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Increased engine loads, coupled with low friction rings, renew the attention for predicting the maximum bore deformation which a given ring design can conform to before losing contact. The MIT developed “Software of Ring Design Tools” (RDT) code was used to verify the different published ring conformability criteria by progressively increasing the bore deformation until the model predicted lack of contact. For simple order deformations, the semi-empirical Tomanik criterion was found to correlate with the model predictions. However, as expected, more realistic deformations combining different harmonic orders were able to cause lack of conformability, even with the individual order amplitudes being lower than the criterion limit. In search of a more comprehensive criterion, an automated model ran hundreds of thousands of deformation cases in combination with relative ring angular positions looking at conformability.

Numerical characterization of surfaces with deep dimples, e.g. Laser Textured Surfaces, poses questions relative to the standard filtering techniques used to separate roughness, waviness and form effects. Usual roughness filters would produce a reference plane several micrometers “below” the surface. If this surface plane will be used as reference for mixed lubrication modeling, no hydro dynamic pressures and excessive high contact pressures may be calculated. The conventional roughness filters, Gaussian and Rk, and 4 other filters were applied in an artificially dimpled surface in order to demonstrate and especially to discuss how the Greenwood contact parameters were affected. Depending on the filter used, the estimation of the minimum surface separation for asperity contact varied two magnitude orders.

Low viscosity combined with appropriated additive technology is one of the main paths to reduce friction on Internal Combustion Engines. Japan is on the cutting edge of low viscosity oils, having already available SAE 0W-8 in the market. On the other hands, in emergent countries like Brazil, SAE 15W-40 is still used in some passenger cars while the Japanese origin car brands use SAE 0W-20. Lubricant friction additives type also differs depending on the original equipment manufacturer (OEM) origin, and the Japanese ones usually containing high amounts of the Molybdenum type. In this paper, some of the advantages and challenges of using low viscosity oils are discussed and emphasis is given in the friction reduction obtained with the synergic effects of the right choice of additives components type and the material/coating used in the engine parts. Ring-liner rig and floating liner engine tests comparing different oils will be presented.

Five automotive oils, with different viscosity grades, were tested under different loads and speeds in a reciprocating test using piston rings and cylinder liners. Starved and fully-flooded conditions were also considered in order to analyze the influence of lubricant supplier in the lubrication regimes, especially in boundary-mixed transition. The expected Stribeck curve behavior was observed, and more interesting visualization appeared when the viscosity value was extracted from the Stribeck abscissa axis. The higher viscosity oils showed lower friction coefficient at low speed/load ratios. Such behavior is usually neglected and may be significant to understand the triblogical behaviour of engineering components. Computer simulation showed similar results, including the “cross-over” speed/load when the lower viscosity oils start to show lower friction.

Motivated by the demand for the reduction of fuel consumption, in particular to meet the engine energy efficiency goals of the Brazilian incentives legislation (INOVAR AUTO), this paper proposes a method to identify potential for energy efficiency and exemplifies it through three engines of the Brazilian market. The proposed method consists in identify the engine losses in different operating points (speed x load) through combustion mapping and the basic formulations which describe the energy/losses share. These data are grouped into 12 map sections, allowing the identification of the ones with more improvement potential. The baseline engine is 1.6 l naturally aspirated, port injection and was tested with E100 fuel (100% Ethanol). Engine #2 is similar to the baseline but with 4 valves per cylinder and a lower viscosity oil. The engine #3 is a more advanced engine: turbo charged, direct fuel injection, variable valve train and piloted pumps.

Some different equations to calculate the maximum deformation that a given ring can conform to, are found in the bibliography. These equations do not consider the ring end gap and ovality, gas pressure acting on it, nor the actual bore shape, but only the maximum amplitude for a given term (from a Fourier Series that describes the bore shape). A more exact prediction can be done with Finite Element tools or specific codes for piston ring simulation; those approaches are not usually carried out, except in special cases or in more fundamental studies. Experimental measurements were carried out to verify the simple conformability criteria. Deformed shapes were produced in a static jig and areas of “non contact”, between ring and the deformed bore shapes, were measured. Based on these measurements, a semi-empirical equation is proposed to calculate the limit of piston ring conformability.

In the last years, sophisticated analyses and control of topography parameters have been introduced to study engine bore cylinders. Such surface characteristics have impact on friction and wear of the engine, with effects on fuel consumption and durability. Among such characteristics, folded metal blocking the honing grooves has received much attention, but its quantification and actual impact on engine performance is still under discussion, both in the academia and in the industry. In this work, a methodology was developed to mathematically quantify the folded metal present in engine bores. The method is compared to others described in the literature and in use by some European automotive manufacturers. The quantification method, based on topography measurements, was also compared with other analyses, such as optical and scanning electron microscopy. The necessary resolution of the topography measurement and some recommendations for the analysis are given.