ABSTRACT The paper presents the main results of a study on the simulation of energy efficient management of on-board electric and thermal systems for a medium-size passenger vehicle featuring a parallel-hybrid diesel powertrain with a high-voltage belt alternator starter. A set of advanced technologies has been considered on the basis of very aggressive fuel economy targets: base-engine downsizing and friction reduction, combustion optimization, active thermal management, enhanced aftertreatment and downspeeding. Mild-hybridization has also been added with the goal of supporting the downsized/downspeeded engine performance, performing energy recuperation during coasting phases and enabling smooth stop/start and acceleration. The simulation has implemented a dynamic response to the required velocity and manual gear shift profiles in order to reproduce real-driver behavior and has actuated an automatic power split between the Internal Combustion Engine (ICE) and the Electric Machine (EM). Typical parallel hybrid technology functions, such as Stop&Start, regenerative braking and power assistance from the EM have all been implemented in the GT-Drive model. After model calibration and validation versus the available experimental data, the energy management strategies of such a hybrid configuration were investigated. The results obtained for the New European Driving Cycle (NEDC) and a Real Life Driving Cycle (RLDC) have been discussed, in terms of fuel economy and performance.INTRODUCTION The sustainable exploitation of the environment and energy is a central concern in industry. Although energy is fundamental for the existence of humans it is also at the heart of many environmental issues in the 21st century ([ 1,2]). The automotive industry, which is driven by more and more stringent international emission standards, is reacting by adopting new and advanced technologies. One of these concerns Hybrid Electric Vehicles (HEVs) i.e. vehicles characterized by a double power-source: thermal and electrical ([ 3, 4, 5]). HEVs attempt to couple the benefits of traditional Internal Combustion Engines (ICEs) with those of Battery Electric Vehicles (BEVs) in order to meet future EU CO2 targets and stringent emission limits, while overcoming the main disadvantages of BEVs, i.e. the reduced driving range and the need for a dedicated recharge infrastructure. However, the HEV system is complex and requires suitable energy management to properly exploit all the advantages expected from the hybrid drivetrain. In this framework, simulation plays a key role in identifying the optimal hybrid operating strategies, where the primary design targets are fuel economy, emission reduction and improvement in the vehicle performance (including acceleration, driving range, operational flexibility, and noise) ([ 6, 7, 8, 9, 10]). In this work, fuel economy and the performance of a parallel hybrid architecture have been analyzed by means of a specifically developed GT-Drive model, which is able to reproduce real-driver behavior and determine the power split Analysis of Energy-Efficient Management of a Light-Duty Parallel-Hybrid Diesel Powertrain with a Belt Alternator Starter2011-24-0080 Published 09/11/2011 Alessandro Ferrari, Edoardo Morra and Ezio Spessa Politecnico di Torino Claudio Ciaravino and Alberto Vassallo General Motors LLC Copyright © 2011 SAE International doi:10.4271/2011-24-0080Downloaded from SAE International by Univ of California Berkeley, Sunday, July 29, 2018between the ICE and Electric Machine (EM), taking into account the battery performance limitation due to its operating temperature and State Of Charge (SOC). The traditional starter has been replaced with a high-voltage Belt Alternator Starter (BAS) in a light-duty diesel engine passenger car, but no significant changes have been made to the drivetrain layout. The resulting parallel hybrid architecture makes it possible to adopt engine Stop&Start operations, regenerative brakin