A simple thermal model for flame propagation is adapted to engine conditions and used to trace back engine parameters via computer simulations to basic physical properties. The competitive constraints imposed by piston motion on ignition and flame propagation are revealed and the principal possibilities investigated to relieve these constraints. General criteria for enhanced ignition and flame propagation are given. The theoretical results are compared to extensive measured engine data showing an excellent agreement between model predictions and easily measureable engine dependencies. By relating basic data to implicitly given engine properties the optimization of engine performance is substantially facilitated.