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WE do not have hyper-eutetic pistons.....I cannot stress this enough. We have eutetic pistons which are not the same. Eutetic is a name give to a cast alloy which relates to the type of melting point the alloy has.
A Eutetic alloy has a sharp melting point, that is, its melts at a given temperature and not a temperature range.
A Non-eutetic alloy does not have a sharp melting range and therefore has a plastic melting range, meaning as temp rises the alloy will begin to become weak till it evenually begins to melt.
A hyper-eutetic alloy is a eutetic alloy that has a melting point above the normal range for that alloy. In piston cases the allow is Aluminum.
Now lets apply this knowledge. Pistons are typically made up of Aluminum, Copper, gold, silver, manganese, nickle and silicon, prolly a few other substitutes. Now soft metals like Gold and Copper have no eutetic point because they are not eutetic metals. The aluminum alloy (conbined with sold metals to form the allow chosen) is combine with a percentage of Silicon. We know this because the amount of silicon determines the rate of heat expansion in our pistons. Typical content of silicon is under 20%. At 25% or more the piston greatly loses strength. The more Silicon a piston has, the less expansion the piston will have when heated. This is because Silicon expands less than aluminum. However, the more silicon you have the weaker the piston. At a melting point of a eutetic alloy, 12% silicon is all that will melt, the excess percentage will maintain a granular form in the melted alloy. The Reduction of Silicon is one way to create a Hyper-Eutetic piston. However, its not that simple, the alloy has a lot to do with it and silicon is not just there to regulate the Eutetic point of an alloy, the rate of expansion when heated becomes an issue which is why hyper-eutetic pistons are not good boosted application pistons. Dont over simplify the concept, alloy contents cant become pretty complex. If you add too much of a non eutetic allow such as Copper to an alum alloy, you will lower the eutetic value due to the non-eutetic properties of the combined alloy.
I dont want to try and go into chemical formulas and shit I really dont understand fully, thats just a small explanation of what Hyper-Eutetic is and Eutetic means. Our pistons are NOT HYPER-EUTETIC.
Its well know by engine builders that Hyper-Eutetics are not too hot for boosted applications anyway.
Hope this explains it a little, I am not the hottest at explainations.
Terry
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