FUEL CONSUMPTION REDUCTION BASED ON GEAR RATIOS OPTIMIZATION FOR A MANUAL TRANSMISSION APPLIED TO PASSENGER CARS

Resumo

The gear ratio and shifting strategies strongly influence the vehicle fuel consumption because they affect the powertrain inertia and the engine operation. The literature normally presents gear-shifting strategies based on the engine power and torque map to improve the vehicle acceleration performance. The gear shifting strategies based on fuel economy are complex to be stablished due to large number of factors that can influence the engine behaviour such as the available gear ratios, required acceleration and vehicle speed. In this paper, it was analysed the influence of gear ratios in the vehicle gearbox. The gear ratios were optimized through an algorithm developed to improve the engine fuel consumption in the homologation drive cycles. The simulations were performed using Simulink software where the model based on a conventional 1.0L vehicle was developed. The optimization algorithm elaborated in Matlab finds the minimum of a scalar function of fuel consumption of several variables, starting at an initial estimate of gear ratios. The simulation results were stored in a database to compare them with the results obtained with new gear ratios.