[82mm 4g63]

Originally Posted by 82mm 4g63

I think you're discounting the gains of higher compression ratios, direct injection, turbocharging, and technologies like Saab's LeanBurn. Current flexfuel engines pay approximately 30% efficiency penalty because they are optimized to use gasoline.

A higher octane rating means that a fuel is less prone to unwanted detonation. A higher latent heat of vaporization means that ethanol can help control gas conditions in the combustion chamber by lowering temperatures. By modifying the pressure and temperature, fuel injected into the engine will burn more efficiently and reduce the formation of N2O gases.

Regular flexfuel engines are unable to exploit these properties because theyre optimized for gasoline and run at lower cylinder pressure.

There's a company called Ricardo in Detroit that built a 3.2l twin turbo V-6 that runs on E100. They're claiming fuel economy comparable to diesel engines.

Originally Posted by serialk11r

Dude maybe you should actually read, I said higher compression. Direct injection, turbo, leanburn are not ethanol specific. They also don't pay an efficiency penalty compared to gasoline, if you try burning it just like gasoline the efficiency comes out about the same (maybe a little better due to charge cooling, although that depends on the fuel delivery).

Yeah, I guess I missed the part where you said they weren't ethanol specific I also missed the part where I said they were ethanol specific. I'm sorry.

Current flexfuel engines absolutely pay an efficiency penalty because they are optimized to use gasoline.

An important step toward increasing alcohol fuel demand, then, may lie in providing economical engine technology options that utilize such fuels more efficiently, to compensate for the lower fuel energy density. The FFVs produced today, however, use fairly typical gasoline engines, which, because they must retain dual-fuel capability, are not able to take full advantage of the favorable combustion characteristics of alcohols. Engines optimized for alcohol fuel use, on the other hand, may yield efficiencies that exceed that of state-of-the-art diesel engines—or, about one third higher than that of FFV engines. In earlier engine research at EPA with neat methanol and ethanol, for example, over 40% brake thermal efficiency was achieved over a relatively broad range of loads and speeds, with peak levels reaching over 42%. Similar work has also been performed with E85, yielding up to 20% fuel economy improvement over baseline gasoline engines.
-http://www.epa.gov/otaq/presentations/epa-fev-isaf-no55.pdf


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The [EBDI] engine runs best on a blend with gasoline that is 30% to 50% ethanol, but, Ricardo says, can run on anything from all gas to all ethanol. Ricardo is bringing a GMC Sierra 3500HD pickup to the Washington, D.C., auto show this week that will be outfitted with its V-6 ethanol engine. On gas, it says, the GMC truck gets about 12.7 miles per gallon. On all ethanol, it would get about 12.1 mpg, the company says. But with an optimum blend, it says the engine could get 15 mpg.

Until now, automakers haven't made engines designed especially to run primarily on ethanol. The engines in so-called flex-fuel cars and trucks — able to run on a blend with gas that is 85% ethanol — are actually standard gasoline engines with some fuel system components altered to deal with ethanol's higher corrosiveness.

"We think this could replace conventional engines, and could even replace diesels," says Kent Niederhofer, president of Ricardo.

The key problem with ethanol fuel efficiency is that it contains less energy per gallon than diesel or gasoline — meaning vehicles consume it faster than other fuels. Drivers get fewer miles per gallon using ethanol blends.

But Ricardo says this engine, which it dubbed the Ethanol Boost Direct Injection engine, or EBDI, is tuned to make the most out of ethanol's properties where it has an edge on other fuels. Ethanol has a higher octane rating than diesel or gas, so it's more likely to ignite at just the right point in the engine's combustion cycle. Diesel and gasoline can sometimes ignite earlier or later than intended, causing knocking noises in the engine. Automakers compensate with knock detection systems, but those can cut an engine's efficiency.

-http://www.usatoday.com/money/autos/2010-01-26-ethanol26_ST_N.htm