Performance of Palm Oil-Based Biodiesel Fuels in a Single Cylinder Direct Injection Engine 15 Performance of Palm Oil-Based Biodiesel Fuels in a Single Cylinder Direct Injection Engine Azhar Abdul Aziz*; Mohd Farid Said* and Mohamad Afiq Awang* * Automotive Development Centre, Faculty of Mechanical Engineering, University of Technology Malaysia, 81310 Universiti Teknologi Malaysia, Skudai, Johor, Malaysia. E-mail: azhar@fkm.utm.my INTRODUCTION Direct injection diesel engines are fuel-efficient power plants for automotive applications because of their superior fuel economy over spark ignition and indirect injection engines. However, the rising cost of diesel, stringent emission regulations and depletion of petroleum reserves are forcing us to search for new sources of energy. In the quest to reduce greenhouse gas emissions, biodiesel is a fuel to consider. Biodiesel refers to methyl or ethyl esters derived from vegetable oils (Reed, 1993). It can also refer to pyrolysis products, diesel-vegetable oil blends, microemulsions of alcohols and water in vegetable oils and fermentation butanol. Vegetable oil was in fact the first diesel when Dr Rudolf Diesel ran his then newly developed engine on it in 1895. He successfully demonstrated his engine at the World Exhibition in Paris in 1900 using peanut oil. Biodiesel is an alternative fuel that may help reduce the world’s dependence on fossil fuels with very significant environmental benefits. It is an oxygenate, sulphur-free and biodegradable fuel. Its content of oxygen helps improve its combustion efficiency. Biodiesel has gained much attention in recent years due to the increasing environmental awareness. It is produced from renewable resources and, more importantly, is a clean burning fuel that does not contribute to the net increase of carbon dioxide. Malaysia has embarked on an extensive palm oil-based alternative fuel programme since 1982 (Choo et al., 1995). The programme includes the development of production technology to convert palm oil to palm methyl esters (palm diesel), a pilot plant study of palm diesel production as well as exhaustive evaluation of using palm diesel in conventional diesel engines (both stationary and in vehicles). A new phase of the programme started in 2002 to investigate blending palm oil with conventional diesel. Various blends incorporating different palm oil products, such as processed liquid palm oil (PLPO) and bleached and deodorized palm oil (RBDPO) with petroleum diesel are being evaluated as possible diesel substitutes for industrial (Ahmad et al., 2001) and vehicle fuels. Blends of palm oil are promising renewable fuels for diesel engines and have been paid more attention in Malaysia. However, palm oil in diesel changes the fuel’s physico- chemical properties, including viscosity, cloud point, cetane number, heat value and boiling point. For example, the viscosity is decreased causing the cetane number to fall. A high cetane number usually ensures good cold starting, reduced noise and long engine endurance. Therefore, the properties of blend must be maintained within certain limits. Any alternative fuel for an internal combustion engine should satisfy certain criteria, such as requiring minimum engine modification, offering uncompromised engine life and being not hazardous to human health and the environment during production, transportation, storage and utilization. The fuel also must be low cost, renewable and in abundant and stable supply. Ethanol is a possible alternative fuel for diesel engines. But, its cetane number is too low, which resulting in excessive ignition delay and knock. In addition, its