INTRODUCTION An engine map is used to represent tested engine performance (fuel consumption, emissions, etc.) in a vehicle simulation in order to estimate drive cycle performance of the engine and vehicle [ 2, 3, 4]. The map is defined by triplets of engine speed, engine torque, and an engine performance parameter, for example brake specific fuel consumption. Figure 1 shows a schematic of the typical process to create such a map. An engine is run at steady speed and load conditions for some amount of time (usually minutes) for stabilization and data acquisition. After data collection at one point, the speed and load are ramped to another steady condition and the process repeated. The number of points varies depending on the intended use of the map, but can be over 100. Figure 2 shows an example map. Figure 3 shows how the map is used as part of a vehicle simulation, with each simulation time step using the map to predict instantaneous fuel consumption based on the current speed and load.An Engine and Powertrain Mapping Approach for Simulation of Vehicle CO2 Emissions Gary Salemme Cummins Inc. Erik Dykes Eaton Daniel Kieffer PACCAR Inc Michael Howenstein Allison Transmission Inc Matthew Hunkler Navistar Manik Narula Cummins Inc. ABSTRACT Simulations used to estimate carbon dioxide (CO2) emissions and fuel consumption of medium- and heavy-duty vehicles over prescribed drive cycles often employ engine fuel maps consisting of engine measurements at numerous steady-state operating conditions. However, simulating the engine in this way has limitations as engine controls become more complex, particularly when attempting to use steady-state measurements to represent transient operation. This paper explores an alternative approach to vehicle simulation that uses a “cycle average” engine map rather than a steady state engine fuel map. The map contains engine CO 2 values measured on an engine dynamometer on cycles derived from vehicle drive cycles for a range of generic vehicles. A similar cycle average mapping approach is developed for a powertrain (engine and transmission) in order to show the specific CO 2 improvements due to powertrain optimization that would not be recognized in other approaches. While a related paper [ 1] focuses primarily on simulation results, this paper summarizes the associated experimental results and development of the concept. Test results for an engine and a powertrain demonstrate the cycle average map is a smooth, continuous surface. The paper also compares accuracy of using the steady-state engine map versus the cycle average engine map. Considerations for using the cycle average map for vehicle simulation in the context of CO 2 regulations are also discussed with the conclusion that the cycle average map appears to be a technically viable approach to utilizing engine fuel consumption performance in a vehicle regulation. CITATION: Salemme, G., Dykes, E., Kieffer, D., Howenstein, M. et al., "An Engine and Powertrain Mapping Approach for Simulation of Vehicle CO2 Emissions," SAE Int. J. Commer. Veh. 8(2):2015, doi:10.4271/2015-01-2777.2015-01-2777 Published 09/29/2015 Copyright © 2015 SAE International doi:10.4271/2015-01-2777 saecomveh.saejournals.org 440Downloaded from SAE International by University of Liverpool, Monday, August 13, 2018Figure 1. Typical steady state map generation process Figure 2. Steady state BSFC map for the 2017 15 L 455 HP engine used in GEM Figure 3. Process for using a steady state BSFC map in a vehicle simulation This map can be used in a vehicle simulation for general vehicle performance understanding as well as powertrain matching of the engine, transmission, rear axle ratio, and tire size to the vehicle. Historically, the engine map approach has also been a reasonable method to predict vehicle drive cycle fuel consumption [ 2, 3]. However, there are some inherent assumptions in using an engine map in this manner: • The test cell engine installation mimics the ve