A Case Study in DOC OBD Limit Parts’ Performance and Detection 2021-01-0438

The reduction of automotive emissions is instrumental in the fight against air pollution and its impact on global warming. This realization has empowered governments around the world to mandate lower levels of vehicle emissions requiring the Original Equipment Manufacturers (OEMs) to implement advanced aftertreatment technologies in their applications. Achieving emission levels as low as SULEV30 or SULEV20 would have been impossible only a couple of decades ago, however, these lower levels of emissions are now a possibility through advanced control strategies and aftertreatment systems. As a part of this mandate to lower emissions, OEMs are also continuously monitoring the health and performance of their aftertreatment and control components. The implementation of On Board Diagnostics (OBD) ensures that control systems are functioning robustly and the emission levels are achieved and maintained to high mileages for the life of the vehicle. To develop a robust OBD detection strategy, OEMs often create limit or threshold parts that mimic the failed part at the OBD detection limits. There are various methods for creating a limit part that would emit pollutant at the OBD limits.

In an effort to study different approaches to Diesel Oxidation Catalyst (DOC) limit part fabrication and their corresponding performance and detection, various DOCs were created each representing a unique failure mechanism. The emissions were measured and the impact of the damage on the emissions performance and OBD detection was investigated. From this, it was determined that only the limit DOCs which were created by cutting (volume reduction) and aging, have sufficient separation between their failed state and their acceptable emission performance, to be adequate for OBD activity during development.