The powertrain electrification is currently not only taking place in public road mobility vehicles, but is also making its way to the racetrack, where it’s driving innovation for developments that will later be used in series production vehicles. The current development focus for electric vehicles is the balance between driving power, range and weight, which is given even greater weighting in racing. To redefine the current limits, IAV developed a complete e-powertrain for a racing MX motorcycle and integrated it into a real drivable demonstrator bike. The unique selling point is the innovative direct phase-change cooling (PCC) of the three-phase e-motor and its power electronics, which enables significantly increased continuous power (Pe = 40 kW from 7,000 rpm to 9,000 rpm) without thermal power reduction. The drive unit is powered by a replaceable Lithium-Ion round cell battery (Ubat,max = 370V) with an energy storage capacity of Ebat = 5 kWh. The battery system is completely integrated into series chassis and equipped with immersion cooling including cell temperature monitoring.
The power transmission to the wheel realized by a single speed transmission and hydraulically actuated multi-plate wet clutch. The driving range under racing conditions (driving time) on a dirt track circuit is min. tTrack = 35 min. By means of an exchange battery pack a quick change of the battery is realized and so more than one race stint at racing weekend could be managed. The total weight of the motorcycle is located at the 450cc four-stroke class (mbike ~113 kg), whereby the handling is implemented with a state-of-the-art chassis and suspension analogous to the classic fuel MX motorcycle. In addition, the drivability by means of adjustments to the e-motor characteristics (power and power output), recuperation, etc. is largely freely adaptable.
Within this paper, the design, construction & integration, and thermal management of the new drivetrain for an MX motorcycle will be presented in detail.