UNDERSTANDING BORE SCORING · IN AL-SI CYLINDER SYSTEMS

UNDERSTANDING BORE SCORING IN AL-SI CYLINDER SYSTEMS Charles Navarro LN Engineering LLC Copyright ©2019 LN Engineering LLC. Abstract The basic requirements for a cylinder lining are as follows: wear resistance for the liner, rings, and pistons, as well as resistance to galling and minimal oil consumption. In the beginning, internal combustion engines favored heavy, dense, thermally stable cast iron engine blocks for their durability in meeting these criteria. Besides being heavier than a modern all-aluminum engine, those made from cast iron provide poor cooling, limited performance, and are nowhere near as efficient or powerful as today’s engines designed to meet tightening emissions and fuel economy requirements.1 As aluminum has four times the thermal conductivity of cast iron or steel, it’s the logical choice to overcome these thermal performance limitations.2 However, Al-Si cylinder systems require special surface preparation and piston coatings, not to mention specific lubrication needs. Balancing these requirements has always been a challenge for engineers, especially when cost is the driving motivator for OEMs when utilizing liner-less cylinder technologies. Innovations built upon an all-aluminum engine designed to maximize efficiency and reduce emissions, coupled with hybrid technologies, will extend the life of the internal combustion engine as we transition to an all-electric future. Keywords: Al-Si Alloys, Hypereutectic Aluminum Alloys, Internal Combustion Engine, Combustion Engine Cylinder Liners, MMC, Lokasil, Alusil, Bore Scoring, All-Aluminum Engine Block, Coatings, Piston, Piston Rings, Heat Transfer, Tribofilm, Boundary Lubrication, Wear Mechanisms, ZDDP, Friction Modifiers 1 Improving Heat Transfer and Reducing Mass In a Gasoline Piston Using Additive Manufacturing. Reyes Belmonte, M. et al. SAE International 2015-01-0505. 2 Reconditioning of Aluminum Blocks. KS Aluminum-Technologie GmbH. LN Engineering Technical Library. Copyright ©2019 LN Engineering LLC