It will only be a short time now that oil prices have hit $140's until cellulosic ethanol fuels will be commercialized. The economic stimulus is in place and market forces are at work. However, there are no engines in cars today that can take advantage of the high anti-knock rating of E-85 (85% ethanol, 15%gasoline). If the economic incentives remain in place, E-85 optimized engines may start to appear, but car makers may resist this change, as they usually do.

The basic factor in optimizing an engine for E-85 is the compression ratio. For gasoline engines, compression ratios greater than about 10.5 are not feasible, because gasoline pre-ignites and causes knocking and engine damage. Modern engines have acoustic control systems that pick up the noise from the knocking and change ignition timing and other factors to eliminate the knocking. Control of knocking problems in our gasoline engines results in an upper limit for thermal efficiency (ratio of work output calories to fuel input calories from the fuel). In current engines with 87 RON gasoline, this efficiency is about 25%. This is a limiting factor for fuel economy for gasoline-fueled engines.

E-85 ethanol fuel has a knock rating of about 103 RON. It will not knock (pre-ignite) until compression ratios are over 13:1. If an engine is optimized for E-85, with a high compression ratio and some other changes, the thermal efficiency will increase to about 33%. This increase in thermal efficiency will boost fuel economy, probably to exceed fuel economy of gasoline fuels. E-85 optimized engines will benefit from a high compression ratio, just as Diesel engines benefit from high compression ratios.

In Minnesota, we have many E-85 outlets, so an engine with highe compression ratio could be fueled with E-85 exclusively and never have to use gasoline. I am ready to make that change, as are many others in our state, but there are no engines available that are optimized for E-85 and the gasoline-optimized engines give poor fuel economy when using E-85. The Flex Fuel Vehicle engines are really gasoline engines with modified fuel systems to tolerate high percentage ethanol fuels. We tax payers are rewarding the auto makers with cash incentives to make the few simple modifications required for the FFV designation. I think the incentive is $2500 to $3500 per vehicle (I do not have any new data on this, so please correct my info). FFV's give lower fuel economy when using E-85. Curiously, the fuel cost remains about the same for gasoline or E-85, when E-85 should give greater fuel economy, if used in a high compression ratio engine.

I think we can see where the improvement is needed, but we do not hear about any changes from engine manufacturers. Imaging that Ford, GM and Chrysler would make some of their vehicles with alcohol-optimized engines, which I, for one would immediately buy, these companies would have something to export to Brazil and other countries where alcohol fuels are readily available. In time, these alcohol fuels, especially cellulosic ethanol, can replace a large fraction of the transportation fuels required and we will not be dependent on foreign oil, as we now are. Another most important benefit of alcohol fuels, especially cellulosic ethanol, is much lower carbon dioxide from combustion processes in engines, resulting in lowering Greenhouse gas emissions in our nation.

From: Richard Griffith
An Independent Energy Consultant
952-941-3738