125000242 - INTRODUCTION - ENGINE

CONSTRUCTION FEATURES

JTS (uniJet Thrust System) engine with 4 cylinders in line, 1997 cc, static ignition with one plug per cylinder, twin overhead camshaft, electro-hydraulic variable valve timing, hydraulic tappets, 4 valves per cylinder, fuel system with high-pressure pump for direct injection, air supply system with modular inlet manifold, with Bosch Motronic MED7.1.1 integrated injection/ignition.

GENERAL CHARACTERISTICS

The unit comprises the engine and all the systems required for its operation:

  • fuel system;
  • air supply system;
  • engine cooling system;
  • exhaust system;
  • fuel vapour recirculation system
The operation of these systems is optimized by an electronic control system governed by a control unit.An understanding of the operating logic of the control unit gives an overall picture of the entire GROUP 10 system.

Operation of the fuel injection-ignition

The Bosch Motronic MED7.1.1 system with a motorized throttle belongs to the category of integrated systems with:

  • ignition
  • sequential and phased electronic injection.
The control unit controls the air flow rate at the rotation speed set through the electronic throttle.The control unit controls the moment of ignition with the advantage of keeping the engine running smoothly as the ambient parameters and loads applied vary.The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

The main operating principles of the system are basically as follows:

  • self-learning;
  • system self-adaptation;
  • autodiagnosis;
  • recognition of the Alfa Romeo CODE (Immobilizer);
  • control of cold starting;
  • control of combustion - Lambda sensors;
  • control of variable valve timing and modular inlet manifold
  • control of knock;
  • control of mixture enrichment during acceleration;
  • fuel cut-off with the accelerator pedal released;
  • fuel vapour recovery;
  • control of the maximum rpm;
  • control of high-pressure fuel pump;
  • connection to the climate control system
  • recognition of cylinder position;
  • control of the optimum injection time for each cylinder;
  • adjustment of ignition advance values;
  • management of the idle speed (also according to the battery voltage);
  • control of the electric fans;
  • connection with ABS/ASR control unit;
  • throttle opening management - CITY (Selespeed version);
  • connection with the automatic transmission control unit (where fitted);
  • connection with the instrument panel;
  • fuel system diagnosis;
  • catalyzer diagnosis;
  • detection of misfire;
  • Lambda sensors diagnosis.
Fuel injection system

The essential conditions that must always be met in the preparation of the air-fuel mixture for the correct operation of controlled-ignition engines are mainly:

  • the ''metering'' (air/fuel ratio) should constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the maximum conversion capacity for the catalytic converter (max. efficiency).
  • the ''homogeneity'' of the mixture, consisting of petrol, diffused as finely and evenly as possible in the air.

The information processed by the control unit for controlling optimum metering is received in the form of electrical signals emitted by:

  • air flow meter and air temperature sensor, for the exact quantity of air drawn in;
  • rpm sensor which produces an alternating, single-phase signal whose frequency indicates the engine rpm;
  • accelerator pedal with throttle potentiometer, to recognize the driver conditions requested;
  • – coolant temperature sensor on the thermostat;
- Lambda probes for determining the oxygen content in the exhaust gases.Ignition systemThe ignition system is the static advance, inductive discharge type (i.e. with no H.T. distributor).

The system has a single coil for each plug (MONOCOIL), with integrated power stage; the advantages of this solution are:

  • less electrical overload;
  • guarantee of constant discharge at each spark plug.
The ignition coils only receive a twin operating signal (two ignitions), during idling, separated only by the time required for recharging the coil. In all other conditions, the coils receive one signal only (single ignition).Stored in the control unit, there is a map containing the entire set of optimum ignition advance values (for the cylinder at the power stroke) that the engine can adopt in relation to the rpm and required engine load.

The control unit corrects the advance values mainly in accordance with:

  • engine coolant temperature;
  • intake air temperature;
  • detonation.

The information the control unit processes in order to drive the single coils is received in the form of electrical signals emitted by:

  • air flow meter and air temperature sensor, for the exact quantity of air drawn in;
  • rpm sensor which produces an alternating, single-phase signal whose frequency indicates the engine rpm;
  • detonation sensors to recognize the cylinder where detonation is occurring and correct the ignition advance;
  • throttle potentiometer, to recognize the minimum, partial and full load conditions;
  • timing sensor.
The control unit uses the rpm signal to recognize any misfire which could damage the catalyzers.

