Guys, sorry if this has been covered before but I can't seem to find what I'm looking for by searching.

I was looking for some calculators for DCR on a boosted motor, if they exist. More than that, I'm looking for some idea of where sanity is at when I get the number calculated. About the only thing I've found so far is this chart of static compression vs. boost for a roots-blown motor on Holley's tech website. They recommend keeping the "effective" compression ratio below 12:1 on this chart (look about 1/3 of the way down):

http://www.holley.com/data/TechServi...ech%20Info.pdf

That's nice, it gets me in the ballpark and it roughly lines up with my growing experience with roots-blown engines but I was wondering about a DCR calculation as well to help me expand my understanding.

In this case I'm talking about a carbureted roots blower application, no intercooler on pump gas. Namely, I'd like to know how to calculate it and where I start to push the limits of safety/longevity. Believe me, I've already found ROUGHLY where the limits are, but blowing up motors is an expensive way to learn!