Fuel Economy Improvements in an SUV Equipped with an Integrated Starter Generator 2001-01-2825

North American sales of light duty trucks, including sport utility vehicles (SUV's), have now passed the 50% mark of total vehicles sold. This fact, along with the recent surge in gas prices, has drawn attention to the lower average fuel economy of this vehicle class. With possible changes to the light duty truck corporate average fuel economy (CAFE) standards looming on the horizon, vehicle manufacturers are looking for ways to improve the fuel economy of these vehicles without affecting performance or utility. One possible solution in accomplishing this objective is the 42 volt integrated starter-generator (ISG). The ISG offers the ability to reduce fuel consumption through the use of engine-off during coast-down and idle, early torque converter lockup with torque smoothing, regenerative braking, and electrical launch assist. It also boosts the onboard power generation and energy storage, allowing for increased vehicle electrical loads. Conservative estimates using vehicle simulation models have shown the potential fuel savings to be as much as 5-7% over the FTP -75 driving schedule from stop-start functionality alone.

This paper will detail the fuel economy benefits offered to SUV's having an engine stop-start function implemented with an ISG. Dynamometer test results for a Ford Explorer equipped with a Delphi-designed Energen-10® ISG are presented. A comparison is made to the results of Delphi-enhanced ADVISOR®▿ vehicle simulations. A strong correlation is shown between the two sets of results.