Deposits on engine parts, and in particular in combustion chambers of modern engines are causing increasing concern in the automobile industry. Highly sophisticated engine management systems make effects on emissions or performance obvious as outgassing of unburned hydrocarbons or variation of spark advance. Reduced mean heat flux away from the cylinder influences engine thermodynamics. Extreme deposits may cause noise increase by carbon rap. A special form of combustion chamber deposits, well known under the synonym spark plug fouling, is a carbon needle on spark plugs, which can cause the total damage of the catalysts (Japanese Industrial Standard D 1606: Adaptability Test Code of Spark Plug for Automobiles)
The Co-ordinating European Council for the development of performance tests for transportation fuels, lubricants, and other fluids (CEC) started the development of a new performance test in 1994. The objective was a combined test for intake valve and combustion chamber deposit evaluation.
This paper reflects and summarises a major part of the work that has been carried out by the CEC PF-020 working group and that is well documented within the CEC. During the development, the engine test conditions have been investigated and optimised, including the appropriate test length.
The test was then used to assess different base gasolines as well as the influence of additives and treat rates on deposit formation. The results show that also the future quality gasolines cause substantial intake valve and total combustion chamber deposits (IVDs and TCDs), which demonstrates the ongoing need for effective gasoline detergent additives. The results indicate that gasoline additives tend to increase TCD formation.
A comprehensive literature survey completes the paper.