As congestion increases and commute times lengthen with the growing urbanization, many customers will look for effective mobility solutions. Two-wheeler are one of the solutions to deal with these issues, in particular if equipped with electrified powertrains for minimized local noise and air pollutant emissions.
Scooters powertrain technology is predominantly based on Spark Ignition Engine (ICE) associated with a Continuously Variable Transmissions (CVT) and a Centrifugal Clutch. Nevertheless, even though CVT gives satisfaction in simplicity, fun to drive, cost effectiveness and vehicle dynamics, its efficiency is an undeniable drawback. Indeed, a conventional CVT is wasting more than 50% of ICE effective power in customer driving conditions. Consequently, those vehicles have high fuel consumption relative to their size, and are equipped with overpowered and heavy internal combustion engines, allowing a large area for further improvements.
Therefore, IFP Energies nouvelles (IFPEN) has developed a physically based simulation tools for scooters powertrain analysis, design and control. ICE model is based on an analytical calculation for indicated efficiency and frictions. CVT and centrifugal clutch are modeled using existing LMS Amesim components and a specifically developed physical transfer function. The final model is in a good agreement with real figures, such as fuel consumption and dynamics behavior of each system. Therefore, these methods and tools have proven to be relevant and time effective to study the impact of powertrain innovations on those two-wheeler performances.
By using these methodological apparatus, IFPEN evaluates the benefit of powertrain evolution such as innovative transmission or hybridization. Taking into account ICE operation limits, and comparable fun to drive behavior with respect to scooters equipped with a CVT, IFPEN estimates a huge impact of a modification of the transmission on fuel consumption (reduction of around 1L/100km on WMTC), proving the benefit of a new concept proposed by IFPEN (not described in this paper). Moreover, the simulator also evaluates the electrification benefits, particularly in urban conditions.
Finally, the modeling approach through detailed simulation platform and an energy optimization tool developed in this paper aims at helping the design of an innovative concept providing equivalent drivability with a better fuel consumption, both on certification cycle and in real use conditions, taking into account the next powertrain evolutions for sustainable and energy effective individual mobility.