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TECH Photos & Text by Vahok Hill
UNDERSTANDING ALCOHOL FUELS PART II In issue number five of Dirt Empire Magazine, Vahok Hill introduced the subject of why alcohol is a popular racing fuel. In this concluding section, he looks at some of the particular properties of alcohol fuels and the potential for new ways of producing alcohol fuels in the future. IT IS OFTEN THOUGHT that alcohol makes power because it has a greater amount of energy. This is not completely true; in fact, the types of alcohols that are commonly used in racing have less heat energy than gasoline based on the volume. There are in fact four types of alcohols, but only methanol and ethanol are currently used as fuels in the racing world. The other two types of alcohols, propanol and butanal, are not used commonly used as fuel. Propanol has more uses as an industrial solvent than as a fuel. Butanol, however, has some unique characteristics; it is the one alcohol that most closely mimics gasoline from an energy density perspective. That is one of the reasons that the Stochiometric air fuel ratio is the closest to gasoline.
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Butanol due to its chemical makeup is not as corrosive as methanol or ethanol. While all of this sounds really great, as with most things there are some issues that prevent butanol to be a viable racing fuel at this point in time. First is that it has a fairly high melting point and at cooler room temperatures more closely resembles light grease or jell, than a liquid fuel. However, it does mix well with gasoline and that has some real positives for the passenger car world; however, it is not a real boon to the racing world, yet. For those reasons, we will still focus our attention on methanol and ethanol. From a race car handling perspective, alcohol will cause the racer a bit more problems. Since alcohol contains less heat energy than gasoline, you will be required to run more of it, that means more weight at the start of the race and due to the higher consumption rate the car will become lighter more quickly as the race progresses. Why is this a bad thing? Because it will change your weight and balance to a greater degree than you would have with gasoline, as the fuel burns off, yes gasoline burns off and the car will get lighter as well, it is just that
DIRT EMPIRE MAGAZINE • ISSUE 06 - 2021
with alcohol it will happen at a greater rate, and not only will you have to deal with the ever-changing track conditions you will have to develop a set up that will not go away as the car gets lighter. Or you can develop a setup that favors the car later in the race. The point is that the use of alcohol will not only mandate fuel system changes it will also mandate a different setup than gasoline. This is just one more problem for the chassis guy to chase / solve, as if their job is not difficult enough. So, just why does alcohol make more power than gasoline if it has less energy per pound than gasoline? Good Question. Obviously, you will have to run more of the alcohol-based fuels to get the same power, how much more will depend on the type of alcohol you are running. With methanol and ethanol, it is about 40% more than gasoline. Let me espouse some of the good characteristics that alcohol brings to the table. First, when you burn alcohol, one of the byproducts of combustion is oxygen. This helps propagate the combustion process and is a power adder. Another is the cooling effect of alcohol as it “vaporizes” in the inlet track. This helps create denser air as the fuel/air enters the engine, another positive. The cooling effect also helps to cool the engine, at least on the inlet side of the equation. Remember producing horsepower is all about creating and controlling heat. Another positive feature about alcohol that is seldom discussed but is a very key reason that more power is generated with alcohol, is that the incoming fuel charge, the mixture of air and alcohol, is easier to compress
