A system and method for determining mass fraction burned in an internal combustion engine includes a plurality of engine sensors and a control module determining a ratio of specific heat from a combination of one or more from the group of exhaust gas temperature, injected fuel quantity, air quantity inside a cylinder, mass air flow, air fuel ratio, manifold pressure and a residual gas amount determined from the plurality of engine sensors. The control module includes a mass fraction burned module determining a mass fraction burned in response to a cylinder volume, and the ratio of specific heat. The control module controls an engine parameter based on mass fraction burned.