939005757 - INTRODUCTION - PETROL FUEL INJECTION SYSTEM
SPECIFICATIONS
4 cylinder in line engine, sequential, phased type integrated injection and ignition system, 16 valves, dual overhead camshaft, continuous adjustment through phase transformer, motorized throttle body; equipped with Simtec 75.3 injection system and control unit produced by Siemens VDO.The unit is a system made up of the engine and all circuits required for its operation:- fuel supply system- air supply system- engine cooling system- exhaust system with catalytic converter built into the exhaust manifold- fuel vapour recirculation system.The operation of these systems is optimised by an electronic control system governed by a control unit.
Operation of the injection system - ignition
The Simtec 75.3 system with a motorized throttle manages the sequential, phased type electronic injection and ignition function.The control unit controls the air flow rate at the idling speed set by the electronic throttle.The control unit controls the ignition time, with the benefit of maintaining smooth engine operation even when environmental and applied load parameters and engine operating conditions change.The control unit controls and manages the injection so that the air/fuel ratio is always close to the stoichiometric ratio to ensure maximum conversion efficiency for the catalytic converter.The main system functions are essentially as follows:- self-learning;- system self-adaptation;- autodiagnosis on K line;- recognition of Alfa CODE (Immobilizer) on the CAN serial line;- cold starting control;- control of combustion - Lambda sensors;- check on phase transformers and modular intake manifold;- detonation control;- control of mixture enrichment during acceleration;- fuel cut-off during release of accelerator pedal;- fuel vapour recovery;- control of maximum rpm;- fuel pump control;- climate control system control;- cylinder position recognition;- control of optimum injection time for each cylinder;- adjustment of ignition advance;- idle speed management (also dependent on battery voltage - electrical balance management function);- management of throttle opening laws (accelerator pedal - torque request maps);- 3 speed fan control;- connection with ABS/ASR/VDC control unit;- cruise control (where fitted);- connection with the control panel;- torque management;- control of engine coolant temperature by means of electrically adjusted thermostatEOBD OPERATION:- fuel system diagnostics;- catalytic converter diagnostics;- misfire diagnosis; detection of failed combustion;- Lambda sensor diagnosis (pollution or signal distortion).Torque control strategyThe drive-by-wire control systems are vital in satisfying the legal requirements such as those regarding fuel consumption and emissions, as well as for improving the driveability of vehicles with petrol engines (starting, heating, dynamic transition response, safe driving).The torque for petrol engines is mainly affected by the throttle valve which controls the mass of air introduced by the engine, (depending on the position of the accelerator pedal; more precisely, the request for torque by the user, coming from the accelerator pedal, does not directly control the opening of the throttle valve, as in traditional systems with mechanical bowden cables, but is processed electronically by the control unit before being implemented by the throttle electric motor), and therefore also the filling of the cylinder.In addition to this there are other parameters that affect the variation of the engine torque: the ignition angle, the air/fuel (Lambda) ratio, the deactivation of injection for some cylinders.INJECTION SYSTEM
The essential conditions to be met by the air-fuel mixture for efficient operation of engines with controlled ignition systems are mainly as follows:- the metering (air/fuel ratio) must be kept as close as possible to the stoichiometric value to ensure maximum catalytic converter conversion capacity (max. efficiency).- the homogeneity of the mixture, consisting of petrol distributed throughout the air as finely and uniformly as possible.Information that the control unit processes to control optimum metering is received by electrical signals emitted by:- air flow meter (debimeter) and (built in) air temperature sensor, for the exact quantity of air taken in- rpm sensor, which produces the digital signals created by the variations in the magnetic field (Hall effect).The control unit uses this signal to detect MISFIRE.- throttle potentiometer, to recognize the accelerator request conditions (the dual throttle potentiometer is, in reality, a safety feature of the DbW system and has the main function of monitoring the effective position of the throttle valve controlled by the activating motor, in particular during the management of possible fault conditions and the implementation of recovery strategies).The torque request information by the driver is recognized by the control unit by means of the accelerator pedal dual potentiometer.- coolant temperature sensors located on the thermostat and the radiator outlet;- Lambda sensors to determine the oxygen content of the exhaust gases and, via the downstream sensor, to diagnose the efficiency of the catalytic converter.IGNITION SYSTEM
