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In making our products more attractive, it is becoming increasingly important to balance multiple areas of performance, such as fuel economy, emissions and drivability. Customer expectations and government legislations, to protect global environment, strongly increase the work complexity of auto firms in order to release high quality and eco-friendly vehicles. The balancing between several target is becoming a key factor in the car design: respect current (and anticipate future) emission limits optimization of fuel consumption insure high level of drivability maintain acceptable(or increase) performances sustain acceptable cost, reliability, etc. From recent emissions limitations, engine cold start (at the beginning of driving cycle) plays a major role in the total amount of pollutants. Especially, achievements of HC limitations are a big challenge for vehicles with a conventional spark ignition engine.

This paper demonstrates the development of a full multi-body vehicle model and its use in virtual design and troubleshooting of a vehicle response to throttle input. The multibody model is divided into three main subsystems: the chassis, the driveline and the powertrain subsystems. The chassis system includes a complete representation of both the front and the rear suspensions, both the front and rear subframes, and the vehicle body. The driveline system includes the output shafts from the transmission unit to the tires. The powertrain system includes complete representation of the cranktrain for a V6 combustion engine. Also included in the powertrain is a nonlinear representation of the gearbox where bearing clearances and gear lashes are considered. The cranktrain torque output is linked to the transmission using a torque converter model. The vehicle components are virtually assembled together through different joint types, force elements, and kinematic constraints.