Heavily downsized gasoline demonstrator

Abstract

Gasoline engine downsizing is already established as a proven technology to reduce automotive fleet CO2 emissions by as much as 25 %. Further benefits are possible through more aggressive downsizing, however, the trade-off between the CO2 reduction achieved and vehicle drive-ability limits the level of engine downsizing currently adopted.

This paper will present results from a 48 V mild hybrid engine demonstrator, featuring an eSupercharger and belt integrated starter generator.

The original 1.2 litre, 3-cylnder MAHLE downsizing engine has higher BMEP levels than any gasoline engine currently in series production. This engine has now been reconfigured to enable a very high specific power output to be achieved, in excess of 160 kW/litre, whilst retaining excellent drivability and fuel economy. Of key importance is a cost effective, efficient and flexible boosting system. An eSupercharger, operating at 48 V, enables the transient response and low speed torque to be more than recovered, enabling both very high specific output and specific torque characteristic with excellent transient response and drivability characteristics.

In this application the eSupercharger is no longer simply a transient device, but also a key contributor to the steady state engine performance. It is therefore essential to the concept that there is a means for supplying the eSupercharger with sustained electrical power, if the steady-state torque output of the engine is to be maintained. The demonstrator vehicle features a 48 V belt integrated starter alternator (BiSG) and an advanced lead carbon battery pack.

This paper demonstrates eSupercharging as a technology enabler for extreme engine downsizing, and discusses the compatibility with 48 V micro-hybridisation, for further CO2 emissions reduction. The energy management, and power flow, for controlling battery state of charge, minimising CO2 and maintaining good transient response will be presented.