It seems I finally found the document that measures thermodynamic efficiency and octane of Ethanol blended fuels and at various compression ratios albeit with three nonstandard ratios. I only wish they had chosen standard and more Static compression ratios such as 10:1 11:1 and 12:1 including one-half points in between. But the study does fix E50 and E85 at certain octane points. I'm not surprised that 85% Ethanol is closer to 95 Octane but that is at Stoichmetric. With Alcohol can simply add more fuel to eliminate knock. Gasoline you need to remove ignition timing AND run pig rich under high load to keep even a respectable level of Static compression ratio.
http://delphi.com/pdf/techpapers/2010-01-0619.pdf
If you have anything to add or comment on please do so but please no politics!
A couple notes regarding this: this document is highly technical, nerdy and funded by the DOE which is gov't funded so put on your tinfoil hats! /endjoke The reason that RF(reformulated ethanol free) Gasoline, HO(high octane) Gasoline, and even 10% Ethanol Gasohol blends were not fully operational at higher than 9.2:1 Static Compression at WOT and other conditions was that the researchers kept the fuel mixture at Stoichometric for the study and that limits the operational range for the fuels. The only variable was ignition advance and as you will notice the E50 and E85 fuels have differing spark advances. They should have used a ratio between 9.2:1 and 11.8:1 for a better example of Gasoline. Please be sure to at least read some of the opening statements before getting too far into the charts and graph results it is a very technical document.
I also want to add:
You may or may not know that EFI Gasoline engines are set to Stoich for cruise speed and light to moderate loads but will change over above 70% load to fuel enrichment mode or Open Loop. This also explains the abnormally high efficiency of the fuels in this study. On my various Forum lurkings I've found that regular cars like the Honda Fit for example; which runs on the lowest octane grade Regular 87(85 at elevations), enters open loop at 70% load and run at almost 11:1 Air:Fuel Ratio in open loop. Generally Peak power for Gasoline is at slightly rich AFRs like 12.5-13:1 while peak TDE is at slightly lean such as 16-18:1. Stoichmetric is the least polluting ratio and (luckily) is a balance between most efficient and most powerful which is why EFI Gasoline engines operates at Stoich throughout most of their operational range excluding Idle.
Aside: This paper was published by the SAE and it was funded by the Department of Energy. I have some respect for the SAE as an organization but I wouldn't and don't know of any bias on their part. They are not a political organization in my humble opinion.
On another note the SAE has done several Ethanol related studies over the last 20 years that the DOE has been funding research on Alcohols as a fuel source.
I'm excited to finally find this document. As you may know anything E85 related from a scientific standpoint is almost nonexistent especially regarding practical matters such as static/dynamic compression ratios or even a very simple thing as it's true octane value. These were RF Gasoline mixtures with "dry" Ethanol blended on site not mysterious E85 pulled from a random Gas station during an unknown time of year.
From a technical standpoint Alcohols makes up for their low energy density by having oxygen which makes it much more resistant to knock and capable of tolerating much higher peak static compression ratios and peak cylinder pressures than unleaded Gasoline is capable of handling.
Looking at this it makes me think of the last 50 years of ICE development and how Automakers were working around the problems of low grade but cheap unleaded Gasoline to deliver engines that would keep people satisfied. With Higher octane fuels such as the Alcohols we could have been pushing the ICE to it's thermodynamic limit instead of limiting ourselves to a cheap and inefficient fuel source.