Fundamentals
5-9
Oxygen (
O
2
)
The level of
O
2
in exhaust gas is an indicator of air-fuel ratio
leanness. The
O
2
is present in the air the engine inducts and mixes
with the
HC
for combustion. Since the atmosphere is about 21%
O
2
, the percentage of
O
2
in the exhaust gas after combustion
indicates air-fuel ratio leanness.
In
, the
O
2
concentration is at a steady low level when
the fuel mixture is richer than about 15:1, because all available
O
2
is consumed in the combustion process. As the mixture gets
leaner,
O
2
steadily increases, because less is used in combustion.
Higher concentrations of
O
2
in the exhaust are therefore directly
proportional to leaner air-fuel ratios.
Figure 5-7
: Oxygen Versus Air-Fuel Ratio
Summary of Contents for DGA 1000
Page 1: ...DGA 1000 Diagnostic Gas Analyzer...
Page 2: ......
Page 48: ...2 16 Analyzer Screen Display Features...
Page 68: ...3 20 Vehicle Testing...
Page 115: ......