ceramic pistons - discuss

Gut reaction "Dodgy"

I remember people like Smoky Yunick working on these long long ago. Technology has improved, but there are still some quirks about these things.

I heard it said that ceramics are best used on engines that are used for long times at a set power level, and that the engine needs to be warmed completely before coming up to full operation.

There are some sound principles involved, but the application of these principles has prove difficult. One reference to naked aluminium bores running with no rings, I have to wonder about expansion coefficents :)

Of course, expansion coefficients are an issue. "Naked aluminum bores" may not be totally naked. There is a world of technology out there to make things that are beyond the present horizon.

I have always been interested in "metallizing". This technology is somewhat like electroplating, but the electrolyte bath is usually a fluoride flux. The base metal can be infused with metallic ions via this bath. The new metal actually penetrates and forms a surface alloy with the base metal. The possibilities are infinite.

forgot:

it's impossible to warm an engine "completely" before coming to full operation - think about it.

if it's fluoride, it's much more likely to be an etch rather than "infusion". unplated aluminum bores [example, porsche 928] use a high-silicon aluminum casting, then etch the aluminum from the honed bore surface leaving only silicon crystals in relief [hydrofluoric acid is a common aluminum etchant]. silicon is highly wear resistant and thus provides the working surface.

you probably have more of an issue on expansion ratios between a steel bore and an aluminum piston. on a direct comparison, silicon carbide is an order of magnitude less expansive than aluminum.

Hence the rings. I beleive the ceramic won't expand much under heating but the bore will.It seems to be a fine line they will be working to.

I imagine the ceramic piston will match the bore at operating temp but will be a mismatch when cold.I don't think micron sized wear coating will affect the coefficent of expansion. It's a well known problem with this tech.

there's two types of "ceramic" - ceramic coatings, the ones you're apparently thinking about, and full ceramic, where the whole component is ceramic all the way through. it is the latter that has the benefits of much reduced thermal expansion, lighter weight, and much better heat resistance - per the original cite.

No, I am referring to the items in the OP. A ceramic coated piston would presumably expand at the same rate as the base material. I don't think a solid ceramic piston would expand very much as you say.An aluminium bore even if coated with a ceramic coating woul expand as per aluminiums coefficent leaving the solid ceramic piston with no rings flopping around :)

No, the plasma coating is for wear, and will not affect the c/e appreciably. If it were very thick, it probably could not stand the expansion of the cylinder bore.

With all due regard for German technology, I have long ago lost my trust of everything new and exciting that is offered on the market, and would not be the first to buy a set of these (if I owned a vehicle which might benefit from them).

Agreed, I'll wait until they are fitted from new.