Vehicle Inertia Impact on Fuel Consumption of Conventional and Hybrid Electric Vehicles Using Acceleration and Coast Driving Strategy

In the past few years, the price of petroleum based fuels, especially vehicle fuels such as gasoline and diesel, have been increasing at a significant rate. Consequently, there is much more consumer interest related to reducing fuel consumption of conventional and hybrid electric vehicles (HEVs). The “pulse and glide” (PnG) driving strategy is first applied to a conventional vehicle to quantify the fuel consumption benefits when compared to steady state speed (cruising) conditions over the same time and distance. Then an HEV is modeled and tested to investigate if a hybrid system can further reduce fuel consumption with the proposed strategy. Note that the HEV used in this study has the advantage that the engine can be automatically shut off below a certain speed (∼40 mph, 64 kph) at low loads, however a driver must shut off the engine manually in a conventional vehicle to apply this driving strategy. A general analysis of a pulse and glide (PnG) driving strategy is presented and the fuel energy benefit ratio is proposed. Simulation results of a Ford Focus show 33 - 77 % fuel economy improvement by the PnG driving strategy depending on different speed ranges and acceleration times. The fuel economy results of a 2004 Toyota Prius from simulation and testing show 24 - 90 % fuel economy improvement with PnG drive cycles compared to steady speed results. However, the fuel economy can vary in HEVs by electric only drive mode fraction during one short cycle, especially for steady speed cases. The change in battery SOC should be small to compare fuel use results correctly for HEVs.