Concerns for fuel economy and reduced emissions have turned the attention of automotive internal combustion engine manufacturers to the exhaust system and towards technological system development to account for the significant levels of potential energy that can be recovered. The present volume on “Automotive Exhaust Emissions and Energy Recovery” for both gasoline and diesel engines is therefore both timely and appropriate. Whereas diesel engines have been predominantly turbocharged, only a relatively small percentage of gasoline engines are similarly equipped, which has led to significant efforts by engine manufacturers in recent years to downsize and down-speed these engines. On the other hand, the relative focus in diesel engine development in terms of emissions and exhaust energy recovery has shifted toward devices other than the turbocharger for enhanced energy recovery and emissions control technologies in order to allow the diesel engines of the future to keep up with the dual-demand for very low emissions and increasing levels of fuel economy. The book focuses on the exhaust system and the technologies and methods used to reduce emissions and increase fuel economy by capitalising on the exhaust gas energy availability (either in the form of gas kinetic energy or as waste heat extracted from the exhaust gas). It is projected that in the short to medium term, advances in exhaust emissions and energy recovery technologies will lead the way in internal combustion engine development and pave the way towards increasing levels of engine hybridisation until fully electric vehicle technology can claim a level of maturity and corresponding market shares to turn the bulk of this focus away from the internal combustion engine. This book is aimed at engine research professionals in the industry and academia, but also towards students of powertrain engineering. The collection of articles in this book reviews the fundamentals of relevance, recent exhaust system technologies, details recent or on-going projects and uncovers future research directions and potentials.