fuel economy using biofuels
It is a scientific fact that alcohol fuels have lower energy content per volume (energy density) than fossil fuels. Having been directly involved in the development of the first flexfuel systems for an auto manufacturer, we had to accommodate this fact all the time. The fuel tank reserve, range, injector flow rates, calibration tables, and more - all had to change depending on the percent ethanol or methanol. At first an expensive sensor was used to tell us the alcohol percent, and then later we figured out how to use the onboard diagnostics to replace the sensor. Point is, you have to adjust for the energy density of the alcohol. Now, one advantage of alcohol is the ability to run higher compression ratios and to optimize for fuel economy and emissions.... but you can't easily change compression ratio dynamically - that needs to be built in to the engine design. With an engine optimized for 85% methanol (pure methanol: 65% energy content of Gasoline) we got amazing fuel economy, emissions, and performance results... a case for dedicated M85 - and it would be similar for E85. So, technically, the energy density can be overcome by a vehicle designed for a dedicated ethanol or methanol fuel blend, but the commercial success of that is more determined by fuel distribution, politics, costing etc issues - well beyond the vehicle design. Having said that, what most don't realize is that the 'flexfuel' vehicles on the road today can and do optimize even for the 10% that is in the regular blend, but how much benefit that is needs to be evaluated. For that, and to answer the question about the comparative benefits of M85 and E85 blends versus petroleum gasoline, a thorough lifecycle emissions, fuel economy, and cost analysis needs to be done and published as an SAE Society of Automobile Engineers paper - free of fuel industry bias.....
Posted by johnchristie