Homogeneous charge compression ignition (HCCI) combustion is a hybrid concept of compression and spark ignition combustions. It is a promised solution to environmental and fuel economy concerns for internal combustion engines. In this mode of combustion, a lean premixed charge combusts simultaneously from multiple sites. Utilizing very lean mixtures, and the lack of any obvious flame propagation, considerably reduces in-cylinder NOx formation. In order to make the HCCI engine a feasible alternative to the SI and CI engines, several items must be elucidated. Control of the combustion timing is one of the most important of these items to be resolved. Combustion timing should be controlled in order that heat is released at the best time in the engine cycle. In this study, a Waukesha CFR single cylinder research engine with variable EGR was used to be operated in HCCI combustion mode fueled by natural gas and n-heptane. The main goal of the experiments was to make an attempt to control the combustion timing and duration by studying different approaches such as varying EGR rates, intake charge temperature and compression ratio. The main objective of the study is the investigation of how EGR rates and intake charge temperature can affect the HCCI combustion. In order to achieve this goal, a modified first law apparent heat release model, developed by the authors, was utilized. Utilizing this model, guarantee obtaining a well-behaved and accurate apparent heat release trend and magnitude in HCCI combustion engines. Also, the influence of EGR and intake charge temperature on emissions was discussed. Results indicate that applying EGR has profound effect on combustion phasing, leading to a retarded SOC and prolonged burn duration. It is favorable regarding fuel economy, too. The influence on emission characteristics is desirable with respect to NOx formation and unfavorable in the case of CO and HC emissions in a dual fueled HCCI combustion engine. Intake charge temperature has profound effects on in-cylinder charge pressure and temperature. It alters heat release rate magnitude and phasing. This parameter also affects indicated power and fuel consumption. Measured emissions have also shown changes due to variations of this initial condition.