Daily Slideshow: Everything to Know About Running E85

What Exactly Is This E85 Stuff?

Most fuel sold at gas stations today is not straight gasoline, but instead a fuel blend containing a percentage (typically 10-15%) of ethanol. Ethanol is a renewable, "corn-based" fuel that is achieved by fermenting plant sugars, thus producing an alcohol fuel. When mixed with gasoline, it tends to actually reduce fuel efficiency and often results in minor power losses for an engine that was designed to run premium unleaded fuel. E85, on the other hand, is a blend containing 85% ethanol and only 15% gasoline that makes for an octane rating of somewhere between 100-105. With such high octane ratings, more compression and a higher knock resistance can be achieved, therefore more horsepower.

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The Benefits Are Real!

When matched up against gasoline, there are some glaringly obvious benefits to using E85 as your choice of fuel in a performance application. With E85 having such high octane ratings that are anywhere from 8-12 octane numbers higher than 93 unleaded, it allows forced-induction engines to run additional boost levels and naturally aspirated engines to run much higher compression ratios. Ethanol also provides improved cooling properties over gasoline by absorbing much of the heat from the intake charge allowing for a much cooler and denser air-fuel mixture to enter the cylinders. When combining the octane rating with its cooling properties, the resistance to detonation is actually much higher than the octane rating alone would suggest. Additionally, E85 tends to burn a bit cleaner than gasoline and reportedly leaves fewer carbon deposits on components such as pistons, valves, etc. In short, E85 provides race-fuel power capabilities at a price approximately the same as a regular gallon of pump gas.

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Okay, Gimme The Bad News...

At this point, using E85 as your choice of fuel may seem like a no-brainer, but there are some drawbacks that folks should consider before making the switch to corn. Perhaps the biggest issue individuals have with running E85 is that it contains roughly 2/3 the energy of gasoline because its air-fuel ratio for proper combustion is around 9.8:1 compared to gasoline's 14.7:1 ratio. What this means is approximately 35% more E85 is being injected into the engine which hurts fuel economy. To make matters worse, E85 fuel stations can be few and far between since only about 4-5% of the stations in the US carry E85. Another major hurdle with E85 is that it is quite hygroscopic (naturally absorbs moisture from the atmosphere) and can cause corrosion to set in rather quickly in the fuel system if the car is not regularly driven. Lastly, the actual ethanol content in E85 can widely vary in different areas from anywhere between 51-85%. The consequences of running E85 that has a significantly lower ethanol content in a car tuned for 85% ethanol content can have catastrophic results, aka things can go boom!

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A Flex Option You Say?

Fortunately, fuel-injected applications are capable of using a "Flex-Fuel" option that can adjust tuning on the fly to compensate for the fuel being used. Certain vehicles may come from the factory already fitted with a Flex-Fuel setup, but many aftermarket ECU's also support the Flex-Fuel option. In short, a Flex-Fuel setup utilizes an ethanol content sensor that is placed somewhere in the fuel system to measure the exact percentage of ethanol/gasoline and sends this info back to the ECU. The ECU can then dynamically adjust the timing, fueling, enrichment, boost, etc. to ensure the engine is happy. What is nice about a Flex-Fuel setup is that it can accommodate 91 octane fuel all the way up to true E85 and every mixture in between. This allows your car to be driven anywhere without the worry of running out of fuel before making it to the next E85 station because you can stop off for regular old gasoline when going on a lengthy trip.

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How To Make The Switch

In a carbureted application, the switch to E85 is fairly straightforward as it simply requires a carburetor conversion kit (jets, metering block, needles & seats, accelerator pump nozzles) or an entirely new carb designed for the E85 as well as a capable fuel pump, compatible fuel lines, and an E85 regulator & fuel filter. Most modern fuel-injected vehicles already have alcohol-resistant fuel lines and seals made of Viton that will not degrade with E85, so it is often just a matter of upgrading a few fuel system components. The installation of a high-output fuel pump and a larger set of injectors will often do the trick, but the real magic is in the ECU tuning to allow the engine to make the most out of its new elixir. Additionally, kits are available with all the items needed to make the switch including a simple wiring harness, ethanol content sensor, fuel filter, and ECU tuning to get you up an running in no time. While E85 is best suited for engines in a high state of tune that are running elevated compression ratios or loads of boost pressure, it can still provide a 5-7% increase in power on a relatively stock naturally-aspirated engine. What is not to like about making the switch to corn fuel?

>>Join the conversation about Running E85 right here in LS1Tech Forum.

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