Page 45 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Introduction 27

The starting point for legislation for monitoring catalytic converters was in 1988 in the United
States, with the OBD I1 (On-Board Diagnostics) standard. The definite form of this standard
was issued in I99 1 by the California Air Resources Board (CARI3) and was introduced in
California in 1994. Further extensions of this legislation have been proposed in the United
States by the Environmental Protection Agency (EPA), and also in Europe, under the common
name of EOBD (European On-Board Diagnostics) (see EP0588123 (1994)).
The OBD 11 specifications include installation in motor vehicles of electronic systems which
can monitor periodically the efficiency of anti-pollution devices, or in general, can detect and
indicate the occurrence of phenomena liable to produce an excessive increase in emissions by
the vehicle.
Table 4 summarizes all emission reduction measures that are monitored by a modem OBD
system ([2]).

Legislation HC (gkm) CO (gkm) NOx khm)
EPA 0.12* 1.06* 0.31*
1.5 x the respective 1.5 x the respective 1.5 x the respective
CARB (TLEV) emission limits emission limits emission limits
I .5 x the respective 1.5 x the respective 1.5 x the respective
CARR (LE kj emission limits emission limits emission limits
1.5 x the respective I .5 x the respective 1.5 x the respective
CARR (ULEV) emission limits emission limits emission limits
European 0.4 3.2 0.6

Table 5: Malfhctioning criteria for catalytic converters

The main anti-pollution device, which requires monitoring in order to indicate malhnctioning
in terms of exceeding some predefined threshold values for emissions measured in the type-
approval test cycle (for example the so-called FTP '75 cycle), is the catalytic converter
installed in the exhaust pipe (see EP0588123 (1994)).
Tables 5 and 6 show the malfunctioning criteria for catalytic converters for different emission
technology vehicles for EPA, CARB and European legislation. The case of Transitional Low
Emission Vehicles (TLEV) is also included. ([9], [IS] and [16]).