Modeling of a Conventional Mid-Size Car with CVT Using ALPHA and Comparable Powertrain Technologies

The Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) tool was created by EPA to evaluate the Greenhouse Gas (GHG) emissions of Light-Duty (LD) vehicles [1]. ALPHA is a physics-based, forward-looking, full vehicle computer simulation capable of analyzing various vehicle types combined with different powertrain technologies. The software tool is a MATLAB/Simulink based desktop application. The ALPHA model has been updated from the previous version to include more realistic vehicle behavior and now includes internal auditing of all energy flows in the model [2]. As a result of the model refinements and in preparation for the mid-term evaluation (MTE) of the 2022-2025 LD GHG emissions standards, the model is being revalidated with newly acquired vehicle data.

In the effort to model the current and future US Light-Duty fleet there are times when complete and exact engine and powertrain component data are unavailable and must be approximated using components with comparable levels of performance and technology. This paper presents the testing and ALPHA modeling of a CVT-equipped 2013 Nissan Altima 2.5S using comparable powertrain technology inputs. A brief overview of recent improvements in CVT performance and efficiency is provided. ALPHA’s CVT shift strategy, ALPHAshift-CVT, is introduced and its performance is compared with data from the Altima. Fuel economy and carbon emissions results over a wide range of drive cycles were within 5% of measured values and the city/highway weighted combined fuel economy and carbon emissions were within approximately 1% of measured values, providing confidence in the proxy powertrain approach.