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Two wheelers, as a means of transportation, are a quandary to India's environment. The frugal use of gasoline on these vehicles provides economical transportation with low CO2 emissions. Unfortunately, the same engines tend to pollute the environment with high levels of unburned hydrocarbons (HC) and carbon monoxide (CO) emissions. To meet India's new environmental legislation, it will require an integration of catalytic elements within the exhaust system along with some engine modifications to achieve the most cost-effective solution. This paper will outline the current India two wheeler regulatory requirements along with the catalyst conditions and requirements for meeting the standards. Using an array of modeling tools, laboratory, dynamometer and vehicle testing, emission devices are developed for this purpose.

Catalytic control of motorcycle vehicle emissions requires that the catalytic element be carefully integrated into the exhaust system. The catalyst element physical parameters are optimized to achieve specific exhaust tuning requirements. Since the converter is located inside the muffler, the peak temperatures can severely stress both the catalytic active washcoat materials and the currently used metal monolith structure under some operating conditions. This paper addresses the development of an alternative ceramic monolithic catalyst that can be used for 2 and 4-stroke motorcycle applications. A new mounting technique was developed to contain the ceramic catalytic unit within a holder or converter shell with sufficient strength and durability to withstand the severe environment of 2-stroke engine exhaust.

Strategic Materials at Reaction Temperatures (SMART) is an approach used to design washcoat systems for passive 4-way emission control catalysts. Light duty diesel vehicles need to meet the European Motor Vehicle Emissions Group (MVEG) cycle or U. S. Federal test procedure (FTP 75). Emissions that are monitored include hydrocarbon (HC), nitrogen oxides (NOx), carbon monoxide (CO) and total particulate matter (TPM). Low engine-exhaust temperatures (< 200°C during city driving) and high temperatures (> 500-800°C under full load and wide-open throttle) make emission control a formidable task for the catalyst designer Gas phase HC, CO and NOx reactions must be balanced with the removal of the soluble organic fraction for the vehicle to be in compliance with regulations. The SMART approach uses model gases under typical operating conditions in the laboratory to better understand the function of individual washcoat components.

H2S emissions from a three-way catalyst are suppressed by incorporating copper or manganese oxide into a section downstream of the three-way catalyst.

On vehicles equipped with fuel shut-off, the rhodium in conventional TWC catalyst tends to strongly interact with the washcoat components during the high temperature lean excursions seen during deceleration. Studies were conducted to elucidate the conditions under which rhodium interacts with the alumina washcoat support and the rare earth components used in some of the new “High Tech” catalyst compositions. Technology was developed which decreased the rhodium interaction with these washcoat components which permits the catalyst to operate under a much broader set of engine control conditions. Laboratory hydrothermal and engine dynamometer aging studies were used to demonstrate the feasibility of lowering precious metal usage and especially rhodium content of TWC catalysts without sacrificing “High Tech” performance.

When the three-way conversion (TWC) catalysts were aged on representative 1977 unleaded commercial fuel, they had higher conversion efficiencies and improved durability than catalysts aged on modified 1975 FTP specification fuel containing approximately 0.025 g/gal Pb and low levels of phosphorus. As the rhodium content was increased in a series of platinum-rhodium TWC catalysts, the maximum conversion efficiency and durability increased, and the mine recovery ratio of Pt/Rh was found to be most susceptible to lead poisoning. However, good NOx efficiencies can be obtained from mine recovery ratio Pt/Rh TWC catalysts after 25,000 miles of engine aging. It is shown that improvements in catalyst formulations containing mine recovery ratio Pt/Rh resulted in higher conversion efficiencies. Monolithic TWC catalysts require approximately the same total precious metal as current oxidation catalysts.