Lambda Sensor (B.258.040.092) - Fiat Bravo Service Manual

Engine
Fuel system
10.
2 3
1. Connecting cable
2. Protective sleeve
3. Planar sensor element
4. Ceramic support pipe
5. Sensor housing
6. Ceramic seal
7. Protective pipe
a. Rich mixture (lack of air)
b. Lean mixture (excess air)
30
4
L A M B D A S E N S O R (B.258.040.092)
The Lambda sensor is the "planar" type and is
fitted on the front section of exhaust pipe and
informs the injection control unit of the
progress of the combustion (stoichiometric
ratio).
To obtain an optimum mixture the quantity of
air drawn in by the engine must equal the
theoretical quantity for burning all the fuel in-
jected.
In this case the Lambda factor (X) i.e. the ra-
tio between the quantity of air drawn in and
the theoretical quantity of air (required to
burn all the fuel injected) is equal to 1.
Therefore:
X = 1 ideal mixture
X > 1 lean mixture
X < 1 richmixture
The Lambda sensor, in contact w i t h the ex-
haust gases, produces an electrical signal,
whose voltage value depends on the concen-
tration of oxygen present in the actual gases.
This voltage is characterized by a sharp varia-
tion w h e n the composition of the mixture
moves away from the value X = 1.
The heating of the Lambda sensor is man-
aged by the injection control unit proportion-
ality to the temperature of the exhaust gases.
This prevents thermal shocks to the ceramic
casing due t o contact w i t h the condensation
water, present in the exhaust gases, w i t h the
engine cold.
The measuring cell and the heater are incor-
porated in the "planar" (stratified) ceramic
element w i t h the advantage of heating the
cell rapidly to allow a closed loop control
(=1) w i t h i n a few seconds of the engine be-
ing started up.
Wiring connector
The numbers indicate the
control unit pins.
Bravo I 0 i 20v
98 range
corresponding
Print no. 506.670/16