Audiworld: The Direct-Injection Petrol Engine

IAA 2001: FSI - The Direct-Injection Petrol Engine Text and pictures courtesy of Audi AG To develop a new motor-vehicle engine is, generally speaking, to be faced with a difficult decision. In a nutshell, this is 'more power or less fuel' - a conflict of objectives as old as the spark-ignition engine itself and one that has lost almost none of its complexity, despite ongoing technical progress. Audi is now presenting a new generation of engines that makes a quantum leap in terms of operating efficiency: the FSI principle is opening up a new dimension for the spark-ignition engine. This is a step forward in technology that justifies comparison with the introduction of TDI technology for diesel engines. That too, in its day, succeeded in combining high power output and an effective reduction in fuel consumption to a previously unattainable extent. What can the FSI engine, in which petrol is injected directly into the cylinders, do better than a conventional engine with fuel injection into the intake ports? # The answer is: It is distinctly more dynamic, # Both its torque and power output are higher, # Yet fuel consumption is simultaneously as much as 15 percent lower. The main factor contributing to these improvements is the stratified charge principle at part load. In this operating mode, the engine only needs a fuel-air mixture capable of immediate ignition in the area around the spark plug. The remainder of the combustion chamber is filled with a leaner mixture, that is to say one with a considerable degree of excess air. As a result of this, the engine can be run without the incoming mixture flow being throttled. The direct-injection engine also benefits from reduced heat losses, because the layer of air around the 'cloud' of ignitable mixture isolates the latter from the cylinder and cylinde