Although it's not widely available at the pump yet, in time E85 (85 percent ethanol-based
Although there doesn't appear to be a consensus about ethanol with respect to its overall impact on the environment, from a performance enthusiast's perspective there do appear to be real advantages to converting to E85, according to Mike Warfield from GST Motorsports. "From our testing with the readily available E85 fuel we now use in our time attack Impreza L, which is about 105 octane, we've found it's not quite as high a knock resistance as the 116 leaded race fuel we used to use. This might lead you to think that the car would have to be somewhat neutered with regards to power output, but what the ethanol really shines at doing is lowering the cooling charge temp," Mike continues, "allowing us to push the tune a lot harder. As a result, our power output numbers are as good if not better than what we were making with the leaded race gas, and interestingly, we found that with ethanol we are able to go beyond MBT [Minimum Best Timing, the lowest value of ignition advance that produces maximum power] without the motor knocking. Obviously, this is not something you would want to do, but on 116 race gas we would actually run out of effective knock prevention prior to reaching MBT, so being able to go beyond MBT with ethanol really illustrates its charge cooling properties."
GST's corn-powered Impreza L is one of the fastest time attack machines in the country. Or
When I asked Mike what sort of cars he felt would benefit the most from converting to E85, here's what he had to say: "I think the biggest gains to be had would be seen on forced induction cars, where the effective octane rating and cooling charge properties of ethanol can really shine. With a normally aspirated car, there will be some gains when tuned for E85, but not as significant as the gains with forced induction applications [because there's so much more heat generated by a turbo setup]. For modified street cars, whether or not it makes sense to convert to E85 is going to depend on intended use. If the car is being used to commute 50 to 60 miles per day and driven hard on weekends, you have to decide if the power increase is going to be worth it, given that your engine will consume about 30 percent more E85 getting from point A to point B. The other issue is simple availability. Locally we have two stations that carry E85 and they are about 45 miles apart and the next closest station is over 110 miles away, so until more stations start to carry E85 the availability issue will be a major factor when deciding to convert to it or not." It's also important to keep in mind that switching to E85 on an engine designed for standard pump gas will likely result in premature wear on its seals and piston rings, so converting a daily driver is probably not a good idea.
But for weekend warriors who want a better performing fuel in their tank, especially for high-horsepower boost junkies who can really benefit from the cooler combustion temps associated with ethanol, converting to E85 makes a lot of sense. According to Mike, "With our race car we have seen our fuel costs go down substantially, with our weekend fuel bill now roughly a third of what we used to spend when running 116, which is huge for us given we're a self-funded team."