In order to be ever more fuel efficient the use of Direct Injection (DI) is becoming standard in spark ignition engines. When associated with efficient turbochargers it has generated a significant increase in the overall performance of these engines. These hardware developments lead to increased stresses placed upon the fuel and the fuel injection system: for example injection pressures increased up to 400 bar, increased fuel and nozzle temperatures and contact with the flame in the combustion chamber.
DISI injectors are thus subjected to undesirable deposit formation which can have detrimental consequences on engine operation such as reduced power, EOBD (Engine On Board Diagnostics) issues, impaired driveability and increased particulate emissions. In order to evaluate the sensitivity of DI spark ignition engines to fuel-related injector deposit formation, a new engine test procedure has been developed.
In this paper the effects of gasoline composition on injector fouling are studied. The ability of the procedure to evaluate the performance of different Deposit Control Additives (DCAs) both in terms of reduction of deposits formation (keep-clean) and of deposits removal (clean-up) is also discussed. In a further aspect the influence of fuel variability on additive response is highlighted.