a different set of parameters to ultimate efficiency, for example, depending on the location, nature of the circuit, surface, ambient temperature and a host of other variables. Keeping the driver happy by delivering a car that he or she feels comfortable with is also vital.
In conventional top-level motorsports, teams may have two or three days to play with set-up adjustments, and they may take a completely different approach to qualifying than to the race. In Formula E, there is such limited track time on race day that, when it comes to set-up changes, less is often more.
“Set-up changes between qualifying and race really depend on where you get to on the grid,” notes Vin Patel, chief engineer at Mahindra Racing. “If you are happy with your 170kW race laps and your 200kW qualifying laps with the same set-up, you wouldn’t touch it. At some circuits however (Buenos Aires is the stand out example), you might trade some downforce for drag reduction and straight line speed. You may also go for a lower drag set-up in the race to help your efficiency and to get a better toe behind other cars.”
Once the set-up has been honed for a particular track over the course of the morning’s two free practice sessions, the solution settled on for qualifying will largely remain the same for the race, Patel says: “Other than aero, nothing else usually changes except regen tuning. This is affected by driver preference, too: some might prefer a lot of regen when qualifying so the braking system feels consistent all day while others prefer to just rely on the brake pedal alone for their flying quali lap.”
Teams are free to choose whichever car they like to start the race with – they don’t have bring the car they qualified with to the grid.
“The driver is allowed to complete up to two laps in 170kw power mode before his single 200kW quali lap,” Patel explains. “One 170kW lap is mandatory (ie the out lap to get from pit exit to timing line), which is used to bring the brakes and tyres up to temperature and get the hang of any tiny set-up tweaks that may have been introduced after the second free practice session. Warming the brakes and tyres, even with the relatively robust low profile rubber worn by the Formula E cars, is crucial to yield maximum grip and corner entry attack. At tracks with a longer laps, some prefer to hang back and preserve the life of the tyre slightly more for their flying lap.”
The number of tyres permitted for use by teams is limited in Formula E, to help both reduce waste and cut carbon emissions in logistics by reducing the amount of freight required. While the treaded tyres are remarkably consistent over a race distance, there is still some strategy involved in choosing how to use them.
“Everyone will try to save new (or nearly new) tyres for qualifying,” Patel says. “On a track like Beijing, a brand new set of tyres could cut the lap time by as much as 0.8s compared with a nearly-new set. That means that drivers and their engineers have to account for this in FP2, knowing that there will be extra grip and pace in qualifying just through a tyre change. Sometimes, this means a small set-up tweak; at other times, it’s just down to the driver to anticipate where the increased grip will be.”
When it comes to qualifying, although the car has been already been set up, the engineer’s job isn’t over. “Before the 200kW qualifying lap, the engineer will remind the driver he or she is permitted to complete the last sector of the slow lap in 200kW mode, as well as providing reminders to switch settings for power maps, brakes and regen,” Patel goes on. “With very limited telemetry available to teams, however, once the set-up has been determined, it’s up to the driver to ensure he presses all the right buttons – in qualifying and in the race.”