thickness of less than 0.005”) in the turbocharged 3.0 liter 991.2 Carrera and Carrera S engines,30 as well · as in Panamera V6 an

thickness of less than 0.005”) in the turbocharged 3.0 liter 991.2 Carrera and Carrera S engines,30 as well as in Panamera V6 and V8 engines that same year.31 With the Alusil process, the entire engine block is low pressure die cast out of the hypereutectic 17% silicon ALUSIL alloy (AlSi17Cu4Mg). After the block is cast and the cylinder bores are chemically and mechanically activated, the resulting silicon particles varying in size from 20 to 70 µm provide the wear- resistant sliding surface for the piston and ring system. For both Alusil and Lokasil, an acid etching process to remove the aluminum surrounding the silicon particles is no longer used during manufacturing. During the honing process, care is taken to ensure the silicon particles are cut rather than torn from the surface during mechanical activation to ensure an exposure depth of 0.3-0.7 µm. The resulting size, shape, and distribution of these particles produce exposed silicon plateaus and oil retaining valleys to support piston and ring travel.32 The ability of the cylinder bore surface to retain oil is directly related to its scuffing resistance.33 The distribution of the exposed silicon particles in the Al-Si matrix is critical. During normal operation, the exposed silicon particles support the loads applied to the cylinder bore by the pistons and piston rings, with at most a few nanometers per hour of wear. Modern engines with Al-Si bores utilize thinner, lower tension rings that provide improved sealing with lower friction than conventional piston rings. Critically important is the use of barrel-shaped piston ring faces, so as to glide across the surface, as opposed to a scraping action caused by some ring types. Excessive ring tension or incompatible ring types can damage the exposed silicon particles, resulting in a failure of the cylinder sliding surface to support the piston and ring system due to plastic deformation of the aluminum matrix.34 35 Coatings like DLC (diamond like carbon), that when applied on piston rings, can also reduce Al-Si cylinder wear, reduce friction, and improve fuel economy.36 30 MMC All Aluminum Cylinder Block for High Power SI Engines. Toshihiro Takami, et al. Toyota Motor Corp & Toyota Central Research and Development Labs, Inc. SAE Technical Paper Series 2000-01-1231. https://flatsixes.com/cars/porsche-991/makes-porsches-new-3-liter-turbocharged-carrera-engines-special/ 31 https://www.sae.org/news/2016/07/inside-porsches-new-v8-and-v6-powertrains 32 Reconditioning of Aluminum Engine Blocks. MSI Motor Service International. 33 MMC All Aluminum Cylinder Block for High Power SI Engines. Toshihiro Takami, et al. Toyota Motor Corp & Toyota Central Research and Development Labs, Inc. SAE Technical Paper Series 2000-01-1231. 34 MMC All Aluminum Cylinder Block for High Power SI Engines. Toshihiro Takami, et al. Toyota Motor Corp & Toyota Central Research and Development Labs, Inc. SAE Technical Paper Series 2000-01-1231. 35 Nikasil and Alusil. John Goodman. Engine Professional Oct-Dec 2008. 36 Wear of different material pairings for the cylinder liner - piston ring contact. Thomas Wopelka, et al. Industrial Lubrication and Tribology. DOI 10.1108/ILT-07-2017-0218. LN Engineering Technical Library. Copyright ©2019 LN Engineering LLC