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CornThere has been a lot of talk over the past few years in the performance automotive circles about this curious new fuel that is slowly cropping up around the country. You may have seen it yourself - the bright yellow pump handles, large E85 banners promoting it's "green" and "renewable" properties, and also it's attractive low price compared to standard gasoline.

What exactly is E85 though, and what are its benefits? Please note this is not an article debating the ethics or questioning the renewable properties of E85. This is an article that quickly summarizes the attributes of E85 over conventional gasoline in high-performance applications

Blended, not 100%

E85 is an approximate mixture of 85% ethanol alcohol and 15% gasoline. There are small amounts of other additives, such as methanol alcohol (to make it unsuitable for drinking), detergents, and emulsion agents (to control moisture and mixture separation).  The specific blend of ethanol to gasoline also varies according to the season - in colder weather E85 is blended with slightly more gasoline to improve volatility and help cold starts and cold idle stability.

flexfuel-badge An E85 Flex Fuel badge.

Flex Fuel

Cars designed to run on E85 fuel are typically labeled as "Flex Fuel" vehicles. This important designation indicates that the car has an "ethanol content analyzer" - a sensor that is able to sense the amount of ethanol in the fuel in real-time. This is important because there is no requirement on the exact blend of ethanol in the fuel that is sold at the pump - between station to station across fill-ups the actual percentage of ethanol to gasoline can vary. In addition to the ethanol content analyzer, the car's computer is also designed to read the sensor and adjust the parameters so the engine can run on the fuel correctly. This involves real-time changes to the fueling and ignition systems to ensure the engine is running correctly on the variable ethanol content.

E85 fuel also has approximately 30% less energy per unit volume than gasoline. This means in order to produce the same amount of power on E85 vs 93 octane gasoline, there needs to be about 30% more fuel. Flex fuel capable vehicles will compensate for the increased ethanol content and will automatically make the necessary fueling adjustments to ensure the car runs correctly.

E85 also produces a much lower EGT/CHT (Exhaust Gas Temperature / Cylinder Head Temperature) than 93 octane gasoline does. This increases the tuning threshold available for E85 fuel and can help prolong the life of exhaust valves and turbocharger turbine components.

E85 Resists Detonation

The biggest advantage of E85 fuel in high-performance applications though is it's much higher effective octane. Octane is measure of how resistant a fuel is to detonation, which is an explosive uncontrolled fuel burn that can cause major catastrophic damage to engines. While 93 octane fuel provides moderately good resistance to detonation, tuning of the engine (particularly in forced-induction applications such as turbocharged or supercharged) is limited by detonation and knock thresholds. Timing can only be advanced so much until the tuner meets the knock threshold of the engine on 93 octane fuel. When tuning a forced-induction car running on E85, the fuel resists detonation so well that the timing can be advanced to mean-best-torque (the point at which timing produces the most torque) and beyond without encountering knock. This massively increased threshold in tuning a car to run on E85 fuel provides the engine with much higher potential for power.

Tuning solutions

Re-tuning an engine computer to take advantage of E85 ethanol fuel by modifying the timing tables.

Well, if E85 can help an engine produce much more power, then why can't we convert all of our cars to use it? Why not fill up your S60R with E85 fuel, get it tuned, and enjoy the fruits of a low-cost high-octane fuel? The main reason is the variable blend of E85 - even though all the pumps are labeled as "E85", the exact percentage of ethanol to gasoline will vary between different pumps, and even on the same pump on different batches of fuel. When tuning a car not designed to run on E85, the tuner needs to compensate and allow for small differences in ethanol content, often times by making the final tune not as aggressive. Sure, the tuner would be leaving 5-7% of power on the table, but the extra margin of safety allows the car to fill up at any E85 capable station without worrying about the exact ethanol content. Some cars not initially designed to run E85 fuel now have aftermarket solutions to enable them to have flex-fuel capability to automatically detect and adjust for variable ethanol content. ECUTek is a notable innovator in this field - their aftermarket ECU reprogramming allows for flex-fuel capability with the addition of an ethanol content analyzer. However, their market mainly consists of Japanese import vehicles such as the Subaru WRX STi or Mitsubishi Lancer Evolution. For the European import market, the main solution is to use a stand-alone ECU - which is a full replacement engine computer such as an offering from MoTeC, ProEFI, or AEM Infinity. Another solution is to purchase pre-blended E85 fuel designed for motorsport use - which has a guaranteed mixture of ethanol and gasoline that never changes. However, purchasing motorsports fuel will negate the cost benefits of using E85 fuel that is available at your local gas station.

E85 requires more flow volume

Injector Dynamics ID1300 fuel injectors are designed to withstand continuous use with ethanol fuels.

What about fueling requirements? Earlier I mentioned that E85 fuel needs 30% more fuel volume just to produce the same amount of power. However, to fully utilize the benefits of E85 fuel and extract the most power possible from the engine, fuel flow will need to be dramatically increased, often times up to double the fuel flow of an equivalent system on 93 octane fuel. Fuel pumps, regulators, and injectors need to be modified to be able to handle the additional flow. Sometimes lines and fittings need to be modified to handle the increased corrosiveness of using a high-ethanol content fuel. Additionally, the lower energy content combined with higher fuel volume requirements for high-power applications also contributes to poor fuel economy - however for many motorsports applications this is a negligible side effect.

Have you ever experimented with E85 ethanol fuels in high-performance applications?

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About the Author: Andrew Peng

4bc258bba12eb53f892c34317c49b78eAndrew is an aerospace engineer and car fanatic that enjoys working on his garage of Volvos and Subarus. When he's not busy attending car meets and shows or taking things apart, he enjoys driving his cars and finding interesting new ways to break them. He can be reached via his personal website at http://andrewpeng.netFacebook, Google+Instagram, or Twitter.


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Written by :
Andrew Peng

Andrew is an aerospace engineer and car fanatic that enjoys working on his garage of Volvos and Subarus. When he’s not busy attending car meets and shows or taking things apart, he enjoys driving his cars and finding interesting new ways to break them. He can be reached via his personal website at http://andrewpeng.net, Facebook, Google+, Instagram, or Twitter.


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