The "effective compression ratio" chart is nonsense.
If you examine the numbers, they're simply (atmospheric pressure + boost pressure) ÷ ATM, then × the static CR.
Example: 8.0:1 CR with 12 psi boost shows 14.5:1 CR on that chart.
Assuming 14.7 for atmospheric pressure:
(14.7 + 12) ÷ 14.7 × 8 = 14.53

What's actually happening?
The effective CR is 12.5:1.
How is that calculated?
Read my article:
http://victorylibrary.com/mopar/blower-engine5.htm

Boffin Emeritus