Gasoline Direct Injection (GDI) vehicles now make up the majority of European new car sales and a significant share of the existing car parc.
Despite delivering measurable engine efficiency benefits, GDI fuel systems are not without issues. Fuel injectors are susceptible to the formation of deposits in and around the injector nozzles holes. It is widely reported that these deposits can affect engine performance and that different fuels can alleviate the buildup of those deposits.
This project aims to understand the underlying mechanisms of how deposit formation ultimately leads to a reduction in vehicle performance. Ten GDI fuel injectors, with differing levels of coking were taken from engine testing and consumer vehicles and compared using a range of imaging and engine tests.
At the time of writing, a new GDI engine test is being developed by the Co-ordinating European Council (CEC) to be used by the fuel and fuel additive industry. One such test was used to precondition six of the injectors in this study. It was found that injectors run in this test without additives experienced significant deposit formation. The use of fuel with Deposit Control Additives (DCA) was found to reverse that effect.
This study builds significantly on an earlier paper (SAE 2019-28-2392), adding data from more injectors and single cylinder engine testing. This additional content brings new insights and helps to put that earlier work into greater context.
The CEC test is a well-controlled steady state test, which allowed a straightforward comparison of the different injectors. Despite only being a steady state test, the test point of 2000rpm / 56Nm was considered realistic and one that occurs regularly in real driving and vehicle emissions testing.