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.
For both bench and road vehicles, CCD was monitored by measuring CCD thickness on the piston crown through the spark plug hole, together with measurements of the overall changes in CCD and IVD mass on completion of the test. Engine out emissions were measured continuously throughout each engine test and periodically during the road trials.
The results have established how CCD, NOx and fuel economy vary with time/mileage for both the M111 bench engine and for two models of road vehicles. Trends between CCD growth and the changes in NOx and fuel consumption were in broad agreement for both the engine tests and the road trials. These results increase the confidence in the M111 test as an effective means of not only measuring CCDs but also linking deposits to associated NOx emission changes.