INTRODUCTION Increasing powertrain efficiency is a primary path manufacturers have available for reducing fuel consumption (and thus GHG emissions). In general, increasing powertrain efficiency can be accomplished by increasing engine efficiency, increasing transmission efficiency, or altering transmission shift strategy so the engine operates nearer its peak efficiency more often. Transmission technology is a significant portion of the potential reduction in fuel usage for advanced vehicles. Automatic transmission systems can be altered to • Contain more gears with a wider gear ratio span, allowing the engine to operate closer to its peak efficiency more often. • Upshift earlier, so the engine operates in a more efficient portion of its map when possible. • Lock up the torque converter earlier, resulting in fewer losses in the torque converter. • Reduce frictional and other energy losses in the transmission itself. Previous studies have estimated a range of potential reduction in fuel usage. For example, Argonne National Labs (ANL) examined the potential reduction in fuel consumption when installing an advanced transmission in a midsized vehicle equipped with a four-cylinder spark ignited direct injection (SIDI) engine. [ 1] The study predicted a 6.9% improvement in fuel consumption when comparing a 96% efficient eight-speed automatic transmission with early torque converter (TC) lockup to a 92% efficient five-speed transmission without early TC lockup. For a port fuel injected (PFI) engine, the same transmission comparison yielded a 9.0% improvement in fuel consumption. [ 2] Likewise, the National Research Council (NRC) investigated the potential effects of advanced transmissions on fuel economy in their 2015 report. [ 3] They examined the potential reduction in fuel Investigating the Effect of Advanced Automatic Transmissions on Fuel Consumption Using Vehicle Testing and Modeling Andrew Moskalik, Aaron Hula, Daniel Barba, and John Kargul US Environmental Protection Agency ABSTRACT In preparation for the midterm evaluation (MTE) of the 2022-2025 Light-Duty Greenhouse Gas (LD GHG) emissions standards, the Environmental Protection Agency (EPA) is refining and revalidating their Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) tool using newly acquired data from model year 2013-2015 engines and vehicles. ALPHA is a physics-based, forward- looking, full vehicle computer simulation capable of analyzing various vehicle types with dif ferent powertrain technologies, showing realistic vehicle behavior, and auditing of all internal energy flows in the model. As part of the validation of ALPHA, the EPA obtained model year 2014 Dodge Chargers equipped with 3.6 liter V6 engines and either a NAG1 five-speed automatic transmission or an 845RE eight-speed automatic transmission. Vehicles were tested on a chassis dynamometer; test results showed eight-speed vehicles averaging 6.5% reduction in unadjusted combined city-highway fuel consumption compared to five-speed vehicles. In addition, an 845RE eight-speed transmission was obtained and tested in a standalone transmission test rig. The measured transmission parameters were used in ALPHA to simulate the behavior and fuel consumption of the eight-speed Dodge Charger. A companion model for the five-speed Charger was also constructed; the resulting simulated fuel consumption for both vehicles closely matched the test results. This paper uses the validated ALPHA model to predict the effectiveness improvement of real-world transmissions over a baseline circa 2008 four-speed transmission, and to predict further improvements possible from future eight-speed transmissions. To that end, transmission models for a four-speed automatic transmission and future eight-speed automatic transmissions were constructed, and ALPHA was used to predict the fuel consumption differences of a Dodge Charger equipped with these transmissions. A fuel consumption reductio