— In this paper, we propose a control strategy to improve the combustion efficiency of Spark Ignited engines. More precisely, we adapt the spark ignition time according to variations of thermodynamic conditions of the combustion chamber during transients. Sensitivity of a simple proposed combustion model (ordinary differential equations governing the flame propagation phenomenon) is used to compute an open-loop control law. An end-point matching condition is formulated to guarantee that the middle of combustion occurs at an optimal time. Simulation results stress the relevance of the approach.