Direct injection spark ignition (DISI) engine technology offers tremendous potential advantages in fuel savings and is likely to command a progressively increasing share of the European passenger vehicle market in the future. A concern is its propensity to form deposits on the inlet valve. In extreme cases, these deposits can lead to poor drivability and deteriorating emission performance. This inlet valve deposit build up is a well-known phenomenon in DISI engines since even additised fuel cannot wash over the back of intake valves to keep them clean.
Two lubricants and two fuels were tested in a four car matrix. One of the lubricants was a fluid specifically developed by Lubrizol for DISI technology; the other was a baseline oil meeting Ford lubricants requirements and was qualified to ACEA A1/B1/ ILSAC GF2 performance level. Similarly, a baseline fuel was tested against an additised system. A test cycle was devised to accumulate deposits over a 30.000km oil drain interval and was conducted at an independent vehicle test track facility.
The primary purpose of the program was to investigate the impact of lubricant and fuel on engine deposits, particularly intake valve deposits (IVDs) and combustion chamber deposits (CCDs). Additional parameters such as piston deposits (PDs), engine wear, engine sludge, injector deposits, driveability and used oil condition were measured.
The project clearly demonstrated that lubricant formulation has a significant impact on the level of IVD formation. There are indications that the additised fuel may also have had a beneficial impact on IVDs. The field test program also showed that despite the build up of deposits on the intake valves over the 30.000km test no detrimental effect on drivability was experienced with the Ford DISI engine technology. This paper explains the testing carried out and quantifies the improvements established.