how do gas ports affect cylinder filling?

[Roundybout]

Where is ring flutter more prevelant in the 4-strokes of operation? I would imagine during the expansion/power stroke the ring is held tight by the pressure and to some extent during the compression and exhaust stroke. The intake stroke has no pressure to speak of and believe that's where most of the problem with sealing and ring control leading to charge contamination is. Or is it everywhere and random once control is lost, especially when the piston nears the bottom of the stroke where pressures tend to be lowest?

[ptuomov]

Where is ring flutter more prevelant in the 4-strokes of operation? I would imagine during the expansion/power stroke the ring is held tight by the pressure and to some extent during the compression and exhaust stroke. The intake stroke has no pressure to speak of and believe that's where most of the problem with sealing and ring control leading to charge contamination is. Or is it everywhere and random once control is lost, especially when the piston nears the bottom of the stroke where pressures tend to be lowest?

There's the question of ring seal at each point of the cycle and then the question of whether you care about ring seal at that point of the cycle. The nice thing about piston rings is that any time there's a pressure differential they automatically seal as long as there's no "gas ports" which make the seal one-sided.

To me, the main question is the inertia of the ring sometimes overcoming the pressure differential force. Ring width (and material density) are what determines that for given inertial force and pressure differential force.

I am just thinking out loud, so experts please correct me.

[Roundybout]

Where is ring flutter more prevelant in the 4-strokes of operation? I would imagine during the expansion/power stroke the ring is held tight by the pressure and to some extent during the compression and exhaust stroke. The intake stroke has no pressure to speak of and believe that's where most of the problem with sealing and ring control leading to charge contamination is. Or is it everywhere and random once control is lost, especially when the piston nears the bottom of the stroke where pressures tend to be lowest?

There's the question of ring seal at each point of the cycle and then the question of whether you care about ring seal at that point of the cycle. The nice thing about piston rings is that any time there's a pressure differential they automatically seal as long as there's no "gas ports" which make the seal one-sided.

To me, the main question is the inertia of the ring sometimes overcoming the pressure differential force. Ring width (and material density) are what determines that for given inertial force and pressure differential force.

I am just thinking out loud, so experts please correct me.

That's along my line of thinking. My important ones would be expansion and intake. If your losing something during the compression stroke besides power it's only going one way, into the crankcase. Ditto for the exhaust. Now I'm thinking about a vacuum pumps and how gas ports interact there. I'd imagine that helps my bottom of the stroke theory and why they work among other reasons.