Integrated electronically controlled ignition and injection piloted by just one control unit ensure optimal i.c. engine performance and output, thus reducing consumption and harmful substances into the exhaust gas. These systems ensure accurate air-fuel ratio and optimal ignition advance.

The air-fuel mixture is given by the ratio, in weight, of air and fuel taken in by the engine: the ideal or stoichiometric ratio is that which establishes complete combustion. Excessive air or insufficient air give rise to, respectively, a lean (or weak) mixture or a rich mixture, which affect power and consumption, as well as emissions of exhaust gases.

Electronic control of the advance makes it possible to optimise the performance of the engine, the maximum power and the consumption and concentration of exhaust pollutants.

Electronic control for the ignition advance and fuel supply allows for optimal functioning of the engine under all conditions of use (low temperature start, warm-up stage, temporary acceleration / deceleration stages, engine under partial load, full load, idle).

The Marelli injection-ignition system is the Alfa/N type, in which the engine speed and throttle position are used as main parameters for measuring the quantity of intake air. If the quantity of air is known, the quantity of fuel is dosed in accordance with the required mixture. Other sensors in the system (engine sensor, atmospheric pressure, air temperature, engine oil temperature sensors and lambda sensor for CO control) are used to adjust the basic engine control strategy according to operating conditions. The engine speed and the throttle angle also make it possible to calculate the optimal advance for all types of operating conditions. The quantity of air taken in by each cylinder, during each cycle, depends on the density of the air in the intake manifold, the cylinder capacity and the volumetric efficiency.

Volumetric efficiency is experimentally taken onto the engine in the whole operating range (rotation speed and engine load conditions). Taken values are then used for the generation of a map which is stored into the I.A.W. 5 AM2 ECU Flash Eprom for injection control. The Flash Eprom can be programmed via serial line. Injectors are controlled through a "timed sequence", i.e. not at the same time. Fuel delivery to each cylinder can be started from the expansion stage up to the intake stage, already in progress. Delivery stop, that is when injectors are closed, is saved onto a special map, which is stored in the ECU Flash Eprom. Ignition is of the static inductive discharge type, featuring "dwell time" control so to ensure coil charging at steady power. Power modules for coil power supply are included in the CPU hardware. Advance curves are stored into the CPU Flash Eprom. Both coils and power modules are controlled by the ECU, which processes ignition advance.

For testing the components and relative wiring of the injection-ignition system, use the "DDS", following the indications under "Guided diagnosis" (Sect. D 5).

A pump located on a flange at the bottom of fuel tank pumps fuel into delivery tube (OUT) and toward injectors. The flange also fits the pressure regulator controlling fuel feed and keeping it constant at a value higher than engine-generated vacuum. Fuel which is not injected into intake manifolds goes back to the flange and then to the tank by means of a return tube (IN).

The engine control system (ignition and injection) relies on several sensors which correct mixture strength according to air pressure and temperature and engine load. An absolute air pressure and temperature sensor (4) -onto headlight support RH side- takes atmospheric pressure values and sends them to the ECU for necessary correction of injected fuel if riding on variable sea-level roads. It also allows the ECU to correct mixture strength according to air density. (Assuming that air volume is unchanging, if temperature is higher oxygen content will decrease, whereas it will increase if temperature is lower.

A throttle position sensor (6) is fitted onto the rear cylinder throttle shaft. It sends to ECU an indirect signal of air amount taken in by the engine (indirect value for engine load).

When the engine is fully warm, the unit calculates injection time and advance, by comparing the stored map values, in accordance with the RPM and throttle position. The calculated quantity of fuel is fed through injectors in one single sequential delivery to the two cylinders.

When the ignition switch is turned to ON, the control unit feeds the fuel pump for a few moments to put fuel feed hydraulic circuit under pressure. It receives the throttle position and engine temperature signals. When the engine is started, the unit receives the engine RPM and timing signals that allow it to proceed with injection and ignition. To facilitate start-up, the basic mixture is made richer in accordance with the engine temperature. During starting, the ignition advance is fixed (0°) until the engine starts. When the engine starts, the control unit takes over the advance control according to the values stored in the mapping and makes necessary corrections according to the air and engine temperatures.

During acceleration, the ECU makes the mixture richer for improved engine performance. Acknowledgement of this condition is given as the rider quickly turns the twistgrip to open the throttle. During a rapid deceleration, which is acknowledged as the rider quickly turns the twistgrip to close the throttle, the ECU makes the mixture leaner for reduced emissions and fuel consumption.