Hybrid analytical-experimental method to map power losses of automotive transmissions over their operating range

This work presents a hybrid analytical-experimental method for determining overall power losses of automotive transmissions. The method consists of measuring load-independent losses and calculating load-dependent losses. Measurements and calculations are done at selected combinations of torque and rotational speed. The results are used for computing the coefficients of a quadratic equation that describes a best-fit surface. The equation is used for predicting the transmission power losses over the operating range defining a transmission efficiency map. The method was verified against power loss measurements of a light-duty six-speed automotive transmission showing a strong correlation between predictions and measurements. The proposed method can be used as an engineering tool to help drive improvements in transmission efficiency and in fuel economy.