The ignition system is the static, inductive discharge type (i.e. without a high voltage distributor).The ignition system has a single coil for each spark plug with an integrated power stage.The advantages of this solution are:- lower electrical overload;- guaranteed constant discharge at each spark plug.The control unit contains a memory map with a set of optimum ignition advance values (for the cylinder in combustion phase) that the engine can adopt according to the required speed and engine load.The control unit corrects the advance value mainly on the basis of:- engine coolant temperature- intake air temperature- detonation.- throttle valve position.Information that the control unit processes to operate the single coils is received by electrical signals emitted by:- air flow meter (debimeter) with built in air temperature sensor, for the exact quantity of air taken in;- rpm sensor;- detonation sensor (on the rear part of the crankcase between cylinders 2 and 3) to recognise the cylinder with knock and thus correct the ignition advance;- throttle position potentiometer to recognise minimum, partial and full load conditions.- timing sensors.The control unit uses the rpm signal to recognize misfiring that could damage the catalytic converters.DIAGRAM SHOWING INFORMATION ENTERING/LEAVING THE CONTROL UNIT
SYSTEM OPERATING LOGICS
Self-learning
The control unit implements the self-learning logic in the following conditions:- removing-refitting or replacement of the injection control unit;- removing-refitting or replacing the integrated throttle casing; | The Simtec 75.3 ECU carries out the throttle body learning procedure automatically at the next key-on.The values stored by the control unit are maintained when the battery is disconnected. |
System self-adjustment
The control unit is equipped with a self-adjustment function that is designed to recognise the changes that take place in the engine due to the processes of bedding in and ageing over time of both the components and the engine itself.These changes are memorised in the form of modifications to the basic map and are designed to adapt the operation of the system to the gradual alterations in the engine and the components compared with when they were new.This self-adjustment function also makes it possible to compensate for the inevitable differences in any replacement components (owing to production tolerances).The control unit modifies the basic map in relation to engine specifications when new, on the basis of exhaust gas analysis.The self-adjustment parameters are not deleted if the battery is disconnected.Self-diagnosis
The control unit auto-diagnostic system checks that the system is working properly and signals any irregularities by means of an (MIL) warning light in the instrument panel with a standardised ideogram and colour, as stipulated by European regulations. This warning light indicates engine management faults and also faults detected by EOBD diagnostic strategies.The MIL warning light operating strategy is as follows:- with the ignition on, the warning light comes on and remains on until the engine has been started up. The control unit self-diagnostic system checks the signals coming from the sensors and compares them with the permitted limits.Fault indication during start up:- the failure of the warning light to go out when the engine has been started indicates that there is an error memorised in the control unit.Fault indication during operation:- the warning light comes on in flashing mode to indicate possible catalytic converter damage due to misfiring.- the warning light comes on in constant mode to indicate the presence of engine management or EOBD diagnostic errors. | Not all faults lead to the MIL EOBD warning light coming on. The effective presence of faults should be checked by reading the control unit errors memory with the diagnostic socket on the K line. |
Alfa code recognition
The moment the control unit receives the ignition ON signal it converses with the Alfa CODE control unit (via the body computer on the CAN serial line to obtain the go ahead for starting.)Cold starting control
The following occurs in cold starting conditions:- a natural weakening of the mixture as a result of poor evaporation of the fuel at low temperatures;- fuel condensation on inner walls of the intake manifold;- increased lubrication oil viscosity.The electronic control unit detects this condition and corrects the injection time on the basis of:- coolant temperature;- intake air temperature;- battery voltage;- engine rpm.The ignition advance is determined solely on the basis of rpm and coolant temperature.Whilst the engine is warming up, the control unit operates the motorized throttle to regulate the quantity of air required to ensure that the engine does not cut out.The rotation speed decreases proportionally as the engine temperature increases, until the nominal value is reached when the engine has warmed up.Control of combustion - lambda sensors
In EOBD systems, the Lambda sensors are all the same type and are located upstream of the catalytic conversion system and downstream of the converter. The upstream sensors monitor concentration and are known as the 1st loop (closed loop of upstream sensor). The sensor downsream of the catalytic converter is used for the fault diagnosis of the catalytic converter (in the Simtec 75.3 system the downstream sensor is only used to carry out the catalytic converter fault diagnosis).Control of the phase transformer and modular intake manifold
In order to ensure the optimum quantity of air introduced by the engine, the control unit controls:- continuous intake and exhaust timing;- the geometry of the intake manifolds in two lengths.At maximum torque the control unit controls the intake manifold in the the long duct position.At maximum power and idle the control unit controls the intake manifold in the short duct position.In all other engine operating conditions, the control unit selects the most suitable configuration for optimum performance, consumption and emissions.Control of detonation
The control unit detects the presence of detonation (engine knock) by processing the signal coming from the relevant sensor.The control unit continuously compares the signals coming from the sensor with a threshold which is, in turn, continually updated to take into account background noise and engine ageing.The control unit is therefore capable o| ... DATA ERROR - CROPPED TEXT | Ошибка данных - Текст обрезан ... |
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