Administrator
Data inscrierii: 23/Feb/2007
Mesaje: 149
|
Scz asa lam gasit si eu e in engleza dar pentru cei care vor sa faca ceva e interesant
-------------------------------------------------------------------------------------
The electrical control system consists of the ECU, along with the following sensors:
a) Throttle potentiometer - informs the ECU of the throttle position, and the rate of throttle opening/closing.
b) Coolant temperature sensor - informs the ECU of engine temperature.
c) Inlet air temperature sensor - informs the ECU of the temperature of the air passing through the throttle housing.
d) Lambda sensor - informs the ECU of the oxygen content of the exhaust gases (explained in PartD of this Chapter).
e) Crankshaft sensor - informs the ECU of crankshaft position and speed of rotation.
f) Manifold Absolute Pressure (MAP) sensor - informs the ECU of the load on the engine (expressed in terms
of inlet manifold vacuum).
g) Vehicle speed sensor - informs the ECU of the vehicle speed.
All the above signals are analysed by the ECU which selects the fuelling response appropriate to those values. The
ECU controls the fuel injectors (varying the pulse width – the length of time the injectors are held open – to provide
a richer or weaker mixture, as appropriate). The mixture is constantly varied by the ECU, to provide the best
setting for cranking, starting (with either a hot or cold engine), warm-up, idle, cruising and acceleration.
The ECU also has full control over the engine idle speed, via an auxiliary air valve which bypasses the throttle
valve. When the throttle valve is closed, the ECU controls the opening of the valve, which in turn regulates the
amount of air entering the manifold, and
so controls the idle speed.
The ECU also controls the exhaust and evaporative emission control systems, which are described in Part D of this
Chapter.
An electric heating element is fitted to the throttle housing; the heater is supplied with current by the ECU, and
warms the throttle housing on cold starts to prevent possible icing of the throttle valve.
If there is an abnormality in any of the readings obtained from either the coolant temperature sensor, the inlet air
temperature sensor or the lambda sensor, the ECU enters its back-up mode. In this event, it ignores the abnormal
sensor signal and assumes a preprogrammed value which will allow the engine to continue running (albeit at reduced
efficiency). If the ECU enters this back-up mode, the warning light on the instrument panel will come on, and the
relevant fault code will be stored in the ECU memory.
If the warning light comes on, the vehicle should be taken to a Peugeot dealer at the earliest opportunity. A
complete test of the engine management system can then be carried out, using a distinct electronic diagnostic test
unit which is simply plugged into the system’s diagnostic connector
The Magneti Marelli 8P engine management (fuel injection/ignition) system is very similar in operation to the
Bosch MP5.1 system described above, apart from the idle speed control system.
On the Magneti Marelli system, the idle speed is controlled by the ECU via a stepper motor fitted to the throttle
housing. The motor has a pushrod controlling the opening of an air passage which bypasses the throttle valve.
When the throttle valve is closed, the ECU controls the movement of the motor pushrod, which regulates the
amount of air which flows through the throttle housing passage, so controlling the idle speed. The bypass passage
is also used as an additional air supply during cold starting.
AVL Driveability Technology as On-Board Control System
The vehicle character adapts on-line to the driver. In the selection of the limits, of course, all legal and diagnosis regulations have to be considered.
In the modern torque-controlled engine management systems, a character adjustment can be carried out by many means. The basis is always the so-called accelerator pedal or torque demand map.
From the manufacturer’s point of view, considerable compromises are required to meet the requirements of various customer groups. Gentle drive-away and gear-changing behaviour are required by many customers, but usually conflict with spontaneous strong pedal response behaviour. Another typical contradiction is to be found in spontaneous response behaviour and jerking or surge.
The fuel supply system consists of a fuel tank (mounted under the rear of the car), with an electric fuel pump either mounted externally or internally in the tank, a fuel filter, fuel feed and return lines. The fuel pump supplies fuel to the fuel rail, which acts as a reservoir for the four fuel injectors which inject fuel into the inlet tracts. The fuel filter incorporated in the feed line from the pump to the fuel rail ensures that the fuel supplied to the injectors is clean. Refer to Section 6 for further information on the operation of each fuel injection system, and to Section 21 for information on the exhaust system. Throughout this Section, it is also occasionally necessary to identify
vehicles by their engine codes rather than by engine capacity alone. Refer to the relevant Part of Chapter 2 for further information on engine code identification.
The Bosch L3.1 fuel injection system is of the intermittent type operating under low pressure. Fuel is drawn from the rearmounted fuel tank by an externally-mounted fuel pump and delivered through an in-line filter to the injectors. A pressure regulator mounted on the outlet side of the fuel rail, and connected by pipe to the inlet manifold to sense vacuum, maintains a constant pressure at the injectors according to the depression in the inlet manifold, returning excess fuel to the fuel tank. A pulse damper on the inlet side of the fuel rail damps out the pressure pulses caused by
the operation of the injectors. The electronic control unit (ECU) and airflow meter are mounted on the air filter housing. The ECU uses signals from various sensors to determine the opening period of the injectors for any given engine operating condition. The inputs are as follows. Amount of air being drawn in by the engine via the airflow meter. Inlet air temperature via the thermistor mounted in the airflow meter. Engine speed and angular position via the injection (coolant) thermistor. Throttle position via the throttle switch unit. The injectors operate simultaneously, spraying fuel onto the inlet side of the inlet valves. A supplementary air device is fitted to the system to compensate for the extra fuel required during cold start conditions. The principle of operation of the LU2- Jetronic system is similar to that described for the L3.1-Jetronic system but with the following differences.
a) A single-barrel throttle body is fitted.
b) An oxygen sensor is fitted.
c) A catalytic converter is fitted.
The most significant difference is that the LU2-Jetronic system incorporates an oxygen sensor in the exhaust system, which enables
the electronic control unit to carry out fine fuel/air mixture adjustment to allow the use of a catalytic converter. The principle of operation of the Motronic MP3.1 system is similar to that described for the L3.1-Jetronic system but with the following differences.
a) The ECU controls the ignition system in
addition to the fuel injection system,
providing an integrated engine
management system.
b) A static (distributorless)ignition system is
used.
c) An inlet air temperature sensor and a
manifold absolute pressure (MAP) sensor
are used in place of the airflow meter.
d) An engine speed/position sensor is used
to provide information on engine speed
and crankshaft position.
Cam asta ar fi hai k mai vin eu cu ceva.... |
|
