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Exhaust emission and fuel consumption of a vehicle is influenced by its usage, operating conditions, traffic conditions as well as the individual behaviour of the driver. A study on the actual operating conditions for city buses has been carried out for Delhi city under a Government sponsored Project by The Automotive Research Association of India (ARAI). A bus operating on the normal city route was selected and equipped with sensors and data acquisition systems to record the vehicle parameters such as vehicle speed, distance, time, gear shifting pattern, engine speed, temperatures and other variables every second. The data collection exercise was carried out on six selected routes covering lean, average and peak periods of traffic and vehicle density. Earlier experience shows that data thus collected can be synthesised to fall into statistical repetitive driving sequences. This averaged data is converted into a most logical driving pattern or cycle for buses operating in Delhi city.

Two carburetted passenger cars of different makes, converted for CNG (Compressed Natural Gas) operation (in dual mode) and optimised by ARAI (The Automotive Research Association of India, Pune, India), were tested for vehicular performance. The respective engines were also mapped for performance, energy consumption and emission. The power loss in CNG mode was 7% & 15% and torque reduction was 21% & 15% in respective engines. There is considerable improvement in thermal efficiency and reduction of emission in the entire operating range. The vehicle performance on Chassis Dynamometer shows similar results. The second engine was also tested with a ceramic catalytic converter which gave 93% reduction in CO and 50% reduction in HC in major portion of operating range. 1100 CC car was also tested on the test track. Optimisation work included installation of ARAI mixer design.

Development works with metallic open channel PM Filter Catalyst in conjunction with diesel oxidation catalysts and Pre Turbo Catalyst (PTC) on Diesel Cars and Commercial Vehicles with CRDi engines have been reported earlier. These results show that PM conversion efficiency of the order of 40 % can be achieved with PM Filter Catalyst on passenger car diesel engines with continuous regeneration capability. Recently experiments were carried out on a DI engine having distributor type rotary fuel injection equipment with electronic control, turbocharged and inter-cooled, calibrated for BS-III (EURO-III) emissions, with an aim to explore the potential of oxidation catalyst and the PM Filter Catalyst to meet BS-IV (Euro-IV) emission norms. These experiments were carried out with 500ppm sulphur diesel. The results of the tests are presented in this paper. It is seen that with only an oxicat of low level catalyst loading, PM (soluble organic fraction) can be brought down by 20%.