The Independent Effect of Mid-Range, Back-End Volatility And Aromatics on Emissions from Two European Gasoline Engines

A set of designed fuels was tested in two European gasoline vehicles driven over the standard European Drive Cycle. Both regulated and speciated emissions were measured, together with HC, CO and NOx, pre- and post-catalyst.

The main fuel set was a 3 by 3 matrix, where mid-range volatility (T50) and aromatics were independently varied from 85°C to 115°C for T50 and from 25% vol. to 45% vol. for aromatics. Two further fuels, together with the centre point fuel from the main matrix, formed a back-end volatility (T90) subset experiment. The fuels were blended from mixtures of pure chemicals in order that the chemical and physical properties could be closely controlled and kept independent.

The findings of this two car trial are generally in line with the recent EPEFE programme and confirm that fuel changes which reduce one type of emissions (HC and CO) generally increase another (NOx) and vice versa. The study has also highlighted the importance of engine management and catalyst operation in determining emissions, in particular the important role of small variations in stoichiometry (F). Further, this study has shown that engine system technology influenced the vehicle's response to changes in fuel properties.