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1 Commercial vehicles have been more and more equipped with more powerful engines allowing considerable increase in size and load capacity. With this increase in capacity, it becomes important to evaluate the efficiency of the brake system to ensure vehicle safety during transportation of people and materials. Braking efficiency of a vehicle is significantly affected by the heat generated by friction between stationary components and rotors. This heat raises the temperature of the components in brake assembly reducing the friction coefficient at the interface between brake lining and drum. Once the friction coefficient is reduced, the braking torque decreases. As consequence, it may cause undesirable scenarios such as braking performance loss due to overheating, tire burst, hub grease melting, brake lining failure, thermal cracking, geometric distortions and brake locking.

The new engine demands performance increasing, fuel consumption, exhaust-gas and noise emissions turn to diesel in special automakers. The way to improve fuel economy and thus the emition of less CO2 in diesel engines is an environmental challenge key for reducing emissions of nitrogen oxides (NOx) and particular matters. Market demands have resulted in development of high-performance fuel-injection system with higher pressure injection that better atomize fuel and precisely control injection timing and quantity. The valvetrain designers are faced with new requirements to achieve the new limits. The latest Tier II U.S. emissions regulations are being phased in between 2004 and 2007, when 100% of new registrations will have to comply. The multibody system dynamics based on the classical mechanics treated by Newton, Euler, D'Alembert and Lagrange and high developed in the last 15 years by Kortüm, Schiehlen and Huston.

The work described in this paper performs the modelling and simulation of a Canadian Jeep named Iltis using Multibody Systems modelling techniques. This vehicle is of military use in Canada and the data was provided by Prof. R.J. Anderson as part of the IAVSD road vehicle benchmarks. The equations of motion were obtained using the MBS equation generator SD/FAST. The simulation was performed with the general purpose simulation program ACSL. Analysis and pre and post processing was carried out with the matrix analysis package MATLAB. The paper discusses aspects related to computational performance of the equation generator and the simulation code. It also discusses vehicle behaviour as it performs various maneuvres. Quantities presented are equation complexity and cpu usage for the equation generation phase. Runtime is used to characterise simulation code performance.