Dynamic compression

I just built a new motor and will be running E85 as I have been for the past 4 or 5 years. Just curious, but what is the max dynamic compression that can be ran with 93 octane? Is there something out that shows a given dynamic compression and the octane required?

I don't know that I'd take it as The Final Answer, but I suppose it may give you some idea of what may be possible.

EDIT: This is from David Vizard
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IMHO DCR over-rated as a limit. With enough gear and stall speed, it almost doesn't matter.

There are enough people way smarter than I am who have beaten this subject into the ground on SpeedTalk that I don't even take it into account for my own builds.

Even if it is a valid predictor of fuel octane requirements (and that has been a key issue in the ST debates from years back), you can't even get two people to agree on what valve- or cam-lift measurement establishes the IVC point.

The IVC point will matter at different RPMs, what I mean by that is inertia supercharging will affect it more or less as the RPM changes.

The chart above is ok to give you just an idea but will be different with different engine combos with quench or without, port desighn, how cod the intake air is or is not, runner length, reverse flow or standard cooling... many other things but strictly temperature speaking gives you a rough idea how it will be effected just by coolant temp.

For the most part polys statement is true, especialy with ethanol as it seems people are running very high static and dynamic compression with it and I never heard anyone with detonation issues. I have heard of at least one guy running 16.5 on e85 but I imagine the %15 gas was not ordinary 85 octane like the e85 at the pump.

I don't think low dynamic compression can be used as a reason to run low octane fuel UNLESS you are going to keep the engine speed low.

As soon as the engine comes up on the cam then the DCR goes out the window and you are running on actual compression ratio. That is why race engines with huge cams still need to run race gas. They might not need race gas when driving around in the pits but they need it as soon as they go WOT down the track.

Right, and right.

I've seen three different intake closing points used for the same formula.

My fairly light 383 Dart with a much higher CR, 3.91 gear, and 4 speed got by much better on pump gas than my heavy weight, lower CR Charger with 3.23s, std converter, and no part throttle kick down.