Page 21 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

4 Methods for Monitoring and Diagnosing the Efficiency of Catalytic Converters

diagnostic (OBD) systems that indicate when emissions are not conforming to standard and
require hrther investigation ([SI).

Fig. 2 shows the so called New European Driving Cycle (NEDC) adopted in 1989, that is used
in the European Union at the present and corresponds to the USA FTP '75 driving cycle of fig.
1 [34]. It has been applied since the beginning of 1993 to all passenger cars weighing less than
2500 kg. The driving cycle consists of two parts, a city driving part and an Extra Urban
Driving Cycle (EUDC) part. The EUDC part uses car speeds up to 120 km/h. The city driving
part consists of an extremely high idling time part (31%) and engine breaking and the mean
driving speed is only 19 km/h. In this way the NEDC does not filfil the aspect of a
representative city driving and as it can be seen in fig. 3 it covers only a small part of a real
engine operation field. This simply means that the emissions quantity allowed in this operation
range of an internal combustion engine is limited by the law. The comparison of the FTP '75
and the NEDC cycles shows that the FTP '75 cycle comprises a higher collection of load and
speed ranges when driving in the city than the corresponding European cycle (fig. 3).

B -start of I-

end of
end of
W
cycle
cycle
2 40 7
7
a2
B
0 195 ' 195 ' 195 ' 400
time (s)
time (s)
test duration : 1220 s
test length : 11,007 km
average cycle speed : 32.5 km/h
max. speed : 120km/h

Fig. 2 (from [34], p. 161)

Table 1 shows the European exhaust emission standards (restrictions) for passenger cars for
the four main pollutants Le. carbon monoxide (CO), nitrogen oxides (NO,), hydrocarbons
(HC) and particles. The EC96 (EURO TI) is the current European standard (effective January
1997), whereas the EC2000 (EURO 111) and EC2005 (EURO IV) correspond to the proposed