The paper presents the development of a methodology for the evaluation of the Wide-Open-Throttle (WOT) torque production when the engine is running free. Under such conditions the engine speed shows a sudden increase due to the high engine torque production associated with the WOT conditions, and to the absence of a load connected to the engine. The acoustic emission of the engine contains information related to this speed increase and thus to the engine torque production.
The methodology unveils the information contained in the engine acoustic emission to estimate the torque produced under WOT operating conditions. This estimation can be performed without the need of coupling the engine to a brake, and does not require installing any additional sensor.
For this reason the approach here presented could be very useful for engine testing at the end of the assembly line. In fact, since the test to be performed is very fast and does not require to couple the engine to a brake, it allows to dramatically reduce the time needed for the testing procedure. This means cost reduction and the possibility to perform such testing procedure on all the produced engines.
Experimental tests have been performed in order to set-up the methodology on an L4 1.2 liter engine. The approach has been finally applied to the same engine, whose injection timing and spark advance were controlled to modify its torque production. The procedure showed a good capability to estimate WOT torque production, and to detect abnormal conditions that were induced by appropriately controlling injection and ignition.