A combustion process with high air/fuel-ratio enables low combustion temperatures and therefore low wall heat losses and nitric oxide raw emissions. On the other hand, the cycle-to-cycle variations increase, particularly for conventional ignition systems. Numerical methods can support the development process to define operating points with highest efficiencies and emissions that meet the regulation limits. However, these models must be able to describe the thermodynamics of the combustion process and the kinetically controlled knocking combustion and pollutant formation for different fuels.