OPERATING

Diagram of input/output info to/from control unit
1 - Electric fuel pump2 - Air conditioner compressor3 - Electric fan4 - Lambda sensors upstream of the catalytic converters5 - Quadrinary6 - Brake - clutch pedal switch7 - Timing sensor8 - Speedometer9 - Lambda sensors downstream of the catalytic converters10 - Coolant temperature sensor11 - Brake servo vacuum sensor12 - Knock sensor13 - Rpm sensor14 - Accelerator pedal with integrated potentiometer15 - Air flow meter with air temperature sensor16 - Battery17 - Throttle body integrated with D.V.L.18 - CAN line (for communication with ABS/ASR control units and automatic transmission)19 - Alfa Romeo CODE20 - Diagnostic socket21 - Fuel vapour recirculation solenoid22 - Ignition coils23 - Engine Check warning light24 - Rev counter25 - Injectors26 - Modular inlet manifold solenoid valve27 - Variable valve timing

System operating modes

Self-learning

The control unit implements the self-learning mode in the following conditions:

  • installation of new injection control unit,
  • installation of a new throttle body actuator integratd with D.V.L.
  • installation of a new modular intake manifold.
The learnt values of the throttle body integrated with D.V.L. are preserved if the battery is disconnected.The learnt values of the phonic wheel for recognizing misfire are instead lost.
System self-adaptationThe control unit has a self-adaption function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.There are two adaptation functions according to two intervention plans: minimum and usage.
Self-diagnosisThe control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram. This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

  • with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The control unit''s self-test checks the signals coming from the sensors, comparing them with the permitted limits:

Signalling of faults during engine starting:

  • the failure of the warning light to go out after the engine has been started up means that there is an error memorized in the control unit.

Fault indication during operation

  • the warning light flashing indicates possible damage to the catalytic converter due to misfire.
  • the warning light constantly on indicates the presence of engine management errors or EOBD errors.
RECOVERYFrom time to time, the control unit defines the type of recovery according to the components which are faulty. The recovery parameters are managed by those components which are not faulty.
Recognition of the alfa romeo codeWhen the control unit receives the ignition ''ON'' signal, it communicates with the Alfa Romeo CODE control unit to obtain starting enablement.
Control of cold starting

In cold starting conditions there is a natural weakening of the mixture which causes poor evaporation of the fuel at low temperatures:

  • condensation of the fuel on the inner walls of the inlet manifold;
  • increased viscosity of the lubricant oil.

The electronic control unit recognizes this condition and corrects the fuel injection time in accordance with:

  • coolant temperature;
  • intake air temperature;
  • battery voltage;
  • engine rpm.
The ignition advance depends solely on the engine rpm and the coolant temperature.During starting, the control unit controls a first simultaneous injection for all the injectors (full-group injection) and, after recognizing the timing of the cylinders, it starts normal sequential phased operation.During idling, the injection angle is 45° before T.D.C. (with a stratified charge); at other speeds, the injection angle varies between 310° ανδ 370° βεφορε Τ.D.C. to allow the homogeneity of the mixture.Whilst the engine is warming up, the control unit operates the throttle body integrated with D.V.L. to regulate the quantity of air required to ensure that the engine does not cut out.The rpm is made to decrease as the temperature of the engine increases until the optimum value with the engine warmed up is obtained.
Check on combustion - lambda probeIn EOBD systems the Lambda sensors, which are all the same type, are located upstream and downstream of the catalyzer.The upstream sensors carry out the check on the mixture strength known as the 1st loop (upstream sensor closed loop). During idling, the information from the upstream Lambda sensors is not used for correcting the mixture strength.The sensors downstream of the catalyzer are used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters.With this in mind, the adjustment of the second loop is designed to recover both production differences and those in the response of the upstream sensors which may occur as a result of ageing and pollution.This control is known as the 2nd loop (downstream sensor closed loop).
Check on variable valve timing and modular inlet manifold

To optimize the quantity of air drawn in by the engine, the control unit checks:

  • inlet timing at two angular positions;
  • geometry of inlet ducts over two lengths.

At the maximum torque speed, the control unit sets the open phase:

  • cam advanced by 25° engine;
  • modular inlet manifold long ducts

At the maximum power speed, the control unit sets the closed phase:

  • cam in normal position
  • modular inlet manifold short ducts.

During idling, the control unit sets the closed phase:

  • cam in normal position
  • modular inlet manifold short ducts.
In the other engine operating conditions, the control unit selects the most suitable configuration to optimize performance - consumption - emissions.During overrunning, the module inlet manifold inlet ducts are always short.
Check on knocking

The control unit can delay the ignition selectively at the cylinder required, according to the combination of figures received from the detonation and timing sensors and:

  • reduces the ignition advance in steps of 3° up to a maximum of 9°;
  • updates the level to take into account background noise and ageing of the engine
During acceleration, the control unit uses a higher threshold for the increased engine noise.When the detonation disappears, the control unit increases the ignition advance in steps of 0.75° υντιλ ιτ ισ χομπλετελψ ρεχοϖερεδ.

With the auto-adjustment function, the control unit:

  • memorizes the various advance reductions, continuously repeated;
  • adapts the map to the diff
... DATA ERROR - CROPPED TEXT | Ошибка данных - Текст обрезан ...