Biodiesel is widely used as a diesel component worldwide as well as in Thailand. Even there are so many research papers studied about biodiesel combustion, performance and emission, the various sources of biodiesel and engine technologies makes it more complicated to conclude how biodiesel combustion react to the engine behavior, especially for transient state operation. Some of biodiesel user feels that the presence of biodiesel component in diesel fuel influence on poor engine driveability even only 5% V/V. While, there is a few publications comment on the low sensitivity of diesel fuel ignition delay quality when running with advance diesel common-rail DI engine.The first experiment was done on low pressure diesel combustion which represented the conventional diesel technology, aiming to study the effect of fuel injection pressure on biodiesel combustion. The results shown that, the higher content of biodiesel blended fuel has no significant effect on diesel combustion.The second experiment focused on the factor that affect to diesel engine combustion base on steady-state running with the common-rail DI technology. Due to the availability of pilot injection, the result of using biodiesel blended fuel was different from condition to condition.The third experiment intended to investigate the differentiation of engine combustion when comparing the pure biodiesel with base diesel especially in transient operation. This test was focusing on the engine response or driveability when fuelling with biodiesel blended fuel.