The auto-ignition predictions of the Shell hydrocarbon fuel ignition model have been improved for initial conditions similar to those in diesel engine environments. A series of modifications were made to the model, including a more accurate calculation of the heat release of the fuel, a new mass balance for the products of the termination reactions, and the enthalpies of the Shell model species, R*, B and Q were revised. In addition the twenty-six kinetic parameters of the revised model were determined using a genetic algorithm optimization methodology guided by auto-ignition results obtained from a detailed chemical kinetic mechanism. The optimization was performed for a broad range of conditions that is representative of the operating conditions in diesel engines at the start-of-injection (SOI). This range includes: equivalence ratios from 0.5-4.0, initial pressures from 40 -120 bar, initial temperatures from 650 K to 1175 K and EGR percentages from 0 -75%. The model constants were optimized for two single component hydrocarbons species, n-heptane and tetradecane, that are representative of diesel fuel. Finally, the model was implemented into the KIVA-3V CFD code and a series of engine simulations was performed in order to assess its agreement with experimental data for engine applications. The results were found to be promising in both cases of short and long ignition delays. (C) 2003 The Combustion Institute. All rights reserved.