Engineering Question #1668

Johnathan, a 19 year old male from Sydney asks on November 2, 2003,

What happens when you use ethanol (unblended) in a standard, unleaded car engine? Will it work?

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The answer

Barry Shell answered on November 2, 2003

It works. 40% of all the cars in Brazil use 100% ethanol as fuel. According to Mr. Henry Joseph Jr., Manager of the Emissions and Tests Laboratory in Volkswagen-Brazil, "Compression ratio is similar but pure ethanol allows more compression ratio. Camshaft is similar in the blend but you can modify it for the pure ethanol engine. Valves are similar for the blend but pure ethanol engine requires new surface material. Seat valves are similar but pure ethanol requires new material. Fuel injectors have similar flow capacity for the blend but in Brazil we have changed to stainless tube for the blend and also the pure ethanol engine fuel injector has higher flow capacity also stainless steel. Spark plug for the blend is similar but the ethanol engine it's colder heat high eighty S. U. for the fuel injection system is necessary new strategy and calibration both blends and pure ethanol. Of course due to the different batteries for the blend are similar to gasoline engine but you require higher capacity for pure ethanol engine. Canister requires pull flow for the blend but not necessary for the pure ethanol engine. Fuel parts require new surface coating, protection and seal connectors for the ethanol gasoline blend and stainless steel for the ethanol engine. Catalyst converter is similar for the blend and closer to the exhaust manifold for the pure ethanol engine. Cold start support is not necessary for ethanol blend engine but necessary for the pure ethanol engine. Comparing the performance, the blend allows 3% more power and 10% more power in the ethanol engine. Is higher in the blend 2% and 6.5% higher in the ethanol engine. Maximum speed is 3.2% higher in the blend and 5.3% higher in the ethanol engine. Acceleration time reduced is almost 5% less in the blend and more than 10% lower in the ethanol engine. Consumption unfortunately is higher 2% higher in the 22% blend and 32.4% higher in the ethanol engine." He goes on to talk about the exhaust emission differences between the two kinds of engines. A blend of ethanol and gasoline appears to be the best option for now.

Mary Giglio, Renewable Fuels, USA answered on November 3, 2003

It is not recommended to use unblended ethanol in a standard vehicle not designed to operate on high blends of ethanol.  There are millions of flexible fuel vehicles built in the U.S. that are capable of operating on up to 85% ethanol (not 100%), and changes are made to some of the fuel system parts, as well as a sensor added so the car can detect what level of ethanol is in the vehicle.  For more information on these vehicles, please visit

In the U.S, all vehicles marketed are warranted to operate on blends containing up to 10% ethanol.

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