Figuring out Dynamic compression

Abodybomber said

Subscribed....I get it,but I don't get it... The intake valve on the closing ramp,against the actual measurements of mechanical compression,are the two major principles..Correct? Sorry for the intrusion,..Maybe if the o.p. learned as well,it would be mutually beneficial...?

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the static ratio is the actual volume the piston squishes, assumign the cylinder is sealed when it's at bottom dead center. Only that's not how an engine works. So dynamic takes into account the time at which the intake valve closes, actually sealing the cylinder. That's why it's always less than the static ratio. However, the OP asked about pressures. Cylinder pressures are dependant on that valve closing, but also the physics involved with filling the cylinder. The higher the rpm, assuming the port and camshaft work well, the more the cylinder will be filled. So the higher the rpm, the higher the pressure, until the system stalls and volumetric efficiency falls off.