Ethanol In Use
Pure ethanol fuel is available in Brazil where many cars have been designed to use it. 100% ethanol is unlikely to ever be used in North America or Europe. This is because ethanol is hard, if not impossible, to ignite at temperatures below 10oC. Our ethanol fuel always contains at least 15% gasoline to ensure reliable ignition in a cold engine. Once the gasoline ignites, it “pilots” ignition of the alcohol.
Ethanol is a very high octane fuel with an octane rating around 125. An engine designed to run on E-85 (85% ethanol) could have a compression ratio of 12:1 or higher. Power output could then be (perhaps) 30% higher than the same engine with an 8:1 compression ratio.
In fact, ethanol and methanol are still favoured fuels for drag racers which combine a high compression ratio with supercharging to produce awesome power. The very high octane value of alcohols makes this possible.
However, an engine with a high compression ratio is limitited to using only pure ethanol or E-85. It would self-destruct if you ran it on straight gasoline with a far lower compression ratio.
Another issue is fuel consumption. The ethanol molecule contains about 2/3 of the energy of gasoline. That means a car which might manage 600km on a full tank of gasoline would only go 400km on a tank of E-85. To make up for this, if a litre of gasoline sold for $1.00 (we wish!), a litre of E-85 must sell for $0.65-$0.70 to give equal value. Although the ethanol is subsidised, it’s price is not brought that low. At today’s fuel prices, many motorists are avoiding ethanol-enriched fuel simply because they feel they cannot afford it!