Rocker Decision
aj, nm
another dcr article i do not know if you've seen
Dynamic CR
Yes, I have, wyrm..... Scroll to the bottom and there is the link to the Pat Kelley Calculator that I use, for 90% of the work.
I use the outputs of that Pat Kelley calculator and use them as inputs to the Wallace DCR calculator; the Wallace DCR calculator accounts for altitude effects in its output for both cranking pressures and 'effective DCR'. You can also input turbo/super-charger pressures to see where you get for DCR.
Part of the trick to getting close is to try to account for the effective closing point of the intake valve (discussed in the middle of the page that you linked). For example, I'll subtract 8-10 degrees from advertised duration for a solid cam to account for lash, and put that into the Pat Kelley calculator.
It is not a perfect science. But you have to do something to get in the ballpark with DCR if you want to know what you are going to have. And as an aside, all of this has been worked on and used for at least 90 years; a lot of serious engineering research went into the compression ratio matters in the 1920's and then was expanded when superchargers started being applied in cars and airplane engines by the 1930's.
