Powertrain explained: M3Electro

Blueprints Mahindra Racing December 2016 M3Electro powertrain cheat sheet Current E

Here’s the two minute technical history of Formula E.

In season one, all teams used a spec chassis and spec powertrain. The chassis was built by Spark Racing Technology (via Dallara), the race battery was supplied by Williams Advanced Engineering, the motor and inverter came from McLaren Advanced Technologies (based on the firm’s P1 supercar), and the five-speed gearbox was from Hewland Engineering.

Battery energy use was set at 28kWh; peak permitted power was 150kW in race mode and 200kW in qualifying mode. Race-winning advantages were found by teams in chassis set-up and energy strategies rather than powertrain secrets; however, with all-new tracks, modelling and simulation were of limited use to engineers.

In season two, teams who had been approved as constructors could build their own drivetrains; of the 10 teams who began the season, seven raced with their own solutions. The battery continued to be supplied by Williams and the same chassis will remain in use until the end of the sport’s fourth season. Mahindra’s M2Electro made an evolutionary step from the season one car through use of a powertrain designed with McLaren, married to a four-speed Hewland gearbox and boasting several innovations to further increase efficiency.

Several different configurations could be seen throughout the paddock, with transmissions ranging from direct drive through to five speeds. Most teams used a single motor but two teams chose to try out twin-motor solutions. Peak permitted power was lifted to 170kW in races and continued at 200kW in qualifying; permitted energy use was unchanged at 28kWh.

Season three is now underway. As before, the chassis and battery suppliers remain unchanged; the race batteries have been refreshed and upgraded by Spark (via Williams), although the energy and power figures remain the same. The rate at which energy can be recovered under regenerative braking has jumped, however, from 100kW to 150kW.

Mahindra Racing’s M3Electro represents a revolutionary step compared with its season two effort. In place of the McLaren motor is now a six-phase unit from Magneti Marelli, and the Italian tech firm is supplying the inverters too. A transverse two-speed transmission package was chosen, while overall drivetrain mass has been decreased by 40% compared with M2Electro.

Next month, we’ll bring you a detailed look at how the M3Electro powertrain was designed and developed. In the meantime, here are the vital statistics for the M3Electro:

Motor

  • Magneti Marelli six phase MGU
  • Transverse orientation
  • Peak RPM increase of 14% (compared with M2Electro)
  • Peak torque increase of 38% (compared with M2Electro)

Inverter

  • Two inverters, each controlling three motor phases
  • F1-derived technology (SicMOSFET high-frequency switching architecture)
  • Bespoke DC junction assembly

Cooling

  • Parallel closed systems for inverters and motor
  • Bespoke ducting
  • Bespoke radiator

Battery

  • Supplied by Spark (via Williams Advanced Engineering)
  • 28kWh permitted energy use
  • 150kW peak permitted regenerative power
  • 170kW peak permitted power (race mode)
  • 200kW peak permitted power (qualifying mode)
  • Liquid cooled

Transmission

  • Bespoke two-speed gearbox
  • Pneumatically actuated barrel/fork shift
  • Transverse layout
  • Bespoke carbon fibre casing

Rear suspension

  • Bespoke lightweight, unequal length wishbones
  • Low friction bearings
  • Pushrod-actuated coilover dampers, with bespoke rockers and anti-roll bars

Software and driver controls

  • Multiple software functionality and performance updates for new drivetrain
  • Steering wheel has increased complexity and driver interface functions

Weight

  • 880kg with driver and ballast
  • Battery weighs less than season two due to refurbishment

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