M1.7 IGNITION AND INJECTION SYSTEM

The Motronic M1.7 (BOSCH) system is atechnologically modern system which manages the injection and ignition of 164 vehicle engines.

A control unit governs and adjusts all the engine parameters, optimizing performance and consumption by responding in real time to the differing running conditions. This new system mainly differs from its predecessors for its use of a "static distribution" type electronic ignition (with semi- conductors rather than distributor). This solution definitely brings with it advantages, as it eliminates moving parts subjected to wear, reduces noise levels and completely eliminates sparks, which consequently reduces the risk of interference: high voltage cables and connections are also reduced.

Another characteristic of this system is its "self-adaptation", ie. its ability to identify the changes taking place in the engine and compensate for them, in accordance with adaptive functions which correct the fuel plans and air flow programmed in the control unit.

There are two adaptive functions in particular for the fuel plan which operate in relation to the state of the evaporative solenoid valve (open or closed) plus an adaptive plan at idle speed; the latter is able to efficiently compensate for any air infiltrations. The continuous self-adaptation of the fuel plan allows the correct quantity of fuel to be maintained whatever the temperature and height.

NOTE: It is consequently necessary, after every intervention, to drive the vehicle for at least 10 minutes within the various running conditions, in order to signal to the control unit any changes which have taken place in the system and allow it to adapt to them.

SYSTEM FUNCTIONS

The system's main functions are the following:

The diagram which follows demonstrates the functions described. 

1.    LAMBDA PROBE                                      15.  THROTTLE POTENTIOMETER
2.    TACHOMETER                                        16.  INTAKE AIR TEMPERATURE SENSOR
3.    SPEEDOMETER                                       17.  THROTTLE BODY
4.    AIR FILTER                                        18.  CONSTANT IDLE SPEED ACTUATOR
5.    CONNECTION WITH ELECTRONIC AUTOMATIC TRANS-       19.  OIL VAPOR SEPARATOR
      MISSION                                           20.  PULSATION DAMPER
6.    HEATERNENTILATION UNIT CONNECTION                 21.  R.P.M. AND TIMING SENSOR
7.    SOCKET FOR SYSTEM DIAGNOSIS (FIAT TESTER)         22.  SPARK PLUG
8.    IGNITION/INJECTION CONTROL UNIT                   23.  IGNITION COIL
9.    POWER MODULE                                      24.  ELECTROINJECTORS
10.   KNOCK SENSOR                                      25.  EVAPORATIVE SOLENOID VALVE
11.   THERMOSTAT WITH COOLANT TEMPERATURE SENSOR        26.  FUEL FILTER
      (NTC)                                             27.  FUEL ELECTROPUMP
12.   CAM ANGLE SENSOR                                  28.  FUEL TANK
13.   FUEL PRESSURE REGULATOR                           29.  RELAY ASSEMBLY
14.   AIR FLOW METER

Functional diagram of ignition and injection system 23

Regulation of injection times

Digital technology has made it possible to optimize consumption and performance using programmed maps, memorized within the electronic control unit, in relation to r.p.m. and engine Ioad.The control unit, with the help of the sensors which detect the many variants in play, controls the electroinjectors with extreme precision and speed. The injection time is mainly corrected on the basis of the battery voltage and the engine temperature.

Regulation of the ignition advance

Thanks to a mapping memorized within the control unit, the latter is able to calculate the advance in relation to engine load, the temperature of the intaken air and the engine. Once this information has been processed, the control unit delays ignition selectively on the cylinder which requires it through the combination of the values recorded by the knocking and cam angle sensors.

Control of cold starting

During cold starting, the system controls the ignition advance and injection time. The ignition advance depends exclusively from r.p.m. and the engine temperature; its value reaches a maximum with the temperature at -6oC (21 o F). The injection time is obtained from a value programmed in the control unit and corrected by measuring the intake air temperature, the engine temperature, the battery voltage and r.p.m. During the start-up stage, the control unit also controls the injection at each ignition impulse. When a certain r.p.m. is reached (in relation to engine temperature) the control unit returns the system to normal operating ie. injection control for each revolution of the crankshaft.

Control of enrichment during acceleration

During acceleration, if the variation in the signal from the air flow meter exceeds a predetermined value, the control unit adapts the injection to this new request as well as increasing it further in order that it rapidly reaches the r.p.m. requested. As it approaches the set r.p.m., the injection increase is progressively eliminated.

NOTE: the request for acceleration is also detected by the potentiometer located on the throttle; this allows optimal running conditions to be ensured, should the air flow meter fail, until an assistance point is reached.

