The Effect of Diesel Density, Injection Technology and External Variables on the Acceleration Performance of Modern Passenger Cars

Diesel engines operate with an open-loop fuel control system and the engine torque is therefore affected by variations in the fuel density. Five vehicles, representing a range of different injection technologies, were tested on six fuels having densities ranging from 819.5 to 840.1 kg/m³ @ 15°C. The results indicated that rotary distributor-pump systems were considerably more sensitive to fuel density variations than the common-rail systems or unit-injectors. The fuel density variations caused acceleration performance deviations ranging over 7%. Various external factors (vehicle loading, air conditioner, under-inflated tires, open windows, headwinds, road gradients and different road surfaces) caused deviations in the acceleration performance of comparable magnitudes.