Energy Conversion Factor for Gasoline Engines in Real-World Driving Emission Cycle

A precise energy conversion factor is required to define the impact of greenhouse gas emissions by gasoline-powered vehicles and policies that will guide the application of future eco-innovations. The current energy conversion factor adopted by many countries is based on the Willans line approach, initially proposed in 1888 for steam engines, later adapted for internal combustion engines. The actual energy conversion factor, which defines the energy conversion for drivers in real traffic, is missing. In this article, eight world-class engines are tested in an engine bench for the acquisition of specific fuel consumption 3D maps. Then, their energy conversion factors, calculated by dividing the energy output by the energy input, are simulated in real and urban traffic, acquired according to the real driving emissions (RDE) cycle. In addition, a reference vehicle is instrumented to measure the energy input (fuel flow) and the energy output (mechanical energy in the half axles) under the same RDE cycle standards. The results of both procedures are very similar, respectively, 0.405 ± 0.04 L/kWh for the simulation based on eight benchmark engines, and 0.392 ± 0.04 L/kWh for the reference vehicle driven in RDE traffic conditions, with a 95% confidence interval. For turbocharged engines, the factor attained by the simulation is 0.395 ± 0.04 L/kWh. The values of the energy conversion factor for gasoline engines got in this research are higher than those obtained through the Willans line approach, suggesting a new standard value of 0.405 L/kWh, replacing the current 0.264 L/kWh. It could substantially change the greenhouse gas emissions in a tank-to-wheel approach for the entire vehicle and add-on eco-innovations.