Internal-combustion engine, any of a group of devices in which the reactants of combustion (oxidizer and fuel) and the products of combustion serve as the working fluids of the engine. Such an engine gains its energy from heat released during the combustion of the nonreacted working fluids, the oxidizer-fuel mixture. This process occurs within the engine and is part of the thermodynamic cycle of the device. Useful work generated by an internal-combustion (IC) engine results from the hot gaseous products of combustion acting on moving surfaces of the engine, such as the face of a piston, a turbine blade, or a nozzle. Combustion, also known as burning, is the basic chemical process of releasing energy from a fuel and air mixture. In an internal combustion engine (ICE), the ignition and combustion of the fuel occurs within the engine itself. The engine then partially converts the energy from the combustion to work. The engine consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. Ultimately, through a system of gears in the powertrain, this motion drives the vehicle’s wheels. This book is measurement and testing of engines explained with modern techniques using computers, mathematical modeling and electronic instrumentation.