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Energy independence and reduction in pollutant emissions are a center of interest for several researchers and car manufacturers. Renewable fuels have gained in popularity because of their sustainability and, in some cases, lower amounts of greenhouse gases. Moreover, energy diversification is also required by all countries. One possible solution is the use of biofuels such as ethanol, methanol, etc. These biofuels have been shown as good candidates as alternative fuels for vehicles because they are liquid and they have several physical and combustion properties similar to gasoline. Alcohols have also a higher octane number and oxygen content than gasoline. This allows the alcohol engines to have much higher compression ratios (CRs), and thus, better BTE (brake thermal efficiency). Brazilian car manufacturing industry has developed flexible-fuel vehicles, introduced in 2003, which became a commercial success.

Nowadays, many researches are being carried out to replace the diesel by alternative fuels. Biodiesel and ethanol are strong candidates for this purpose. However, the experimental study of the combustion of biofuels in engines is not an easy task. Due to the large differences between the properties of the new fuels and the conventional diesel, radical changes may be needed in current engines, developed specifically for the fossil fuel. So, the experimental study of ethanol compression ignition (CI) combustion is not simple to be obtained in conventional engines. Therefore, some experimental apparatus, such as a rapid compression machine (RCM), are useful to conduct this kind of study. This paper describes the RCM adaptations made in order to run CI combustion tests using Ethanol-Powered (ED95) and Diesel (S50) for different compression ratios and injection timing.

Gasoline is a volatile, inflammable mixture composed of olefinic, paraffinic, naphthenic and aromatic C4-12 hydrocarbons. Gasoline presents low contents of oxygenates and traces of sulfur, nitrogen and metals which introduce instability. In several countries, like Brazil, ethanol is used as an alternative fuel and as an octane improver. Nevertheless, hydrocarbons present in the fuel slowly react at room temperatures with atmospheric oxygen and with each other. This promotes changes in their physical-chemical characteristics. The process is observed throughout all the fuel production and use chain, increasing fuel density. These resinous, polymeric, insoluble and nonvolatile materials that are formed with high molar mass, commonly called gums, form deposits along the vehicle fuel system. Their accumulation can cause engine wear and have adverse effects on engine efficiency, performance and durability.