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It is easier and more economical to conduct R49 13-mode cycle emission tests in engine test bed compared to chassis dynamometer ECE R83 test. This is because of costlier test equipment for chassis dynamometer and requirement of separate dynamometers for various categories of vehicles, even when connected with the same engine. Two methods have been attempted for predicting ECE R 83 cycle emissions from R49 test results based on the extensive emission trials conducted in both engine and chassis dynamometers. The first method is by using the modified weightage factors applied to each mode results of R49 test. While the second method uses the mapped ECE R 83 load/speed points for a particular configuration of vehicle and translating them to nearest load/speed point of R49 cycle. The predicted emission values conform well to the actual chassis dynamometer results.

This paper describes the engine mapping work carried out on a 2.1 litre carburetted petrol engine.The purpose of this work was to improve upon the emission levels of the engine to meet 1996 emission norms with sufficient margin and to achieve best fuel economy possible. This paper deals with the strategy for the selection of speed load points required for mapping depending on engine operating zones, engine base data collection, methodology followed in engine mapping, variation of engine performance and emissions with respect to air/fuel ratio and spark timing etc. Further the mass emission predictions for different strategies like leaning the air/fuel mixture, retarding the ignition timing etc. are also discussed. Recalibration of the carburettor based on the above findings, its effect on vehicle performance are dealt with.