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Philip Griefnow and Jakob Andert
RWTH Aachen University, Germany
Posters & Accepted Abstracts: Adv Automob Eng
The engine stop-start system was a major advance to face the challenges of fuel saving of ICE vehicles. This technology requires significant changes of the electrical system like electrical energy management and cycle resistant starter batteries to ensure a reliable restart and sufficient energy supply during vehicle standstill. Latest developments are focusing vehicle sailing with engine off. This allows expanding engine off period as well as reduction of driving resistance during vehicle deceleration. An engine stop while sailing reduces fuel consumption significantly, but it also leads to considerably higher load on the electrical system. This investigation analyses the impact on fuel consumption and the electrical system by vehicle measurements and simulations. Basis is a state-of-theart C-segment vehicle with DCT, enhanced stop-start and engine idle sailing. The enhanced stop-start system turns off the engine shortly before vehicle stop. The sailing function declutches the engine in situations without driver torque request while the engine remains in idle. Enhanced stop-start and sailing idle are evaluated by vehicle measurements under real world driving conditions. The battery as the most important electrical component is additionally validated on a component test bench. A powernet simulation is set up and calibrated based on experimental data of vehicle and component tests. An engine off sailing algorithm is implemented in the vehicle simulation environment. The effects on powernet voltage stability, energy balance and cranking ability are evaluated and compared to the estimated fuel consumption reduction. Starting from simulation analysis this study defines requirements for prospective automotive electrical systems to further reduce fuel consumption and emissions.