Full load performance optimization based on turbocharger speed evaluation via acoustic sensing

Turbocharger performance optimization on passenger car engines is particularly challenging, especially in case of severe engine downsizing and downspeeding. On high performance engines (e.g., heavy duty truck applications) turbocharger speed measurement is usually performed with the aim of maximizing engine power and torque, limiting turbocharger over-speed, which is harmful for its durability and reliability. This solution is too expensive for passenger cars, and the turbocharger speed sensor is typically not available. In this work, an innovative and low cost sensing chain for the rotational speed evaluation of the turbocharger is applied. With this information, obtained via an acoustic sensor, a new turbocharger control architecture has been developed to optimize turbocharger performance, in order to improve engine output torque under full load conditions. After a brief description of the new sensing chain and of the electronic components developed to manage this kind of information, the paper shows the new control architecture that takes advantage of the turbocharger speed information. Moreover, experimental results on a small turbocharged Diesel engine for passenger car applications are presented, demonstrating the achieved benefits.