The modeling of turbulent combustion is a crucial problem for the numerical simulation of flames and combustion chambers. In this paper turbulent combustion is discussed with a lagrangian model which is useful to study turbulent combustion problems. A coupling between this lagrangian model and a presumed pdf method is used with complex chemistry. The validation of the kinetic mechanism was studied before integrating it in the computer code for reciprocating engines. The results of computations with the present model are compared with the experimental results obtained from experiences obtained in our laboratory and from PSA engine. These comparisons between modeling and experiments show a good agreement.