Knock Control Based on Engine Acoustic Emissions: Calibration and Implementation in an Engine Control Unit

In modern turbocharged downsized GDI engines the achievement of maximum thermal efficiency is precluded by the occurrence of knock. In-cylinder pressure sensors give the best performance in terms of abnormal combustion detection, but they are affected by long term reliability issues and still constitute a considerable part of the entire engine management system cost. To overcome these problems, knock control strategies based on engine block vibrations or ionization current signals have been developed and are widely used in production control units. Furthermore, previous works have shown that engine sound emissions can be real-time processed to provide the engine management system with control-related information such as turbocharger rotational speed and knock intensity, demonstrating the possibility of using a multi-function device to replace several sensors. In this paper, an innovative knock controller based on engine sound emissions is assessed by real-time implementation of the algorithm in a standard Engine Control Unit. The effectiveness of the technology has been proved by closing the spark advance control loop on a turbocharged GDI engine, and by comparing the controller performance with the traditional accelerometer-based system.