[Half-Inch Stud]

Opinions on the Steel Slugs out there for gasoline engines?
Not just for Diesels anymore.

Features:
Super-high Top ring, tight ring stack
Super-high Pin bore, so Skirts can be super-short.
super-short Pin length.
Overall Much Lighter than Aluminum slugs.

Drawback: must have underside squirt for cooling the slug center. Likely need oil-coolant heat exchanger before air-cooled coolant radiator.

http://www.cycleworld.com/2016/01/14...ology-feature/

I say "Wow" Go

...I'm not talking 60's PMD cast aluminum with steel inner.

[mgarblik]

Seeing lots of new developments in piston designs. Steel is becoming popular in light duty high revving diesel engines from Fiat and MB. Haven't really seen any in use in gasoline production engines yet, but wouldn't be surprised based on the advantages you listed above. If your really into pistons, design and materials, check out this link to a NASA study done 22 years ago on a carbon/carbon composite piston for gasoline engines. Anything to decrease weight, piston to wall friction, and maintain oil control is being looked at very carefully now with the new EPA standards and mileage standards. Up to 60% of engine internal friction comes from piston to wall friction. Lots of room to improve there.
http://ntrs.nasa.gov/archive/nasa/ca...9940031440.pdf

[Half-Inch Stud]

mgarblik, Excellent Ref find. just too bad their piston design sucks. The HP TQ plots would look quite different/better if the slug was design with the Features gained, then the recipro mass saved put into the flywheel.

Yes familiar with carbon-carbon for reentry vehicles. I need to compare its Thermal conductivity with steel to see if features vs drawbacks are the same.

[Craig Hendrickson]

Fascinating info at the links. Certainly they're high on the technical scale. H.I.S. and mgarblik thanks for posting.

[Elarson]

I like the idea of having an open mind toward other materials.

But I'm skeptical of the extremely short skirts on the steel piston shown in the article. I think piston stability and ring seal would be pretty sketchy.

Eric

[77 TRASHCAN]

Smokey Yunick spoke often in his Circle Track magazine columns about the potential benefits of a steel piston...if someone could make one light enough. I'm surprised he didn't try to make some, he experimented w/ many other engine parts.

Yeah that skirt looks way to short...but we're all used to aluminum pistons, and the engineering that makes them function...

[Half-Inch Stud]

Originally Posted by Elarson

I like the idea of having an open mind toward other materials.

But I'm skeptical of the extremely short skirts on the steel piston shown in the article. I think piston stability and ring seal would be pretty sketchy.

Eric

Stability greatly improved with pin sooo high up, allows the skirts to be fashionably short. Daisy Duke short.

Make me wonder about the Stability Rules for Pin-height to Skirt extent for Steel vs Aluminum Skirts. I seem to thing the aluminum skirts were a significant heat dump into the CYL wall (Inhale dominant, then rings being second, skirts, then Pin & Rod as the last thermal path).

[BruceWilkie]

High ring pack not desirable IMO especially with power adder.

[BruceWilkie]

I think composite plastics combined with powdered metals technology has possibilities.

[Half-Inch Stud]

Sooooo, i hear Steel Pistons are making an application in a Diesel. Lighter than the aluminum slug.

[Jack Gifford]

Originally Posted by Half-Inch Stud

... Overall Much Lighter than Aluminum slugs...

Nothing in that article claims "much lighter" than aluminum alloy. The real advantages lie elsewhere- longer fatigue life, less strength loss with temperature, better ring land precision under stress, etc.
I've had that piston photo on the garage wall for about a year now. The testing environment (motorcycle racing) certainly is severe enough to validate the results.