A major design programme by the Mahindra Racing Formula E team for their third season M3Electro car has clearly worked, with the team third in the all-electric championship ahead of the season finale in Montreal. That powertrain is a race-winning solution and has dominated podiums throughout the season.
These impressive feats are rendered all the more startling given that only Renault e.dams and ABT Schaeffler Audi Sport – each boasting a wealth of global automotive manufacturing and motorsport resources behind them – are ahead of the Indian outfit.
In large part, the success of the team in season three is due to clever packing of its advanced powertrain and careful selection of partners, who include tech supplier Magneti Marelli. The McLaren motor used in seasons one and two by Mahindra has been dropped for season three and replaced with one from the Italian firm – and the team hasn’t looked back.
“Our season two used an evolution of existing technology from McLaren, driven by time constraints rather than outright performance targets,” explains Vinit Patel, chief engineer at Mahindra Racing. “For season three, we started with a blank piece of paper. The process began even before the first race of season two. The FIA is actually quite open with regards to the future regulations. The governing rules are fairly basic, with some capacitance and voltage limitations and not really much else except the physical envelope of the standardised car dimensions.”
Patel describes the development process: “We split the requirements into three main areas; transmission, motor and control electronics. We carried out a principles-led analysis of what we needed from the motor and inverter to get the best result on track. This evolved from a basic spreadsheet to thousands of laps of simulation to test variables such as mass, centre of gravity, RPM range, torque range, thermal characteristics and efficiency maps. Eventually, we were able to hone in on some key requirements, and ultimately a shortlist of suppliers that had technology that could meet those requirements.”
Step forward Magneti Marelli, which calls on its long history in F1 to put Mahindra’s season three powertrain ahead of the pack.
“The main challenge in designing a Formula E racing car motor is finding the best compromise between packaging requirements, weight, efficiency and dynamic performance,” says Patel. “Many iterations were worked through with our partners at MM before a suitably optimised design was agreed.”
A Formula E car must capture energy under braking to extend the range of its race battery. This process, known as “regenerative braking”, is very different from most conventional racing cars and therefore requires a different approach.
“Regen requirements need full analysis and simulation to account for the increased duty cycle on the motor and other powertrain components, especially reverse forces not seen in normal motorsport applications,” Patel notes. “This means it is vital to account for it to correctly life the components and specify correct materials and dimensions of the pack.”
Mahindra’s analysis process began in September 2015; the specification was fixed in December and the first prototype ran on the test bench in April 2016 before being run in the development car in May. Nearly 4000km of track testing with the new powertrain was completed over a combination of private and public test days, equivalent to two full seasons of racing. That reliability has clearly carried through to the racing season.
While Formula E is still in its relevant infancy, the design process for the bespoke prototype powertrains is not far different to that found in F1 or WEC, explains Patel: “The design principles are the same: understand the application and simulate to know your end requirements. So while F1 has a more complex energy management structure with the current turbo and ERS systems, the design process is not much different as long as the understanding is in place.”
Electric motors are, of course, not new. Electric cars have been with us for decades, so can Formula E really do much to advance the technology? Patel thinks so.
“Formula E is a sport and, as such, it means you look for technology to give the competitive edge and we are willing to take more risks or pay higher costs for this advantage,” he explains. “For motors there is a lot of scope for improvement in materials, motor design techniques, new magnetic technologies and design optimisation. All this leads to motors with higher potential performance, lower weight and ultimately higher efficiency. Formula E allows an arena for advancing these areas at a faster pace than the product- and business-orientated world because performance comes first, not financial profits, in racing.”
- Manufacturer: Magneti Marelli
- Type: permanent magnet synchronous motor
- Weight: confidential
- Casing: aluminium alloy
- Dimensions: confidential
- Cooling: liquid cooled
- Power: 200kW max
- Testing: 4000km on track – equivalent to two full race seasons