Resumen
A fleet of 9 two-wheelers (5 mopeds and 4 motorcycles) was tested in the Vehicle Emissions Laboratory of the European Commission Joint Research Centre to evaluate the effect of several tampering procedures on the tailpipe exhaust emissions. Vehicles performed prescribed driving cycles (ECE-R47 and WMTC) on a chassis dynamometer in a climatic test cell, and raw as well as diluted emissions were collected, the latter following the European legislation. After testing the vehicles in their original configuration, an intrusive tampering was applied and tests were repeated for comparison of the results. We found that the impact of tampering is vehicle- and compound-specific with a prevalence of negative effects on the exhaust emissions (regulated and unregulated). Remarkably in some cases, the tampering for improved vehicles? performance increased the total hydrocarbons and carbon monoxide up to 27 and 15 times with respect to the original vehicles in hot engine conditions. Nitrogen oxides increased up to a factor of 2 when the tampering involved the intake air or hotter/leaner engine conditions. The results for unregulated compounds included ammonia (up to a 30 fold increase), nitrogen dioxide (up to 11 times), nitrous oxide (up to 2.5 times), acetaldehyde (up to 2.4 times), formaldehyde (up to 4 times), ethanol (up to 3.4 times) and aromatic compounds (up to 2 times). We show that tampering aimed at improving the vehicle's performance can have deleterious effects on the exhaust emissions, thus posing serious concerns on air quality.