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The growing use of tribotest has been helping the researches to understand the actuation mechanisms of additives on the friction and wear control of engine parts. But, it is common to observe differences between the tribofilms formed in real situation from that obtained using tribotests. Furthermore, the automakers have difficulty to correlate the results obtained using tribotests with that performed using engines in dynamometers. For the piston ring/cylinder bore tribosystem is almost impossible to reproduce its real tribosystem using tribotests. Therefore simplifications are necessary and they affect the tribochemical behavior of the tribosystem. To understand how these simplifications and the test parameters affect the tribochemical behavior of the simplified tribosystem is critical to design a tribotest that correlate well with the real situation.

The automotive electrical fuel pumps for gasoline and alcohol fueled vehicles engines are lubricated by the fuel itself. The new flexible fuel engine technology, specially in Brazil, the fuel pump is designed to be lubricated by gasohol (E22) or strait hydrated ethanol fuel but it is also exposed to the variable gasoline/alcohol blends in the flex-fuel engines. This paper presents the influence of different fuel blends, ethanol and gasohol, to the fuel pump wear and corrosion behaviors. The tested fuel pumps were designed for gasohol only engines. The fuel pumps were tested in a bench device, which simulates the vehicle fuel circuit, using gasohol (E22), hydrated ethanol (E100) or 60 % in volume ethanol-gasoline mixture (E60). The scanning electron microscopy examinations and roughness measurements were performed for tribological analysis of fuel pump gears. The observed wear and/or other deterioration mechanisms were mainly due to the abrasion and corrosion.

Two electrical fuel pumps were performed with different fuels in two different vehicles. The pumps accumulated 60.000 km and 190.000 km in passenger cars. Both vehicles and pumps were designed to operate exclusively with gasohol (E22), one of the pumps was tested with 60% ethanol in volume of gasoline blend (E60) for 60.000 km from June-2001 to February-2004. The other pump was tested with gasohol (E22) for 190.000 km from August 2000 to February-2004. The test conditions represented the actual use of the vehicles. Such test is not common vehicle manufacturers practice application because it requires a considered long period of time for evaluation procedure. This test helps both the analysis of soak time influence and the running time. This paper presents a tribological analysis of the components in order to compare the influence of both fuels on wear mechanisms or other degradation that could be influenced by the non usual E60 fuel.

A ring on block lubricated sliding wear test was used to study severe adhesive wear or scuffing between cam and cam-follower materials. The scuffing resistance was measured at constant 4,85 m/s disk velocity. DIN 100Cr6 quenched and tempered rings were tested against DIN 16MnCr5 blocks treated to obtain two different surface conditions: a) carburized;, b) carburized and nitrocarburized with predominantly carbonitride layer. The worn surfaces were characterized using scanning electronic microscopy (SEM). The phases present at the nitrocarburized layer were characterized using GDS. The role of the layer on the scuffing resistance was evaluated. The nitrocarburized specimens had better scuffing resistance than carburized one. The friction power intensity criterion was used to define the capacity of the material to resist to scuffing. A low FPI (friction power intensity) has a high scuffing resistance.

Since wear is a not a material property, but a tribological system property, it is of great importance to know the wear, friction and lubrication behavior of materials tested in bench equipment. This work presents reciprocating pin-on-plate bench tests results, with gas nitrided stainless steel pins and gray cast iron plates. The testing conditions were 0.5 and 3.2 Hz frequency, 20 and 600N applied load and 100 and 150 °C. Under these conditions, mild to severe wear transition was observed. It was noticed noise emission changes at wear transition. This noise change could be used to verify wear transition mechanism.