Volumetric efficiecy, as seen...
Volumetric efficiecy, as seen from this dramatic in-cylinder view of combustion, can be enhanced through the use of ethanol thanks to its higher heat of vaporization. Courtesy Of E3 Spark Plugs
Why is this important? Before a fuel combusts, it must exist as vapor mixed with air, using oxygen in the atmosphere as the source of its oxidant. Therefore, as liquid fuel is introduced into the manifold either by carburetion or fuel injection, it must first change from the liquid to vapor phase and sufficiently mix with the air before it will combust.
The energy required to vaporize the fuel comes mostly from the air, but a portion actually comes from engine intake surfaces as the fuel vapor contacts it. However, it is most ideal to use as much of the air for vaporization to maximize volumetric efficiency. If a fuel has a higher heat of vaporization, the intake air temperature will be reduced, resulting in better volumetric efficiencies as the inlet charge has a higher density. From this, one would expect significant gains in torque performance with ethanol relative to gasoline, and this will be shown to indeed be the case.
In published research work conducted by General Motors, full-load data of a four-cylinder, naturally aspirated spark-ignition direct-injection flex-fuel engine running on E85 demonstrated a near 15 percent increase in specific output relative to production gasoline counterparts, while showing an improvement in part load operation of 3-6 percent. These gains were associated with reduced heat rejection, increased volumetric efficiency, and increased dilution (EGR) tolerance.
As the Circle Track team publishes more of our testing results in the near future, we believe the readership will be pleasantly surprised with the power and torque results from a modern stock car engine using E85 as the fuel.
Beyond the power benefits that ethanol can provide there are two other big factors that make ethanol an attractive fuel for circle track applications. First, it's renewable; and second, it's clean-burning. In addition, since ethanol is less volatile than gasoline, there's a reduced chance of explosion in spills and accidents. And although ethanol is more corrosive than gasoline to certain materials, it is less toxic to the user.
This Brazilian-made van runs...
This Brazilian-made van runs on ethanol produced from that country's vast sugar cane plantations. Courtesy Of Argonne National Laboratory
The renewable factor is significant. In the United States, studies indicate that we could eventually displace about one-third of our imported oil through renewable fuels. Brazil-an excellent example of a country displacing imported oil with renewable biofuels-uses approximately 25 percent ethanol grown from its vast sugar cane resources in its fuel. Sugarcane, like all photosynthesizing plants, grows by ingesting atmospheric CO2 and, through a complex process, converts it into sugar and organic compounds (an organic compound is simply a molecule that contains carbon and hydrogen).
Engineers specializing in alternative fuels use the word "feedstock" to describe the raw material used to create ethanol. In effect, you can manufacture ethanol from anything green that has carbon and hydrogen as part of its chemical make-up. Consequently, there are several levels of feedstocks, first generation, second generation, and so on.
Brazil's sugarcane and the U.S.'s corn are two examples of first generation feedstocks used to generate ethanol. However, there are many second- and third-generation ethanol feedstocks available such as residuals from crop and forest harvests (corn husks, corn stalks, or sawdust), perennial grass, fast-growing trees, and, one day, even algae.
In other words, the leaves that fall from the trees in your yard can be collected and turned into ethanol. Not only that but advancements in what scientists call biomass catalytic, cellulosic, and even algae-based technologies are demonstrating that these sugar and organic compounds can be converted to ethanol fuel economically.
In addition to being renewable, the aforementioned second- and third-generation feedstocks come from atmospheric CO2 (that's carbon dioxide in the air we breathe); remember, these feedstocks are essentially plant leftovers that have already taken part in photosynthesis when they were living and have converted atmospheric CO2 to the all-important oxygen. A second-generation feedstock's contribution as the base for a renewable fuel significantly reduces the well-to-wheels global-warming gas.
Well-to-wheels is another term that gets bantered around the green racing world quite a bit. As its name implies, it's an analysis of the amount and type of energy (including emissions) used from the time you harvest the fuel from its source (well) to the time it is completely spent in your vehicle (wheels).