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Higher fuel costs and lower greenhouse gas standards, especially CO2, have compelled vehicle manufacturers to downsize engines while simultaneously using turbochargers on more of their applications. The application of turbochargers improves fuel economy as well as torque and power. However, this also results in lower exhaust temperatures which can challenge the ability of three-way catalysts to achieve low emission levels. This work investigates and compares the catalyst heat-up strategies, hardware, and catalyst architecture of four turbocharged 4-cylinder vehicles: a 2010 VW 2.0L DI, a 2013 Chevy Malibu 2.0L DI, a 2013 Ford Fusion 1.6L DI, and a 2013 Dodge Dart 1.4L Multi-Air. In addition, three emission studies are presented. One study will show a strategy to reduce PGM concentrations in a close-coupled (CC) catalyst.

Dual-monolith catalyst systems containing Pd/Rh three-way catalysts (TWCs) provide effective emission solutions for LEV2/Bin 5 and Bin 4 close-coupled applications at low PGM loadings. These systems combine washcoat technology and PGM distribution for front and rear catalysts resulting in optimal hydrocarbon and NOx light-off and transient NOx control. The dual-catalyst [Pd/Rh + Pd/Rh] systems are characterized as a function of Pd-Rh content, PGM location, and catalyst technology for 4-cyl [close-coupled + underfloor] systems and 6-cyl close-coupled applications. The current Pd/Rh dual-catalyst converters significantly reduce NOx emissions compared to earlier [Pd + Pt/Rh] or [Pd + Pd/Rh] LEV/ULEV systems by utilizing uniform Rh distribution and new OSC materials. These new design strategies particularly impact NOx performance, especially during transient A/F excursions.