• Video
  • 30-Jan-2012 12:18 EST

Evaluation of a NOx Transient Response Method for OBD of SCR Catalysts


Purchase Required to View Video

Short Preview Below

OBD requirements for aftertreatment system components require monitoring of the individual system components. One such component can be an NH3-SCR catalyst for NOx reduction. An OBD method that has been suggested is to generate positive or negative spikes in the inlet NH3 concentration, and monitor the outlet NOx transient response. A slow response indicates that the catalyst is maintaining its NH3 storage capacity, and therefore it is probably not degraded. A fast response indicates the catalyst has lost NH3 storage capacity, and may be degraded. The purpose of the work performed at Southwest Research Institute was to assess this approach for feasibility, effectiveness and practicality. The presentation will describe the work performed, results obtained, and implications for applying this method in test laboratory and real-world situations.

Gordon J. Bartley, Southwest Research Institute

Purchase to View
HTML for Linking to Page
Page URL
Rate It
5.0 Avg. Rating
1 votes

View More Video

The introduction of hybrid and plug-in hybrid electric vehicles has resulted in the introduction of battery systems into the realm of OBD II diagnostics. After a high-level overview of battery systems, general battery system fault responses are discussed, as well as which of these might be OBD faults. The alignment of the OBD regulations and DTC assignment in systems with large numbers of similar/identical components is discussed, along with apparent conflicts between existing OBD regulations and the physical realities of battery systems in HEVs and PHEVs. Presenter Dyche Anderson, Ford Motor Co.
Update on heavy-duty regulations. Presenter Michael J. McCarthy, California Air Resources Board
While providing significant benefits to vehicle operation and emissions, on board diagnosis comes at a cost. In many cases the additional cost comes in the form of reduced optimal performance. Often the additional cost can be mitigated by considering the OBD requirements early in the development stages. In this presentation we show these trade-offs in a number of case studies. We will point out where the ability to diagnose comes at the cost of suboptimal performance, and where system design decisions can facilate the OBD task. Presenter Michiel Van Nieuwstadt, Ford Motor Co.
Plug-in Hybrid Electric Vehicles (PHEVs) are entering the market and bring with them new OBD issues. A key one is how to measure in-use monitor performance ratio and where to set a standard for this, as PHEVs will have varying amounts of engine-on operation depending on customer plug-in and driving behavior. Toyota�s Prius PHEV system is described and customer use data from a US demonstration fleet is examined. Some prior denominator proposals by Toyota and CARB are explained, as background for the current CARB/industry agreement for denominator and ratio. Presenter Morton M. Smith, Toyota

Related Items

Technical Paper / Journal Article