AbsractA detonation model for spark ignition engines has been developed. Basis for the work is the Phenomenological Spark Ignition Engine Simulation model (PSIES) recently developed at the University of Calabria coupled to an algorithm for determination of the cold flame induction time, as proposed by Douaud and Eyzat for primary reference fuels. The effect of fuel composition on the thermodynamic properties of the unburned mixture has also been taken into account.Model predictions have been compared to experimental results for a CFR engine, obtaining very good agreement. Finally an Octane requirement map for a production engine of which some pressure data in absence of detonation were available, has been computed. More work will however be needed in particular for optimizing the values of the various parameters.