Improving longitudinal dynamics of conventional vehicles in comparison to electrified vehicles to meet customer behavior

Automobile manufacturers progressively focus on a downsizing strategy to meet the EU's CO
₂
fleet requirements concerning type approval consumption cycles. The reduction in naturally aspirated engine power due to reduction of displacement is compensated by application of turbocharging. However, the downsizing of conventional engines implicates major challenges regarding longitudinal dynamic characteristics. An example of this circumstance is the delayed turbocharger-induced torque reaction which leads to a partially poor response behavior of the vehicle during acceleration operations (tubo-lag). It is important to focus conventional drive train design on real customer driving again. Electrification of the drive train increases the response behavior, while simultaneously CO
₂
emissions are reduced. Thus, an electric engine provides the desired torque almost without delay. The advantage over a conventional vehicle is particularly noticeable at low engine speeds. This paper complements current dynamic criteria (e.g. acceleration 0-100 kph, elasticity 80-120 kph) illustrated in manufacturer information by realistic acceleration maneuvers to objectify customer-oriented transient dynamics. As a result, longitudinal dynamics experienced by a driver is adequately described. In this contribution we present a simulation based method for evaluating these realistic dynamic criteria. This method extends an existing stationary total vehicle model by a specifically adapted engine torque gradient model to consider transient influences like the boost pressure of the turbocharger. This contribution focuses on an evaluation of electrified technical measures (e.g. use of 48V in combination with an electric charger) to strengthen the customer-oriented longitudinal dynamics in conventional vehicles. By applying the validated transient simulation tool we determine the extent to which the instantaneous torque response of conventional vehicles can be adapted to the torque response of fully electrified vehicles. Design measures (e.g. gear ratio and vehicle weight) and technical electrified measures (e.g. e-charger) both improve longitudinal response in daily driving situations. But for each vehicle design a varying set of measures improves dynamics best considering effectiveness.