A personal-computer-based general simulation package has been developed, aiming at optimal design of the vehicular powertrain system. The powertrain system design in this paper includes the design of the engine and drivetrain system. The package is capable of dynamic simulation of automotive performance under various road-driving conditions, such as standstill acceleration (e.g. 0-->100 kph), standard driving patterns (e.g. FTP75), and etc. The theoretical work is based on the cyclic analysis of thermo-fluid-combustion phenomena inside the engine, plus models derived from the engine dynamics, driveline dynamics and vehicle dynamics. Conditions of starting acceleration from standstill of an example passenger car equipped with a manual transmission, or an automatic gearbox, or even a continuously variable transmission, are simulated to demonstrate the versatility of this package. Finally, a proportional-integral throttle control model, simulating the behaviour of the driver, is also devised aiming to fellow the prescribed transient driving schedule in the driving pattern simulation.