A Study of Fuel Additives for Direct Injection Gasoline (DIG) Injector Deposit Control 2000-01-2020

We report on a comprehensive fuel additive study where two different detergent chemistry types, Mannichs and polyetheramines, are ranked with regard to injector deposit control in a research direct-injected gasoline (DIG) engine. The engine used was a conventional dual-sparkplug, 2.2-liter Nissan engine modified for direct injection using one of the sparkplug holes. The engine was run under 20% rich conditions to accelerate injector deposit formation. The two detergent chemistry types are shown to perform quite differently with the Mannichs showing superior performance. The Mannich detergent chemistries can reduce the DIG injector flow loss after using Howell EEE fuel from a high of 11.23% to a low of 3.14% whereas the best polyetheramine detergent chemistry tested reduced it to 8.17%. One of the Mannichs was further tested in a year 2000 specification gasoline with 150 ppm sulfur, and a North American type gasoline with 420 ppm sulfur. The detergent lowered the flow loss from 6.67% to 1.66% in the former and from 10.36% to 4.5% in the latter fuel. Clean-up was observed with a Mannich detergent when used at a clean-up treat rate. Flow recovery from a dirty-up level of 9.25% flow loss to a more modest flow loss of 2.77% was observed, a clean-up of 70%. The kinetics of deposit build-up and the role of gasoline detergent additives in controlling this build-up are outlined. A mathematical model to describe the observed kinetics was developed and found to fit the experimental data very well.