Biodiesel, as a renewable fuel that has the potential to replace diesel fossil fuels. With properties in the form of viscosity, density, and surface tension, which are higher than diesel fossil fuel, biodiesel produces poor spray characteristics, and also the high cetane number and oxygen content so that the ignition delay is shorter causes the start of combustion will shift more forward, therefore need to improve injection parameters including injection pressure and timing. The aim of this research is to get the optimal injection parameter optimization so as to improve engine performances and emissions. The method used is to increase the fuel injection pressure from 200 to 230 kg/cm2 and the injection timings were retarded from 22° to 16° BTDC. The results show that increasing injection pressure can improve spray characteristics as indicated by shorter penetration and smaller spray diameter of 30% and 9.8%, respectively and increase in spray spread angle of 21.9%. Then the optimization of engine performances and emissions, obtained at an injection pressure of 230 kg/cm2 and injection timing of 16° BTDC with an increase of power and thermal efficiency of 3.9% and 13.9%, respectively and reduction in smoke emissions of 45.2% at high load.

Biodiesel as an alternative fuel can replace fossil fuels. However, biodiesel has a higher value of viscosity, density and surface tension to fossil fuels. Increasing the injection pressure on the injector is one solution to overcome the problem of high viscosity, density, and surface tension in biodiesel. This study aims to determine the effect of increasing injection pressure and injection timing variations on spray characteristics, performance and exhaust emissions diesel engine. Injection pressure namely 200, 210, 220, 230 kg/cm 2 by setting the rotation of adjusting screw the injector. The results of this study were obtained by increasing the pressure injection of biodiesel fuel by 230 kg/cm 2 resulting in fuel spray characteristics better than the standard 200 kg/cm 2 and resulting improvements in the penetration length, spray angle, the average diameter size of each 30%, 28%, and 9.78%. And performance improvements and exhaust emissions also occur, namely Thermal Efficiency, Specific Fuel Consumption, and Smoke Opacity with values of 16.99%, 14.15%, and 46.39% improved respectively.