Driven by recent legislative changes, the requirements for passenger car engines in terms of reduced pollutant emissions have increased. Standardised cycles are carried out, such as the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) on the dynamometer and real-life driving (RDE) tests. [1]–[3] Due to high costs for RDEs, an attempt is made to handle a large part of the emission tests on rolling test benches. The European average temperature is 14°C, with the WLTP at 23°C. [4] For better representation of test results, test rigs would have to be able to perform WLTPs at low temperatures. Due to the standards, most test benches are not equipped to provide cold air for the process. Retrofitting and installing conventional cooling systems are sprawling, costly and inefficient, so an innovative system is to be developed that expands pre-cooled and pre-compressed air on a radial turbine. Expanding can reach temperatures below freezing. In this work, a mathematical model adapted and modified from Aungier is provided for the predesign of the turbine. [5] Based on the results of the mean line model, the rotor, stator and volute of the turbomachinery had been modelled and tested in a CFD simulation using Ansys Fluent. Furthermore, methods are introduced to evaluate the design during the design procedure. Three test cases are provided to compare the results from the original case obtained with the mathematical model and two modifications.