Hakeem, M., Surnilla, G., Shelby, M., House, C. et al., "Evaluating the Benefits of On-Board Measurement of Ambient Humidity Part-2: Effect on Torque Estimation Accuracy and Drivability," SAE Technical Paper 2016-01-1068, 2016, doi:10.4271/2016-01-1068.
Engine Mapping is usually performed under nominal conditions which include a humidity level of 8 g/Kg. Customers driving at different humidity conditions (which may range from 1 g/Kg in dry and colder climates and up to 35 g/Kg as in tropical climates) may experience a degraded performance due to the errors in engine torque estimation provided by the ECU. The torque estimation error interacts with many other features that affect drivability, such as the peak performance of the engine, transmission shift quality, etc.This paper extends the investigation in Part-1 by analyzing and quantifying the torque estimation error that may result in certain customer use cases at high humidity conditions, due to the mismatch between calibrated and actual conditions. The analysis is mainly performed for Speed-Density systems (MAP sensor based) but the effect of mass air flow sensor (MAF sensor) based systems is also briefly considered. Dyno tests were utilized to evaluate the change in ECU estimated torque when humidity compensation is enabled and disabled, in addition to the actual torque delivered by the engine for the same driver request.Compensating for humidity was shown to improve the torque estimation of MAP based systems by 4-10%, with the highest benefit observed at high BMEP points. Moreover, the torque delivery and control were improved by 5-6%. For MAF systems, an error of 8% was noted at lower BMEP points.