Quote:
Originally posted by john70t
The alusil sounds like it has two good properties in its formula: aluminum base material that transmits heat well, and a good spattering of sand crystals which act as an ultra-hard wear surface.
Some questions:
-do the cylinder materials wear from top to bottom in a good, repairable shape with outwards pressure , or does it even matter with fresh rings ?
-do alusil cyls need to be used with a specific piston that matches its (AL) expansion rate, and what are the o.k. range specs?
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Just trying to learn here...and I think these are all damned good questions. I also recently read an article in a domestic car magazine...okay, it was HOT ROD, that explained some of the differences between domestic V-8 cast pistons, forged, and hypereutectic pistons. Forged, it seems, are the strongest, but they need to be "slappers" when cold because of their high expansion rate. Hypereutectic, developed by Keith Black for use in the old "slingshot" dragsters, are nearly as strong as forged, yet allow for much closer engine assembly tolerances because the have such a low expansion rate. A local mechanic, who does engine rebuilds for the local dirt trackers informed me that most of the alcohol burning "outlaw" engines here have KB hypereutectic pistons in them. So...does anybody make hypereutectic pistons for the 911? If so, how have they worked out? In a normally aspirated engine, I would think this compound could offer some advantages over forged???