Influence of the stop/start system on CO2 emissions of a diesel vehicle in urban traffic

This paper presents measurements of CO2 emission and efficiency of stop/start technology on a diesel vehicle in urban traffic. Two four-wheel-drive diesel vehicles with on-board exhaust emission and vehicle activity measurement systems were tested in two urban driving circuits representative of downtown Madrid. The vehicles had similar turbocharged and intercooled diesel engines fulfilling the same Euro 4 emissions regulation; but one had an improved engine incorporating stop/start technology. CO2 emission reduction of more than 20% for the car equipped with the stop/start system was obtained. Regardless of the variability in driving style, the grade and type of streets, traffic congestion, and the engine operating temperature, the car equipped with the stop/start system has intrinsically a lower CO2 emission factor.

Research highlights
► Four-wheel-drive diesel vehicle fitted with a stop/star system have been tested.
► Significant CO2 emission reduction is found in congested urban traffic conditions.
► Statistical analysis was used to explain the variability observed in real traffic.
► Instantaneous tractive power was used to justify the improvement in the efficiency.