Three way Catalyst with faster light-off substrates – A promising approach to reduce tailpipe emissions

The ever-tightening regulation norms across the world emphasize the magnitude of the air pollution problem. The decision to leapfrog from BS4 to BS6 - with further reduction in emission limits - showed India's commitment to clean up its atmosphere. The overall cycle emissions were reduced significantly to meet BS6 targets. However, the introduction of RDE norms in BS6.2 demanded further reduction in emissions under real time operating conditions - start-stop, hard acceleration, and idling, cold start - which was possible only through strategies that demanded a cost effective yet robust solutions. The first few seconds of the engine operation after start contribute to major amount to the cycle gaseous emissions. This is because the thermal inertia of the catalytic converter restricts the rate at which temperature of the catalyst increases and achieves the desired "light-off" temperature. The challenge becomes more prominent in the turbocharged engines which puts additional heat 'loss' leading to lower catalyst in gas temperatures, specifically at ambient/cold starts. In order to achieve better emission performance, an innovative approach is needed to attain quicker catalyst "light-off" as any change in only noble material content may not yield the optimum solution. An innovative and efficient approach by combining key contributor's calibration strategies and base catalyst design - were used. Though in-cylinder based strategies to increase EGT exist, they impose an additional fuel penalty along with issues like oil dilution. A much better way - avoiding the issues above - to improve the EGT profile is to reduce the thermal inertia of the catalytic converter. This is the idea behind introducing high-porosity substrates. A new Corning© FLORA© substrate with a higher porosity (55%) compared to the standard substrates (35%) was adopted as a front substrate in a twin brink catalyst design. As Higher porosity reduces the thermal inertia of the substrate which in turn aids in rapid catalyst temperature rise and faster light-off. This new combination with FLORA© on 1.2 L MPFI REVOTRON engine, resulted in an improved the emissions performance even with a lower PGM content. A reduction of 10 to 30% in regulated pollutants with an approximately 10% lower noble material loading. The paper describes the innovative approaches taken in the design of the CCC, Calibrations methodology & new FLORA© substrate contributions. The work was carried on Tata Passenger vehicle with a 1.2L MPFI REVOTRON engine meeting BS6 Stage II emissions.