This book attempts to provide a simplified framework for the vast and complex map of technical material that exists on compression?ignition engines, and at the same time include sufficient details to convey the complexity of engine simulation. The emphasis here is on the thermodynamics, combustion physics and chemistry, heat transfer, and friction processes relevant to compression?ignition engines with simplifying assumptions. Since details are covered from the fundamentals, it will be a valuable tool for both undergraduate and postgraduate students, as well as for practising engineers.