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A European test procedure for evaluating engine deposits, using the Mercedes Benz M111 bench engine, has already been approved for inlet valve deposits (IVD) and is under development for combustion chamber deposits (CCD) by the Co-ordinating European Council (CEC). This paper describes CCD effects on emissions using a slightly modified version of this engine test procedure and compares it with CCD/emissions data from road vehicles. The engine used was a modern four valve, four cylinder, 2.0 litre passenger car unit and the bench test procedure used extended the operating time from the specified 60 hours to 180 hours. The road vehicle trial used two Mercedes Benz C200 passenger cars fitted with the M111 engine and two Ford Mondeo 2.0 litre passenger cars. Data was collected up to 11200km, approximately equivalent to 180 hours operation of the bench engine.

The influence of fuel quality on oxidation exhaust catalyst (OEC) efficiency in decreasing emissions of carbon monoxide, total hydrocarbons and total particulate matter (PM) from diesel cars has been investigated. Both in-house test results and further interpretation of published chassis dynamometer data have been utilised. Intrinsic OEC activity, which depends on exhaust gas temperatures, is shown to be largely unaffected by fuel quality, other than sulphur content. OECs affect PM emissions by changing the ratio of the soluble organic fraction to fixed carbon within engine-out PM. This ratio is strongly influenced by engine design and operation mode and to a lesser extent by fuel cetane number.