Snap-On Diagnostics DGA 1000, Руководство пользователя

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5-14
Fundamentals
Figure 5-12 shows NO
x
versus air fuel ratio after being treated by
a three-way catalytic converter. NO
x
levels are typically low when
the air-fuel ratio is more rich than stoichiometric. When the air-fuel
ratio is near stoichiometric and more lean than stoichiometric,
NO
x
levels increase, then fall to slightly lower values as the air-fuel
mixture continues to get leaner.
Catalytic converters oxidize
HC
,
CO
and
NO
x
producing
H
2
O
,
CO
2
and
N
2
. Therefore, monitoring
HC
and
CO
does not give an
accurate picture of engine performance because the catalytic
converter alters these gases. Using the analyzer to monitor
O
2
,
CO
2
,
HC
,
CO
and
NO
x
provides a more accurate method of
monitoring engine operation on vehicles with a catalytic converter.
Figure 5-12 :
NO
X
Vs. Air Fuel Ratio After Three-Way Converter Treatment