ORIGINAL: w8ye
As stated up above a ways, The ring cannot be steel and ride against a steel liner. The ring is CAST IRON
Jim
If pistonring was made of steel, it will be plated with chrome and the sleeve must be cast iron, mostly in automobile engines. When i replaced the steel ring then i tried to break the old steel ring, the ring was soft.. while the cast iron ring will break easy off..
Cast iron ring are best to run with sleeve of hard steel, cast iron or sleeve in other material with surface of chrome, nickel or nikasil.
ORIGINAL: Dar Zeelon
In ringed engines there is a size spec for this gap, so when the engine runs at its intended working temperature, it must be as closed as possible, but not closed!
In model engines can be between 0.0001 mm to 0.005 mm depent on bore size in model engines.
If you see the light though ring gap when the ring are in the upper part of sleeve, the ring are worned out. If difficult to see the light, all ok.
Jens Eirik