The Effects of Intake Valve Detergent Structure on Combustion Chamber Deposits (CCD) 952449
Combustion chamber deposits (CCD) have been heavily researched in the past with regard to Octane Requirement Increase (ORI). New concerns about their role in combustion chamber deposit interference (CCDI) and their potential contribution to exhaust emissions have reinforced interest in defining the underlying factors that contribute to CCD. In this study, intake valve detergents were evaluated in the absence of any fluidizer in L-6 1987 BMW 325e engines using 10,000 mile tests run with a BMW IVD driving cycle. The chemical structure of detergents used to reduce Intake Valve Deposits (IVD) has been systematically varied to determine its effect on the quantity and the composition of CCD. In general, chemical changes in the intake valve detergent had little effect on the amount and chemical composition of CCD. The composition of CCD was determined by X-ray Photoelectron Spectroscopy (XPS). All CCDs produced with fuels containing intake valve detergents showed the same types and similar levels of organic oxygen, sulfur and aromatic carbon. The CCDs did not contain intact additive backbone fragments or detergent head groups. The only distinguishing feature of these CCDs was the varying nitrogen content that appeared to depend on the type and number of amine groups in the detergent. However, the types of nitrogen present in the CCDs were chemically different from those present in the initial detergent suggesting that, although some of the nitrogen in the detergent head group remains in the CCD, it is chemically transformed.