The Effect of Oxide and Tribofilm Formation on the Wear of Cylinder Bores from Flex-Fuel Engines

It is well known that machine lifetime, reliability and performance are strongly related to wear. The wear of cylinder bores can increase blow-by, oil consumption, power losses and emissions. Moreover, it can produce axial wear scratches that can harm hydrodynamic support of piston rings, increasing wear even further. The comprehension of the main factors responsible for wear in cylinder bores is, therefore, indispensable for the increase of the efficiency of engines. Despite the great work reported in literature regarding to the analysis of wear in engine cylinders, the study of the types of oxides and tribofilms formed in the surface of the cylinders remains poor. Therefore, the present work aims to correlate wear of cylinder bores from flex-fuel vehicles with engine operating conditions. Although most publications show that top dead center (TDC) is the region of the cylinder with highest wear rates, the present work shows favorable conditions to the formation of certain oxides and tribofilms capable to minimize wear of TDC, making it even lower that the wear usually experienced by bottom dead center (BDC).