In this study, heat and flow in a four cylinder direct injection diesel engine combustion chamber has been simulated by using AVL Fire ESE Diesel. In order to clarify the effect of the combustion chamber geometry on the flow area prop-erties, the bowl geometric shape of two different pistons, one of the combustion chamber as a standard, was taken into account in the flow analysis. Standard combustion chamber and modified combustion chamber geometries have been compared. The simulation results showed that the bowl shapes of the combustion chambers are quite effective on temperature-spray droplet distribution, turbu-lence kinetic energy distributions, turbulence velocity distributions and laminar flame speed distributions at the end of the compression stroke. The fuel reaches the cylinder wall more easily and then, the temperature distribution in the cham-ber is lower as a result of evaporation of the fuel with modified combustion chamber. Average turbulent kinetic energy value in the MCC type combustion chamber is 10.53 m²/s², in the standard combustion chamber type combustion chamber this value is 8.35 m²/s² at 720° CA. Turbulence velocity distribution is spread over a wider area in the modified combustion chamber geometry. As a re-sult of the large area of turbulence, the laminar flame velocity has also increased in this chamber geometry.