Prakash, A., Nelson, E., Jones, A., Macias, J. et al., "Particulate Mass Reduction and Clean-up of DISI Injector Deposits via Novel Fuels Additive Technology," SAE Technical Paper 2014-01-2847, 2014, doi:10.4271/2014-01-2847.
Particulate mass (PM) emissions from DISI engines can be reduced via fuels additive technology that facilitates injector deposit clean-up. A significant drawback of DISI engines is that they can have higher particulate matter emissions than PFI gasoline engines. Soot formation in general is dependent on the air-fuel ratio, combustion chamber temperature and the chemical structure and thermo-physical properties of the fuel. In this regard, PM emissions and DISI injector deposit clean-up were studied in three identical high sales-volume vehicles. The tests compared the effects of a fuel (Fuel A) containing a market generic additive at lowest additive concentration (LAC) against a fuel formulated with a novel additive technology (Fuel B). The fuels compared had an anti-knock index value of 87 containing up to 10% ethanol. The vehicles were run on Fuel A for 20,000 miles followed by 5,000 miles on Fuel B using a chassis dynamometer. It was observed that Fuel A gave rise to an increase in PM emissions indicative of DISI injector deposit build-up. Whereas, Fuel B showed statistically significant reduction in PM emissions for all three vehicles at 95% confidence interval. PM reduction data was also supported by scanning electron microscope (SEM) images that showed clean-up of the injector deposits around the nozzle holes. The results observed are attributed to the thermal stability and the dosage of the additive technology utilized.