E85 Fuel Switch - How It Works

Thinking About Switching to E85? Here’s How it Stacks up to Gasoline, and Some Tips for Making an Easy Transition

Stephen Kim Aug 18, 2011 0 Comment(s)
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Is it E85 or E70?

1110chp 05 O  E85 Fuel Switch Racing Fuel 2/6

Tim Wusz: Consumers who fill up on E85 assume that it’s 85 percent ethanol, but depending on the time of year, that’s not always the case. Since ethanol requires more heat to vaporize than gasoline, modern flex fuel vehicles run into cold start problems when the ambient temperature drops below 20 degrees F. Consequently, during cold weather months the Federal Government allows up to a 30 percent gasoline content in E85, which really makes it E70, to ensure that cold starts are possible. This creates a new set of problems. While flex fuel vehicle with EFI can adapt to the different amounts of gasoline because of the feedback system that controls the air/fuel ratio, carbureted engines don’t have this luxury. As a result, small changes in the amount of ethanol content will cause air/fuel ratio changes that have a significant effect on vehicle driveability. As the amount of ethanol in the fuel is decreased, the mixture becomes richer. If the amount of ethanol was increased, the mixture would become leaner and eventually too lean. In either case, the carburetor would have to be re-jetted to obtain best performance.

Checking Ethanol Content

Marvin Benoit: One of the undesirable qualities of E85 is that it doesn’t light off as easily as gasoline in cold weather. What you think is E85 might actually be E70 in the winter, which requires different carburetor calibrations. To help you measure exactly what concentration of ethanol is in your fuel, Quick Fuel Technology offers an e-checker kit. It’s basically a test tube that you first fill with water, then with E85. Next, you shake it up, and as the ethanol separates from the gasoline, it will float to the top. Depending on which marked line the ethanol comes up to on the tube, it will tell you exactly how much ethanol content is in the fuel in question. From there, you can tune your carb accordingly.

Required Fuel System Mods

Tim Wusz: Since most cars aren’t designed to run on E85, their fuel systems must be modified to make them ethanol compatible. Ethanol is somewhat corrosive, but not as corrosive as methanol. To be on the safe side, we suggest to our E85 customers that they have a methanol compatible fuel system. This means that the fuel pump, fuel lines, injectors or carburetors, fuel tank, and fittings must be compatible with methanol to ensure that they will hold up to ethanol. Usually, anodized aluminum fittings are OK.

Cost Advantage

Tim Wusz: E85 is often cheaper at the pump than gasoline, but in many instances it might actually cost more to run E85 than gasoline. First off, there is a $0.51 per gallon subsidy contributed by the U.S. Federal Government to encourage people to use E85 in flex fuel vehicles, and any cars that have been converted to run on E85. Even when E85 fuel is less expensive than 87-octane gasoline, it is usually not cost effective to use E85 because the system must be calibrated to run approximately 40 percent richer based on the stoichiometric air/fuel ratio. Unless E85 is about two thirds the cost of gasoline, your fuel costs will be higher with E85.


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