1 INTRODUCTION With the European Union and various nations imposing harsher rules, it is not unexpected that the automobile industry is constantly exploring alternatives to compression ignition (CI) and spark ignition (SI) engines. Homogeneous charge compression ignition (HCCI) engines, which have excellent volumetric efficiency and low nitrogen oxides (NOx) and soot emissions, are a possible substitute. The HCCI engine combines features from both the SI and CI engines.