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The Sources of Unburnt Hydrocarbon Emissions from Spark Ignition Engines during Cold Starts and Warm-Up

The results of a three-year collaborative research study into the sources of unburnt hydrocarbon (uHC) emissions are reported. The study sought to extend existing knowledge of the sources in an engine to the crucial period following a cold start and before the exhaust catalyst becomes fully effective. The study, carried out on a range of engines but centred on the Rover M 16 four-valve engine, identified a number of sources, all of which are equally important in the warm-up period. The paper concludes with some recommendations for the control of uHC emissions