Nicasil plating of (steel) cylinder bores...

[Greg Hermann]

>Hi
>
>With all this talk of the vega engines I came to think about the technology
>used on dirtbike engines. An aluminum bore plated with nicasil, whatever
>that is, it was many years since I played with bikes. Can that be done to a
>steel bore, I remember that is was supposed to make the heat transfer better
>or maybe that was because of the aluminum bore.

There are several bore coating technologies--mostly for aluminium.

Nicasil is one,

Chromal is another-- Porsche used it, successfully, it is hard chrome on
aluminium.

There is one I do not know the name for, OMC used it when they were playing
with Wankel outboards,  Somehow they were plating tungsten carbide onto
aluminium.

I have heard of one Porsche used which they called Biral--don't know if
this is synonomous with nikasil or not.

The Vega engine did NOT use a coating--they used a hypereutectic aluminium
alloy in which silicon particles precipitate out as it solidifies. Then,
they etched the bore surfaces, so as to leave only the surface of the
silicon particles as the wear surface. It definitely did NOT work as
planned!

As for cast iron--Bore Tech is the only one I know of, they do a carbide
conversion of some sort to the surface of the cast iron. Makes it harder
than a lady of the evening's heart.

Greg



>
>I know that there was almost no wear on the bores, I think that I have the
>25th set of piston and rings or so in my old dirt bike and it has never had
>any work done to the cylinder bore. There is (was?) a place here in sweden
>that could apply a new plating if the bore had to be machined to an over
>dimension. I also remember that some place fitted steel bores in the
>cylinders and if you used that aproach different piston rings had to used
>and all of a sudden you also had cylinder wear.
>
>I had a KTM 4 stroke dirt bike that also had nicasil plating and that bike
>had no measured wear after 20000+ miles. That includes the piston!
>
>Jörgen Karlsson
>Gothenburg, Sweden.
>
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