Drag Phenomena Within a Torque Converter Driven Automotive Transmission—Laminar Flow Approach

When discussing a torque converter driven, automotive transmission with respect to the vehicle’s coasting mode, automotive engineers have to take into account the slip between the converter’s propeller and turbine. If the turbine isn’t locked to the propeller during coasting process, drag phenomena within the converter’s fluid occur and they have to be properly assessed when computing the coasting process dynamics. The best way to make the needed evaluation is to have a separate torque converter and test it on a test bench, if the data provided by the manufacturer, in this respect, weren’t available. In the attempt to assess its’ coasting dynamic performances, we faced the problem of the reverse rotation of the torque converter that strongly influences the general drag of the vehicle’s motion. Hence, this paper tries to provide a method to determine the transmission overall drag considering the torque converter as being its main contributor. The method is based on the experimental research. This method can be successfully used for all type of hydrodynamic components of the transmission under the condition of developing the necessary experimental research. As far as the test were concerned, they were the typical ones designed to determine the mass inertial moments of the transmission components using the “falling weight” principle.