Fuel cut-off during deceleration

The fuel cut-off during deceleration is of the adapted type. When the throttle is closed and the r.p.m. exceeds 1,700 (for engine speeds lower than 1,700 r.p.m., the cut-off function is not operative in order that an optimal drive-ability can be maintained) the injection of fuel is disactivated. If the supply is interrupted, the r.p.m. will start to fall more or less quickly in relation to vehicle conditions. Before reaching idle speed, the dynamics of the fall in r.p.m. is checked. If this exceeds a certain value, the fuel supply system is partially reactivated on the basis of a logic which envisages the "soft accompaniment" of the engine at idle speed. When this condition has been reached, the normal functions at idle speed are reactivated and cut-out during deceleration will only be reactivated if the fuel cut-off threshold is exceeded to prevent the engine from jerking. The reactivation thresholds for the fuel supply and cut-off vary in relation to engine temperature. Another fuel cut-off logic has been developed within the control unit which intervenes during partial deceleration, ie. when a lower engine load is requested. The function is only activated if the new conditions last for a set period of time and after the ignition angle has been adapted to the new situation.

Constant idle speed control

The regulation of the idle speed is driven, in all operating conditions, by the constant idle speed actuator which acts on the by-pass of the throttle. As well as controlling idle speed, it also acts as an additional air chamber and regulator for the operation of the various accessories (eg. heater/ventilation compressor); with the throttle valve at the stop limit, the actuator regulates the by-pass compensating for the power requested by the accessories in order to guarantee an idle speed which is, as far as possible, constant around 700 r.p.m. The actuator used in this version guarantees high speed regulation as both the opening and closing of the by-pass are controlled by magnetic coils. The correction of idle speed is carried out by regulating the advance as well as by the idle speed actuator as it takes effect quicker.

Limitation of max. r.p.m.

Once vehicles equipped with a manual gearbox have exceeded the threshold of 7,100 r.p.m. (6,500 r.p.m. for vehicles equipped with the electronic automatic gearbox) the injection of fuel is interrupted, which prevents the engine from overloading and to protect it when the r.p.m. is excessively high. For versions fitted with the electronic automatic gearbox, there is a particular function which limits the r.p.m. if the gear lever should accidentally be inserted in the "D" (drive) position when the r.p.m. is very high, in order to avoid damaging the gearbox.

Fuel control - lambda probe

The lambda probe informs the control unit of the state of the combustion of the AIR-FUEL mixture (LEAN MIXTURE and RICH MIXTURE). To obtain an optimal mixture, the quantity of airdrawn in by the engine should be equal to the theoretical value which is necessary to burn all the fuel which is injected. This means that the lambda coefficient (L, ) is equal to 1: 
             QUANTITY OF INTAKEN AIR
            --------------------------------------

             THEORETICAL QUANTITY OF AIR
             REQUIRED TO BURN ALL THE FUEL
             INJECTED


Therefore:

   L = 1     IDEAL MIXTURE

   L < 1     RICH MIXTURE

   L > 1     LEAN MIXTURE
The lambda probe, in contact with the exhaust gases, generates an electrical signal, the voltage value of which depends on the oxygen concentration present in the gases themselves. This voltage is characterized by a sudden variation when the composition of the mixture moves away from L =1. When the probe provides a low level of voltage (lower than 200 mV) the control unit recognises that the mixture is lean ( L > 1 ) and slightly increases the quantity of fuel injected. When the probe provides a high level of voltage (greater than 800 mV) the control unit recognises that the mixture is rich ( , < 1 ) and decreases the quantity of fuel injected.

The lambda probe varies the injection time so that the measurements oscillate between these two voltage values, so the engine normally works with a lambda coefficient between 0.986 and 1.006, values very close to the theoretical value of 1. 25

Fuel vapor recovery

The vapors in the fuel (which cause pollution according to the regulations) are collected in a vapor-liquid separator (canister) where they are condensed and from here they return in a liquid state to the tank through the pipes. The remaining vapors which come out of the separator are senttowards the engine where they are burned; this takes place through a solenoid valve which is controlled by a control unit in accordance with a precise logic. After the solenoid valve has been closed for 60 seconds, it opens to a certain gradient for 90 seconds. At the same time, the lambda probe measures the fuel and if there are no variations with respect to the base map, the control unit closes the solenoid valve. If a variation is recorded in the carburation, ie. if it becomes necessary to "wash" the canister, the control unit will extend the time for which the solenoid valve remains open by a further 90 seconds. Nominally the canister washing flow (solenoid valve opening) is 1 % of the air flow measured by the air flow meter; this is in order to have the most balanced adaptive plan in order to obtain a constant washing percentage with respect to the quantity of air measured by the air flow meter; this is to avoid disturbing the drive ability as much as possible.

Connection with the heater/ventilation system

When the heater/ventilation system is activated, the compressor absorbs the power from the engine which, at idle speed, may cut- out. To avoid this problem, the control unit adapts the air flow to the new request for power, by controlling the relative actuator (adaptation also takes place during use to maintain an optimal "drive ability"). The system has another function which is to interrupt the supply to the compressor for 5-10 seconds if the engine requests a high degree of power (quick acceleration).

Connection with the electronic automatic gearbox

The injection/ignition system sends the following information to the contol unit which controls the electronic automatic gearbox:

The injection/ignition system receives an engine torque reduction signal from the electronic automatic gearbox control unit each time the ratio changes, in order to facilitate and reduce the gear engaging times.