dynamic and corrected are one in the same. so, there are only two CR's that are important.

static is the total swept volume of the cylinder ratioed to the volume left(combustion chamber, head gasket thickness, piston domes/valve reliefs) when the piston is at TDC.

dynamic(corrected) is the volume of the cylinder from when the intake valve closes which is determined by the cam grind, then ratioed to the same remaining volume with the piston at TDC.

To calculate dynamic/corrected, you have to know what the "effective" stroke length becomes from the IVC point. Everything else is the same.

 

Static compression is based on compressing one full sweep of the piston in the cylinder into the combustion chamber. This assumes there is no valves opening or closing during the sweep. A sweep is the full range from BDC to TDC. For example if the cylinder holds a total of 100 units and the combustion chamber holds a total of 10 units and you compressed all 100 units into the combustion chamber the static compression would be 10:1.

Corrected compression takes into consideration that a valve will close at some point during the piston sweep. For example if the valve closes when there is only 90 units of the total 100 units in the cylinder (the piston is already on the up sweep), the compression doesn't start building until that valve closed. In this example the corrected compression would be 9:1 while the static compression would still be 10:1.

Dynamic compression is confusing because of the name. Dynamic compression is refereed to in 2 different ways. The first way is a direct replacement for corrected compression. Dynamic compression=Corrected compression just another name for it.

IMO, Dynamic by definition is something that changes. A corrected compression does not change. It is a math formula based on valve timing to determine a compression ratio. In an engine, Cylinder pressure changes throughout the RPM range. Port design, cam timing, AFR and VE can effect the cylinder pressure. Most noticeable is the "sweet spot" in a cam. This is typically when everything works together at its best and cylinder pressure is high. With that changing cylinder pressure is a changing compression ratio or a Dynamic compression. I have always refereed to it as Dynamic compression or Cylinder pressure.

 

For example if the cylinder and combustion chamber holds a total of 100 units and the combustion chamber holds a total of 10 units and you compressed all 100 units into the combustion chamber the static compression would be 10:1.

 

Springer, thanks for another good information, your calculator is a very good tool in that matter too!

Armin.