The BMW iFE.18, with which the BMW i Andretti Motorsport team won the opening round of this season’s ABB FIA Formula E Championship, consists of many features developed internally at BMW, as well as the standard parts stipulated in the regulations. For BMW i Motorsport engineers, the Racing eDrive01 drivetrain wasn’t the sole development focus.
In addition to the drivetrain, the rear end and the rear suspension were the two areas where the BMW i Motorsport engineers had the greatest leeway for their own developments. To keep a lid on costs, the chassis, battery and tires are standard Formula E parts, but the engineers at BMW i Motorsport designed the rear axle, including suspension and shock absorbers, themselves and integrated the drivetrain in the rear part of the car. As each drivetrain has its own individual properties, each team is responsible for integrating the drivetrain into the rear-end structure of the cars and finding a cooling setup that suits these properties.
The team can configure typical setup parameters on the chassis of the BMW iFE.18, such as spring rates, anti-roll bars, ride height, toe and camber. The chassis setup plays an important role in achieving maximum mechanical grip on the tarmac surfaces of the street circuits, some of which are uneven compared to permanent racetracks. It is also important that both the chassis and the rear-end structure are robust enough to cope with driving over aggressive curbs and light contact with barriers on street circuits.
The Generative Design process was used when developing various components. This made it possible to directly derive the design of the components from the load cases, with the assistance of computers, to incorporate the experience and expertise of the BMW i Motorsport engineers, and then to produce the components from aluminum using a 3D-printing procedure. In the case of other components, this combination of know-how and technology has made it possible to efficiently integrate various functions, such as in the cooling circuits, in very few parts.
The experience possessed by BMW i Motorsport engineers in the development and production of fiber-reinforced plastics really came into its own in the design of the rear-end structure. The structure is light, and a range of functions have been integrated directly into the structure.
The topic of sustainability also plays a role in the development of the BMW iFE.18. BMW i Motorsport engineers continue to work closely with their colleagues in production to increasingly integrate renewable resources in suitable components.
Another major in-house BMW development is the electronic, brake-by-wire braking system. The introduction of this system represents a big technological step for Formula E and, in this regard, takes it to the same level as Formula 1 and the LMP1 category in the FIA World Endurance Championship.
As of Season 5, brake-by-wire controls the relationship between mechanical braking force, when the driver pushes the brake pedal, and the braking effect generated by energy harvested during deceleration and braking. When the motor recovers energy from the braking process during the race, it basically functions as an additional brake on the rear axle of the car. Previously, drivers had to manually adjust the brake balance to balance the additional braking effect.
The integration of the brake-by-wire system and, above all, the software logic developed by the BMW i Motorsport engineers, significantly increases the regeneration potential. Finding the best possible configuration of this software is crucial to be able to contest the entire race distance with maximum power from the battery, while complying with the amount of energy permitted by the regulations.
In practice, overcoming this challenge requires the engineers to achieve the best possible relationship between speed and energy management. Their task is to calculate a race time optimization with the limited amount of energy. It is important to keep sight of all the race action – to read the data and to anticipate what may be coming – to then decide with the driver when it is better to save energy and when to attack, to make up positions or open a gap to the cars behind.