Ferrari Power Unit Hardware & Software

[godlameroso]

....I cannot imagine it adds significant weight ....

. . . (and a steel piston 33% as thick as an alloy piston won't be stiff enough to behave properly). . . .

I imagine the piston crown underside must have extensive "ribbing" or perhaps a honeycomb structure to give it "thickness" without weight. This would also increase surface area for heat transfer to the cooling oil.

What about cylinder walls? Wouldn't oil burning be an issue with steel pistons? The ring lands themselves would become hotspots vaporizing some lube? This would be doubly so if they're pushing the thinness on the piston rings themselves.

[PhillipM]

A surface coat of a copper alloy might spread the heat enough there, would also protect against scuffing.

[Zynerji]

The 2019 rules have no such restriction on the use of steel for the piston;

5.16 Materials and construction – General :
5.16.1 Unless explicitly permitted for a specific application, the following materials may not be used anywhere on the power unit :
a) Magnesium based alloys.
b) Metal Matrix Composites (MMC’s).
c) Intermetallic materials.
d) Alloys containing more than 5% by weight of Platinum, Ruthenium, Iridium or Rhenium.
e) Copper based alloys containing more than 2.75% Beryllium.
f) Any other alloy class containing more than 0.25% Beryllium.
g) Tungsten base alloys.
h) Ceramics and ceramic matrix composites.

5.16.2 The restrictions in Article 5.16.1 do not apply to coatings provided the total coating thickness does not exceed 25% of the section thickness of the underlying base material in all axes. In all cases, other than under Article 5.16.3(b), the relevant coating must not exceed 0.8mm. Where the coating is based on Gold, Platinum, Ruthenium, Iridium or Rhenium, the coating thickness must not exceed 0.035mm.

5.16.3 The restrictions in Article 5.16.1(h) do not apply to the following applications :
a) Any component whose primary purpose is for electrical or thermal insulation.
b) Any coating whose primary purpose is for thermal insulation of the outside of the exhaust system.
5.16.4 Magnesium based alloys, where permitted, must be available on a non-exclusive basis and under normal commercial terms to all competitors. Only those alloys covered by ISO16220 or ISO3116 and approved by the FIA may be used.

5.17 Materials and construction – Components :
5.17.1 Pistons must respect Article 5.16. Titanium alloys are not permitted.

With a coating thickness of 0.8mm, wouldn't a severely undersized steel piston be able to have a thick titanium coating applied to make up the rest of the thickness of the part? And i see that Ti alloys are banned, but a pure Ti coating wouldn't be an alloy, correct?

I might even nit pick that the piston itself would be exempt from these rules anyways, as "a) Any component whose primary purpose is for electrical or thermal insulation.", and the pistons primary purpose is to thermally insulate the crank area of the engine from hot exhaust gas...

[subcritical71]

A surface coat of a copper alloy might spread the heat enough there, would also protect against scuffing.

What about a TBC (thermal barrier coating) as used in gas turbine blading? Or would the weight penalty be too high(?)

[gruntguru]

. . . (and a steel piston 33% as thick as an alloy piston won't be stiff enough to behave properly). . . .

I imagine the piston crown underside must have extensive "ribbing" or perhaps a honeycomb structure to give it "thickness" without weight. This would also increase surface area for heat transfer to the cooling oil.

What about cylinder walls? Wouldn't oil burning be an issue with steel pistons? The ring lands themselves would become hotspots vaporizing some lube? This would be doubly so if they're pushing the thinness on the piston rings themselves.

Depends on combustion temperatures. There are a number of factors working in favour of the piston from a thermal perspective: lean mixture, rapid combustion, stratified charge.

Steel is in common use for Diesel pistons - often two piece, with steel crown, lands and pin bosses and aluminium skirt.

[PlatinumZealot]

Incidentally, last week I had the opportunity to get first hand confirmation of a long lasting rumour discussed several times here:
Ferrari engine does have steel pistons, and it's not the only one.
Honda is also using steel pistons from the same source.
They are not 3D printed, but steel is the material used since some time now.

Proof?

[PlatinumZealot]

....I cannot imagine it adds significant weight ....

steel is 3 times the density of aluminium alloy
(and a steel piston 33% as thick as an alloy piston won't be stiff enough to behave properly)

but 'fortunately' for the steel piston the engines are limited to about 12000 rpm - so they can stand steel's extra weight

steel pistons can actually be lighter because you have to add more meat to the aluminum for it to "survive." Depends on the design of course. Life cycle and all that.

[godlameroso]

....I cannot imagine it adds significant weight ....

steel is 3 times the density of aluminium alloy
(and a steel piston 33% as thick as an alloy piston won't be stiff enough to behave properly)

but 'fortunately' for the steel piston the engines are limited to about 12000 rpm - so they can stand steel's extra weight

steel pistons can actually be lighter because you have to add more meat to the aluminum for it to "survive." Depends on the design of course. Life cycle and all that.

Aluminum is stiffer but bulkier than steel, then again metallurgy and materials science has come a long way and I'm sure it's not just chromoly tool steel being used.

[Maritimer]

High cobalt would let you run the piston hotter, cobalt tool steels retain much of their hardness even when red hot.

[PhillipM]

It's not the piston strength that's the issue it's problems with overheating the ring lands and the crown giving sealing/oil issues and combustion instability

[Zynerji]

It's not the piston strength that's the issue it's problems with overheating the ring lands and the crown giving sealing/oil issues and combustion instability

So, it's more about even temperature (no hot spots) than anything else?

[rgava]

Incidentally, last week I had the opportunity to get first hand confirmation of a long lasting rumour discussed several times here:
Ferrari engine does have steel pistons, and it's not the only one.
Honda is also using steel pistons from the same source.
They are not 3D printed, but steel is the material used since some time now.

Proof?

Sorry, but I cannot proof you a conversation held with someone who is working on them.

[PlatinumZealot]

Incidentally, last week I had the opportunity to get first hand confirmation of a long lasting rumour discussed several times here:
Ferrari engine does have steel pistons, and it's not the only one.
Honda is also using steel pistons from the same source.
They are not 3D printed, but steel is the material used since some time now.

Proof?

Sorry, but I cannot proof you a conversation held with someone who is working on them.

Ask him if it is a material innovation or a design feature that let them overcome the inherent problems of steel pistons in petrol fueled engines. There was a paper released on them, and the conclusion was something like "they work, but to get more mileage out of them before they coke up more work is needed"

[PlatinumZealot]

It's not the piston strength that's the issue it's problems with overheating the ring lands and the crown giving sealing/oil issues and combustion instability

I think yes, strength of the surface is also a problem. Thermal degradation. Sometime the surface will show micro-cracks from thermal degradation combined with the stress from high pressures. So a lot of the time you see special coatings and alloys applied for aluminum to make it more resistant to it.

[PhillipM]

For aluminium, yes, but for steel pistons?