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A mild hybrid powertrain with crankshaft mounted integrated motor generator (IMG) and torque controlled infinitely variable transmission (IVT) has shown clear potential for fuel economy (FE) enhancement. It also makes significant driveability and performance improvements possible which are a condition for customer satisfaction and subsequent marketability. The hybrid powertrain supervisory control strategy presented here uses the energy recovered during braking events for power assist, hence improving FE and driveability compromises. This is achieved by operating the engine at its best brake specific fuel consumption (BSFC) point during steady state conditions without deteriorating the transient response as a result of the comparatively fast IMG torque response. This paper demonstrates the launch manoeuvre and general driveability improvements achieved in simulation with validated models.

The use of variable geometry turbocharging (VGT) as an aid to performance enhancement has been the subject of much interest for use in high-speed, light-duty automotive diesel applications in recent times (4). One of the key benefits anticipated is the improved transient response possible with such a device over the conventional fixed geometry turbine with wastegate. The transient responses of two different types of variable geometry turbocharger have been investigated on a dynamic engine test bed. To demonstrate the effect of the turbocharger on the entire system a series of step changes in engine load at constant engine speed were carried out with the turbocharger and exhaust gas recirculation (EGR) systems under the control of the engine management microprocessor. Results are presented which compare the different performance and emissions characteristics of the devices. Some control issues are discussed with a view to improving the transient response of both types.