Downsizing Opportunities for Drivelines with 42V Starter/Alternator

The change of the net voltage offers substantial opportunities for energy and thus fuel saving at three levels. In this paper, however, we are especially interested in discussing a third contribution, which is based on the layout alternatives offered by the fact that a 42V board net in combination with an integrated starter generator (ISG) additionally offers so far unprecedented properties to conventional vehicles, since this structure allows a similar operation as a parallel hybrid vehicle. The concept of such a 'mild hybrid' allows to resize the combustion engine to yield the same dynamic performances with reduced consumption, as the part load operation is reduced, among other attractive features, like Stop-and-Go operation, brake energy recovery and power assist. All this features improve the fuel economy without drawbacks in terms of driving comfort, as long as an appropriate energy management is used. As if it were not enough, also exhaust pollution abatement can be achieved by a sensible choice of the engine and generator operating points during warm-up operation, especially as a result of a decreased light-off time of a catalytic converter by requesting an additional torque during thecold start phase of an emission cycl.