Parametric Calculation and Significance of Engine Dynamic Torque in Performance Benchmarking of a Vehicle

The automotive industries around the world is undergoing massive transformation towards identifying technological capabilities to improve vehicle performance. In this regard, the engine dynamic torque plays a crucial role in defining the transient performance and drivability of a vehicle. Moreover, the dynamic torque is used as a visualization parameter in performance prediction of a vehicle to set the right engineering targets and to assess the engine potential. Hence, an accurate measurement and prediction of the engine dynamic torque is required. However, there are very few methodologies available to measure the engine dynamic torque with reasonable accuracy and minimum efforts. The measurement of engine brake torque using a torque transducer is one of the potential methods. However, it requires a lot of effort and time to instrument the vehicle. It is also possible to back-calculate the engine torque based on fuel injection quantity and other known engine parameters. Though this calculation method is relatively easy, it is not an accurate method. Moreover, it would not be possible to extract engine information of benchmark vehicles. Since every method has their own capabilities, limitations and none of them are effective to capture real transient torque behaviour of an engine, this work elaborates about a distinct methodology to calculate dynamic torque and its role in performance prediction and benchmarking of a vehicle with reduced effort and time. In this method, dynamic torque of an engine is counter calculated from vehicle speed at individual gears taking inertial resistance into account along with drag force, driveline ratios and efficiency. Calculated dynamic torque is given as input to vehicle system simulation software. Corresponding performance number arrived from the vehicle model is validated with the experimental test results. The outcomes are found to have excellent correlation which makes this approach efficient and executable for better prediction of performance and selection of appropriate drivetrain configuration in early developmental stage of a vehicle. Moreover, this approach can be used for assessing the dynamic torque of benchmark vehicles too.