Essentially combination of spark ignition and compression ignition engines, the HCCI engine exhibits low NOx and Particulate Matter (PM) emissions as well as high efficiency under part load. This paper is concerned with the Homogeneous Charge Compression Ignition (HCCI) engine as a new concept in engines and a power source for future automotive applications. In this research, a 4 cylinder diesel engine was converted into a HCCI engine, and propane was used as the fuel. The purpose of this research is to show the effects of fuel flow rate and the temperature of the intake manifold on the performance and exhaust of an HCCI engine.