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Worldwide concern about combustion chamber deposits (CCDs) has increased from the viewpoint of fuel and additives technology, which has been developed for the cleaning of intake valve deposits (IVDs), intake port deposits and injector deposits. The research effort described here, focused on the differences between CCDs and IVDs in terms of quality based on analyses of CCDs and IVDs collected from used vehicles from the Japanese market. The CCDs and IVDs were characterized according to weight, benzene-solubles and sulfated ash. Since the sulfated ash in CCDs is a key to understanding the effect of engine oil on CCD formation, the relationship between CCDs and the sulfated ash in CCDs was evaluated under the two typical conditions on a 2.0L engine testing bench. Based on the results, the gasoline-related and oil-related factors were estimated for these conditions. Moreover, the effect of CCDs on exhaust emissions was investigated in a 2.2L vehicle.

The effects of gasoline volatility (T50 and T90), sulfur content and hydrocarbon types on CO, NOx, total hydrocarbon and speciated hydrocarbons were investigated. The properties of the test gasoline were varied in the range of the Japanese marketplace gasoline, which are characterized by low T50, T90 and low sulfur content. Sulfur content is, especially, regulated under 100 ppm. The Japanese 10.15 mode emissions under hot-transient conditions were measured by using a vehicle equipped with a three-way catalyst. The results indicated that the sulfur content was more effective on exhaust CO, total hydrocarbon and NOx emissions than T50, T90 or hydrocarbon types of gasoline were. The sensitivity to sulfur was different depending on the speciated hydrocarbons. Increasing the sulfur content significantly raised exhaust paraffines, but had no significant effect on olefins. Among the aromatics, the exhaust benzene was most sensitive to sulfur.