ENGINE 1.3L QUADRAJET (90PS)
106
D. BOOST PRESSURE AND AIR TEMPERATURE
SENSOR
(i) Operational description
The sensor supplies a voltage proportional to the
measured pressure and is of piezo-resistive type
(resistance varies with pressure).
The ECU uses this information to determine:
Q
The mass of air absorbed by the engine (with the
engine speed and air temperature parameters),
Q
The flow to be injected at the various engine load
states and at the various atmospheric pressures,
Q
The ignition advance.
An altitude correction is also made to the injection
time calculation.
The mass of air absorbed by the engine effectively
varies as a function of:
Q
Atmospheric pressure, and therefore altitude,
Q
Air temperature,
Q
Engine speed.
Pressure measurements are taken:
Q
Every time the ignition is switched on,
At very high loads and low engine speeds (when
driving up a hill, and therefore change in altitude and
pressure).
(ii) Boost air temperature information
The resistance of the inlet air temperature sensor is
of NTC type (Negative Temperature Coefficient), and
therefore its resistance decreases as temperature
increases.
The ECU uses this information to calculate the mass
of air absorbed by the engine.
(iii) Fitment and location
It is fitted on the air intake manifold and the signal
sent to the engine management control unit makes it
possible to:
Q
Regulate the turbocharger pressure;
Q
Protect the engine against overheating;
Q
Diagnose the operation of the air flow meter.
(iv) Connection details and pin outs
Pin Description
Signal type
1 Earth
Earth
2 Air temperature sensor Analogue output
output
3 Power supply
+5 V input
4 Pressure sensor output Analogue output
The Turbo pressure & temperature sensor measures
the pressure and the temperature in the intake
chamber, downstream of the turbocharger. It is
supplied by pin 23 of Connector M of ECU and
receives a reference earth from pin 24 of Connector
M. Asignal corresponding to the pressure level is sent
to pin 41 of Connector M of ECU, the signal
corresponding to the temperature is sent to pin 37 of
Connector M.
