Ring seating, heat transfer

[oldjohnno]

I run a small (350cc) single cylinder two stroke LSR bike, making about 4hp/inch N/A in which is quite mild for a two stroke but still enough to make piston temp something to watch closely. You can get a pretty good idea of maximum piston temps from the baked oil color on the underside of the piston crown though of course you can't put an absolute number on it. It'll survive sustained WOT and load indefinitely if everything is right but if it isn't it'll melt the piston in seconds. I did some lengthy dyno testing comparing a single ring with two rings and couldn't find any evidence of a change in piston temps. Whether this is relevant at all to four-strokes (two-strokes are largely fuel-cooled) I don't know but I was a little surprised that there was virtually no change at all with a single ring.

[hoodeng]

What is the criteria for your understanding of ring seating/seal.
How do YOU know rings are seated?

If bore geometry is correct and the rings are a known quantity ,the "presumption" of seal is taken before starting, cylinder leakage and comp test also augment our predictions,,,all of these are static or slow rpm tests though.

The real test of seal is dynamic ,that is, measured blow by @ load, we can get a leakage gauging with a manometer on a multi cylinder engine.
On Pro Stock V twin engines with a Dailey pump we used to see 22" of pan vac, if the vac tapered down the data during a pass it indicated ring seal issues.

https://www.sbmar.com/articles/measurin ... condition/

Cheers.