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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Street vs. Race E85

Tim Wusz: All E85 fuels are not created equal, and as such, the quality can vary dramatically from one E85 blend to the next. Street E85 has just one restriction on the 15 percent non-ethanol portion that is used. That restriction states that the 15 percent non-ethanol content must be either gasoline or gasoline hydrocarbons. This is a very loose stipulation since the quality can vary tremendously from a good-quality gasoline to the cheapest hydrocarbon that the blender has available. In fact, it is actually very uncommon that a high-quality gasoline is used for that 15 percent. It gets even worse in winter months because the Federal Government allows the amount of ethanol in E85 to be adjusted so that flex fuel EFI vehicles will start at ambient temperatures below 20 degrees. During the winter, the ethanol level in E85 can legally be as low as 70 percent with the gasoline component being 30 percent. What this means is that during cold weather when the gasoline component is raised from 15-30 percent of the blend, the potential problem of poor quality doubles with the gasoline portion of the blend.

At Rockett Brand, we have found some E85 that contains less than 65 percent ethanol. This may be OK for flex fuel vehicles, but if a racer is trying to use what he thinks is E85 but the actual ethanol content is lower, his carburetor calibration can be overly rich. Samples taken with 90 percent ethanol have also been reported, which would make the carburetor calibration lean. The point here is that any deviation in ethanol content from the 85 percent standard for a carbureted race vehicle begins to introduce more variables for the racer. In contrast, Rockett Brand E85 is always blended to 85 percent ethanol with hand-selected blending components that comprise the other 15 percent of the blend. The components used have very good octane quality also. The benefit of this consistency is that the racer does not need to be concerned with recalibration of his carburetor every time he gets a fresh batch of Rockett Brand E85. Every batch is the same. Even though the racer must pay attention to weather and track variables, the fuel itself is not a variable. The bottom line is that Rockett Brand E85 is extremely consistent from batch to batch, and the 15 percent gasoline portion of the product contains high-octane gasoline blending stock.

E85 Carbs

Marvin Benoit: When running E85 in a street car, there are several modifications that need to be made to the carburetor. To make the transition from gasoline to E85 easier, Quick Fuel Technology offers carbs ranging from 650 to 1,250 cfm designed specifically for E85. Since E85 requires an air/fuel mixture that’s 30 percent richer than gasoline, we enlarge all the internal passages in our E85 carbs. By opening up the boosters and enlarging the metering block and main wells, we can achieve the necessary increase in fuel capacity. These changes allow you to run the same jet sizes as you would on gasoline, but at the correct air/fuel ratio for E85. Since E85 is more corrosive than gasoline, we use anodized aluminum parts in our E85 carbs as well. If you don’t modify a carburetor when switching over to E85, you can easily run out of jet size. On a carb designed for lower horsepower bracket racing motor, we offer a metering block kit with a modified needle-and-seat assembly and a special diaphragm that resists corrosion. These modifications will allow you to convert a regular gasoline carb over for E85 use. CHP


Quick Fuel Technology
Bowling Green, KY 42101
Rockett Brand Racing Fuel
Mount Prospect, IL


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