Injector nozzle deposits can have a profound effect on particulate emissions from vehicles fitted with Gasoline Direct Injection (GDI) engines. Several recent publications acknowledge the benefits of using Deposit Control Additives (DCA) to maintain or restore injector cleanliness and in turn minimise particulates, but others claim that high levels of DCA could have detrimental effects due to the direct contribution of DCA to particulates, that outweigh the benefits of injector cleanliness.
Much of the aforementioned work was conducted in laboratory scenarios with model fuels. In this investigation a fleet of 7 used GDI vehicles were taken from the field to determine the net impact of DCAs on particulates in real-world scenarios. The vehicles tested comprised a range of vehicles from different manufacturers that were certified to Euro 5 and Euro 6 emissions standards. In a first phase, the vehicles were fuelled on EN228 compliant gasoline treated with a high dose of DCA and were driven on a chassis dynamometer over 4750km and in two cases over 5800km with periodic WLTC emissions measurements to determine the potential for particulate emissions and fuel consumption and CO2 reduction attributable to injector clean-up.
In a second phase, a series of WLTC tests were conducted while the fuel was alternated between the high-DCA fuel and the same fuel excluding the DCA to determine the instantaneous effect of the DCA on particulate emissions.
A fleet-average reduction in particulate emissions, fuel consumption and tailpipe CO2 emissions were observed with the continuous use of high-DCA fuel whereas no statistically significant differences were observed from the tests alternating between the high-DCA and unadditivated fuels. Therefore, the injector cleanliness benefits of operating these real-world vehicles on high-DCA fuel far exceeded any detriments due to the instantaneous impact of the DCA.