cr vs octane

Crazy_Canuck

does anyone know what Dynamic compression ratio works best at what octane rating? does desktop dyno 2000 calculate based on static or dynamic compression? i have heard that octane requirements at 180f are 3pts lower than at 210f ie 210f+7.5 DCR=91octane 180f+7.5 DCR=89octane(what id like to run) (from my understanding of thermal dynamics it makes sense, as well as cold air intake for insurance)(these numbers are from a graph i found but i think cast heads would be different) if i had substatial cooling 3-4 core aluminum radiator + larger motor oil cooler would i be able to run 7.5 DCR on 89 octane on a 360? more compression or less, what would the limit be on 87?

SwampRat

Desktop dyno calculates static compression ratio, not being an engineer and formula wiz I think it's near imposssible to truly calculate running dynamic compression ratio. True dynamic compression factors in the air quality and trapped VE, etc. Effective compression ratio on the other hand just factors in static compression, stroke, rod length, and intake valve closing and can be calculated fairly easy. Another way of interpreting dynamic compression is through cranking compression numbers but of course this still doesn't have much to do with a running engine. "Good" cranking compression numbers for a pump gas street ride are in the 160-180 psi range, and a max of 200 psi usually with electronic engine management.

Here is an effective compression ratio calculator.
http://kb-silvolite.com/calc.php?action=comp2