Estimated engine torque is an important parameter used by automotive systems for automated transmission and clutch control. Heavy-duty engine and transmission manufacturers widely use SAE J -1939 based ECU torque calculation based on mass air/fuel flow steady state maps created during calibration of the engine for this purpose. As an alternative, to enhance the accuracy of this important control variable, a virtual flywheel torque sensor (VFTS) was developed. It measures the engine torque based on the harmonics of the instantaneous flywheel speed signal. Initial dynamometer testing showed the VFTS estimated torque values exhibited a maximum inaccuracy of 12% of the actual measured torque over the range of conditions tested. In this paper we report the results of on road truck testing of the VFTS. A loaded heavy truck with a gross vehicle weight rating of 80,000 pounds was used. The performance of the VFTS was tested in different gears at full throttle in the diesel engine speed range of 1000 RPM to 1900 RPM. The accuracy of the VFTS sensor is found to vary with gear ratio, depending on the speed and road conditions. The VFTS showed better accuracy in higher gears than in lower gears. Further, an AMEsim truck drivetrain dynamic modelling was performed for comparing and analyzing the performance of the VFTS with test results under different load and speed conditions in different gears. These results showed good agreement between the simulation and experiment at full throttle in high gears.
