Studies concerning the combustion analysis in spark ignition engines generally feature measurements of in-cylinder pressure traces and exhaust emissions. Combined thermodynamic and optical investigations can provide significant insight into specific phenomena and a more complete understanding of combustion processes. While the latter category of investigative techniques gives information on local flame and fluid characteristics, measurements of in-cylinder pressure ensure quick and cost competitive analysis of complex processes that take place inside the combustion chamber. By using both methods, valuable correlations between different phenomena can be obtained, thus providing a complete view based on experimental trials. This work aims to evaluate the capacity of different data analysis procedures to deliver accurate and pertinent results on combustion development, as well as the correspondence between the two types of measurements. Three thermodynamic models for in-cylinder pressure analysis and three imaging techniques were compared within each category of investigative methods; results were also evaluated in a combined way in order to assess each procedure. The more complex thermodynamic model that included a heat transfer correlation was found to offer improved accuracy in the initial combustion phase, as compared to other two simpler methods. (C) 2014 Elsevier Ltd. All rights reserved.