Impact on Reduction of Pollutant Emissions from Passenger Cars when Replacing Euro 4 with Euro 6d Diesel Engines Considering the Altitude Influence

The impact of Euro 4 compression ignition engines over the air quality in Europe has been analyzed in this work by comparing them with Euro 6d emissions regulation. The Euro 6d diesel engine has been chosen as the preferred replacement according to its advantages in global warming potential (GWP) emissions, like methane hydrocarbons (MHC) and CO 2 , with respect to Euro 6d petrol-based powertrains. The motivation for this study is that the effects of the emissions reduction policies, as the implementation of the regulation Euro 6d, are necessarily limited due to the great number of passenger cars still in circulation that were homologated under Euro 4 or older standards. To address the impact of the old vehicle pool, a Worldwide harmonized Light-vehicles Test Cycle (WLTC) has been used to analyze the performance and pollutant emissions of a Euro 4 diesel engine in altitude conditions. This driving cycle and engine are considered as a baseline for the subsequent discussion, where the altitude plays a key role because of the European geography. It forces passenger cars to drive over sea level during a significant number of trips. Thus, an analysis of how significant would be the impact of energy policies promoting the substitution of the pre-Euro 5 diesel fleet (>10 years old) by modern Euro 6d engines in the short term on the pollutants and GWP emissions reduction is presented.