The Undeniable Pros and Cons of E85: Our New High Class Gas
E85, it’s all the rage right now. E85 stands for 85% ethanol and 15% gasoline or other hydrocarbon fuel. Basically, it’s made by distilling good ‘ol corn sugar into alcohol (moonshine) and then blending it with what we consider traditional gasoline to create the desired ratio. According to government regulations, that needs to be somewhere between 53% and 83% which is what you’ll find at your local pump if your lucky enough to be graced with the yellow handle. But what’s the big deal? Corn in a gas tank doesn’t sound all that awesome and if I have to go out of my way to find the dang stuff, it better be good.
Oh we can assure you, it’s good. It’s real good. The properties in E85 offer many benefits that the Subaru STI and Subaru WRX engine absolutely loves. We’ll start with the end outcome and work our way forward. Simply stated, E85 equates to more horsepower & torque with a high degree of reliability. E85 is a more knock resistant fuel than your typical 91 and 93 octane due to its slower burn. It is more resistant to combustion, which allows for a controlled explosion within the cylinders helping avoid the undesired and often terminal detonation. A slow and consistent burn is a highly desirable trait in a fuel as it helps ensure your engine is safe when operating at the limit.
The thermal properties of E85 allow the fuel to burn at a much cooler temperature than your traditional gasoline which leads to significantly reduced engine heat. High exhaust gas temperatures are a cause for concern during any prolonged track event and can significantly reduce the life of your engine if not suited to handle the high heat. E85 burns at a much cooler temperature, which helps protect your engine while also reducing the intake charge temps due to the alcohols unique characteristics. Because E85 features a slower and cooler burn with less risk of knock, you are able to run advanced ignition timing allowing for more boost and power with increased reliability. The net effect of E85 is nearly the equivalent to running a gas in the 105 octane range depending on the ethanol volume.
While this all sounds quite rosy, there are a few things to be aware of when switching your Subaru STI or Subaru WRX over to E85. This high class gas does require you to upgrade your fuel system in order to properly convert to E85 (more on that later). E85 is also hygroscopic, meaning it will attract water from its surroundings. This is less than desirable in a fuel system as water can often cause all sorts of issues once introduced into the engine. Vehicles without upgraded injectors can eventually experience ‘gunk’ or rust rendering them inefficient. E85 also varies widely in total ethanol content from season to season as well as state-to-state. Too low of ethanol content can cause issues in how your vehicle operates assuming it is tuned for an 85% ratio. The good news is, all of these E85 issues are relatively easy to overcome with modern systems developed by brands such as COBB.
So what is needed to successfully and safely convert your Subaru STI or Subaru WRX to E85? For starters, any fuel component that is directly responsible for the efficiency of flow will need to be swapped out. Most importantly, injectors and fuel pump. E85 contains less energy per volume than gasoline. Because of this, more fuel will need to flow in order to achieve the potential power gains. Deatschwerks supplies some of the best fuel pumps on the market with varying levels of efficiency all suited perfectly for the Subaru STI or Subaru WRX. We recommend the DW300c or AEM unit if you’re looking for a pump capable of flowing enough fuel for moderate power gains and developed with the use of E85 in mind. Installation is relatively straightforward with vehicle specific install kits available. The DW300c is resilient to the unique properties of E85 and will continue to operate as new for plenty of years of ownership.
Upgrading your Subaru STI or Subaru WRX injectors is another key piece to the puzzle. In order to flow more fuel, your injectors will need to be able to operate within a healthy duty cycle and move enough E85 to feed the requirements of the engine. As mentioned earlier, E85 is hygroscopic. Upgrading your injectors to a stainless steel variant will also help ensure the smooth operation of all the tiny moving pieces within the injector. The stainless steel internals will help avoid rust and the build up of gunk if left inoperable for any length of time. It is also highly recommended that at a minimum you start your Subaru STI or Subaru WRX once or twice a week to keep the E85 from staying stagnant.
While a fuel pump and injectors will get you going down the right path, it is also wise to outfit your Subaru STI or Subaru WRX with some of other nice to have amenities such as a COBB flex fuel sensor kit and Cobb fuel pressure regulator. The E85 flex fuel sensor will allow you to monitor the ethanol content within each new batch of gas that you pump. Because E85 ratios can vary widely from station to station and your tune is based on 85% ethanol, it is important to know the composition of your gas as well as allow your ECU to adjust accordingly. The upgraded E85 fuel pressure regulator will insure the smooth operation of your fuel system with a consistent fuel pressure level at all times.
While E85 may not be for everybody, it certainly has undeniable potential for high horsepower Subaru STI or Subaru WRX applications. If being compared to a traditional octane rating, E85 is essentially somewhere in the ballpark of running 105 pumped locally at your nearest gas station (where available). An ancillary benefit to converting is the price per gallon of E85. At the time of this article, E85 is selling for an average $2.77 per gallon where as 91 octane is priced at $3.95. If you’re prepared for the transition, it is essentially a no brainer if you are lucky enough to be graced with one of the yellow pumps in your town.