When using new piston rings in an Alusil engine block, it is essential for good ring sealing that the cylinder walls are properly prepared. This requires a fairly involved process in working the Alusil to the surface finish specifications published by the patent holder of the Alusil alloy.
There are many misconceptions about Alusil, one of the most common being that it is a "spray on" or applied coating to the cylinder walls. This is in part due to the confusion with other process such as Nikasil or Lokasil which are in actuality entirely different. Alusil is an alloy of aluminum containing silicon patented by Kolbenschmidt Aluminium-Technologie GmbH. This means that the entire casting in which the cylinders reside is a heterogenous alloy and the entire casting contains the silicon crystals. For this reason, it is very feasable to recondition cylinder walls as the silicon content is present deeper in the walls as well. However, machining and reconditioning the cylinders in an Alusil block requires a significant investment in time and technicique to preserve the integrity of those silicon crystals.
Fast Attack Motorsports is one of the very few shops in the US with the equipment, experience, and technique to perform this process properly and to specification.
While not all bores can be prepared by honing and exposing alone, many can. For those that can not be due to existing cylinder wall condition (i.e. gouges, scrapes,etc), some light boring is done keeping in mind the end goal for diameters and available pistons.
While our experience is rooted in the BMW S85 and S65 engines, the process is applicable to all engines with Alusil blocks such as those manufactured by Mercedes, BMW, Audi, and Porsche.
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