91 Octane in a 340?

AJ,
Post #34. Nope, do not agree with much of your post. As I have stated before, DCR is useless when trying to determine reqd fuel octane to stay out of detonation. Do not understand why folks use DCR. One reason it is useless is the large number of variables that actually cause det, two of which are heat & A/F mixture.

Back to DCR. Can be the same for two engines, one will detonate, one won't. Why? Because DCR is a calculation that does NOT take into account the amount [ specifically: the weight ] of air drawn into the cylinder which can vary because one engine has a more efficient induction system [ better intake ports ] than another.

Detonation is often just one cyl, maybe a few, but not all cyls.
Just out of curiosity how would you calculate the octane requirement of an engine you build then? I get that Scr and Dcr are just measurements but you have to start with something.