The influence of gear change on vehicle exhaust emissions. Calculations with the vetess emission tool

Abstract

This study explores the influence of gear changing behaviour on vehicular exhaust emissions and fuel consumption using the emission simulation tool VeTESS (Vehicle Transient Emissions Simulation Software). VeTESS was used to assess the impact of (not) changing gear at certain vehicle speeds on the exhaust of vehicle air pollutants using theoretical drive cycles as input. The hypothesis formulated is that, by selecting a higher gear early, one will avoid high engine speeds and achieve a reduction of emissions and fuel consumption. Calculations to test this hypothesis were executed for two vehicles of the Belgian fleet: a Euro III diesel car and a EURO IV petrol car. The results for CO2, CO and HC confirm the hypothesis and show that one can save fuel and decrease vehicle exhaust emissions by changing up gear. The results for NOx and PM, on the other hand, differ slightly.