Air Fuel Ratio (A/F) Sensor Construction/Operation; Heated Oxygen Sensor (Ho2S) Function [13B-Msp]; Heated Oxygen Sensor (Ho2S) Construction/Operation - Mazda RX-8 2009 Service Highlights

AIR FUEL RATIO (A/F) SENSOR CONSTRUCTION/OPERATION [13B-MSP]
Installed on the exhaust manifold.
The wide-range air/fuel ratio sensor is a pump cell
type sensor, using both the oxygen concentration
cell action and oxygen pump cell action, and can
detect the oxygen concentration (air/fuel ratio of
the air-fuel mixture) in the exhaust gas in all
ranges, from lean to rich.
A heater is built into the sensor to facilitate the
activation of the A/F sensor at engine startup
(when the exhaust gas temperature is low).
Operation
The wide-range air/fuel ratio sensor converts the
oxygen concentration in the exhaust gas into a
current value, and sends the value to the PCM.
The PCM calculates the
air-fuel mixture based on the received current
value.
( (lambda)) = (actual air/fuel ratio)/
(stoichiometric air/fuel ratio)
End Of Sie

HEATED OXYGEN SENSOR (HO2S) FUNCTION [13B-MSP]

Detects the oxygen concentration in the exhaust gas.
A heater has been adopted, allowing stable detection of the oxygen concentration even when the exhaust gas
temperature is low.
End Of Sie
HEATED OXYGEN SENSOR (HO2S) CONSTRUCTION/OPERATION [13B-MSP]
Installed on the catalytic converter.
A heater is built into the sensor to facilitate the
activation of the HO2S at engine startup (when
the exhaust gas temperature is low).
A zirconium element is used on the sensor. When
there is a difference between the oxygen
concentration inside and outside the element,
electromotive force is generated by the movement
of oxygen ions (inside of the zirconium element:
atmosphere, outside: exhaust gas). The
electromotive force changes significantly at the
boundary of the stoichiometric air/fuel ratio (A/
F=14.7). The PCM receives the voltage
generated from the HO2S directly, and increases
or decreases the fuel injection amount by the fuel
injection control so that it is close to the
stoichiometric air/fuel ratio.
01-40–26
2009 Mazda RX-8 Service Highlights (3452–1U–08C)
CONTROL SYSTEM [13B-MSP]
(lambda) value of the
A/F SENSOR
1
0.5
0
-0.5
-1
-1.5
1.1
1
0.7 0.9
0.8
14.7 16.17 17.64 19.11 20.58
13.23
10.29 11.76
id0140g1256100
ar8uun00000251
1.4 (λ)
1.2 1.3
(A/F)
ar8uun00000214
id0140g1173700
id0140g1173800
HO2S
ar8uun00000252