When it comes to Formula E, keeping cool is more than a style aspiration: it’s also a vital part of race day management for teams and drivers.
“In Formula E, we have three types of race,” explains Vin Patel, engineering chief at Mahindra Racing. “As well as the race you see on track, we’re also racing against energy and temperature.”
Ensuring that drivers don’t scorch through their permitted energy during a Formula E race has been well documented. What has been less examined is the impact that heat makes on powertrain performance. It was an issue that presented itself very early for the Mahindra team, when Karun Chandhok was forced to slow down in the closing laps of the Beijing 2014 race due to thermal issues.
“As with other top level motorsports, where the powertrains are working right at their limits, each component must operate within a strict temperature range,” Patel explains.
While Formula E racing cars aren’t burning fuel within the engine and don’t have engines with thousands of intricate moving parts, significant heat is generated when energy is drawn and returned to the battery and when the electric motors are being pushed hard (the McLaren-built unit in Mahindra’s M2Electro spins beyond 19,000rpm). What’s more, in-built safety systems in the car automatically restrict powertrain performance when thermal limits are breached, causing a dramatic drop off in speed on track while the car cools down.
So, just how do you keep an electric racing car cool?
“We use cooling systems not too dissimilar to those in conventional racing cars (and road cars) to maintain ideal operating temperatures,” Patel says. “All the thermal management systems in season two Formula E cars work in the same way, using radiators and cooling fluid in closed loops. As the fluid is passed through the powertrain in tubes, it absorbs heat radiating from the components. Once the hot fluid reaches the radiators in the sidepods, it is cooled by air being forced across the surfaces of the radiator elements. Now cooled, the fluid returns to the powertrain to pick up more heat.”
The cooling process begins long before the drivers are tearing around the track, with a specific set of procedures in the garage. The cars must be kept cool while they are recharging too, which adds another layer of complexity to race day.
Patel explains: “We need to keep the cars cool before and after all track running. We aim to begin each track session with the powertrain as cold as we are allowed under the regulations. To achieve this, all teams have supplementary cooling devices, often a combination of external pumps and fans to cool the fluid either directly or with airflow over the radiators. As in sports such as F1, the procedures must be carried out with military precision to safeguard performance.”
In season one, the weak link when it came to thermal limitations was the motor in qualifying and the battery in the race. With manufacturer teams permitted to change parts of the cooling system for season two, for some the focus of thermal issues has changed. “For us, the most critical component is the battery, which uses a common cooling package provided by Spark Racing Technologies and Williams Advanced Engineering,” Patel says. “Manufacturer teams are only permitted to create bespoke parts for the cooling of the other powertrain components, such as the motor and gearbox.”
The driver does have a part to play, however. While the driver isn’t able to dial the cooling up or down, he can lift and coast to avoid drawing as much energy from the battery. During the race, this is usually enough to keep the powertrain in the correct thermal operating window.
Ambient temperature plays a big role, especially with some of the exotic locations that Formula E visits. “In Beijing, we had cool ambient temperatures, rarely above 20⁰C,” Patel says. “That meant less monitoring was required throughout the day. Places such as Putrajaya, Punta del Este and Buenos Aires are very different. Last season in Buenos Aires, the ambient temperature was 34⁰C, which was very difficult to deal with. Drivers have to be much more watchful during the race to keep everything working smoothly.”
While some teams have sophisticated modelling procedures to simulate conditions before each race, experience counts too. “After a full season of racing, all teams have a lot more experience which helps engineers judge just how far the thermal limits can be pushed,” says Patel, before sounding a note of warning. “However, as the Putrajaya round showed, sometimes getting it wrong by just a single degree Celsius is enough to ruin your race.”
With battery design unlikely to be opened to manufacturer teams until season five, when it comes to thermal management garage procedures, cooling elsewhere in the powertrain and driver awareness will continue to be critical to race day performance in Formula E.