Bluesnailman said:hypereuthetic....
Not a word I knew, but it's on here and it's on Wikipedia so must be true. All to do with the quantity of silicon that limits thermal expansion. Every day a learning day!
Yep, they do not expand as much allowing for tighter cylinder wall to piston clearances thus making more power and are harder than normal cast pistons therefore surviving more abuse, but not great with detonation because of being harder makes them more brittle. That’s why correct timing and mixture is so important
Abel