The influence of gear step selection on a passenger car fuel consumption 2022-36-0046

Several factors interfere with vehicle fuel consumption. Among them, the relationship between the transmission and the engine, defined as matching, stands out. This paper seeks to analyze the impact of varying the gear step values and, consequently, the intermediate gear ratios on a passenger vehicle's fuel consumption. The vehicle chosen for this analysis was the 2018 Toyota Camry, which has a A25A-FKS "Dynamic Force" engine model with 2.5 liters and 4-cylinders, operating under an Atkinson cycle. The transmission chosen is the UB80E model, which is originally used in this vehicle. It consists of an automatic transmission with 8 gears, coupled to the engine by a Trilok converter. Performance data and brake specific fuel consumption values for this engine were obtained from researches carried out by the U.S. Environmental Protection Agency (EPA). For relating gear step selection influence on the vehicle fuel consumption considering two different driving scenarios, a mathematical model was developed using MATLAB software. In this model, the transmission ratios of the first and eighth gears are kept constant, varying only the intermediate gear's transmission ratio values. Using vehicle velocity and accelerations as model inputs, engine speed and torque are calculated to obtain specific brake fuel consumption values for each one of the intermediate gears. In possession of these values, through optimization, the transmissions that provided the lowest fuel consumption for each driving scenario are obtained. The chosen driving cycles are described in NBR 6601:2000 and NBR 7024:2001 standards and approach road and urban scenarios respectively.