F. Full power

F. Full power

During engine operation at full load (with throttle fully open) baseline injection times are increased to enrich the air-fuel mixture. During this operating stage, the ECU also disenables the Lambda probe function.

G. Fuel cut-off during over-run (cut-off)

With throttle closed and rpm more than a threshold level (about 1200 rpm), the ECU deactivates fuel injection. In this way the number of revs drops quickly to a minimum and fuel is saved for a considerable improvement in fuel economy. The cut-off threshold varies according to engine temperature.

H. Idle speed control

Idle speed is adjusted by means of a special actuator that acts on the throttle by-pass.

This also acts as an additional air valve and regulator for the activation of various appliances (e.g. air conditioner compressor); with the throttle closed, the actuator adjusts the by-pass opening to make up the power required by the appliances in order to ensure idle speed is as constant as possible.

The actuator ensures prompt regulation because by-pass opening and closure are both controlled by magnetic coils.

The vehicle speed signal is also considered for the idle strategy; this establishes whether vehicle is idling at a standstill or moving.

NOTE The system self-adaptation funciton allows any idle speed adjustment to be eliminated. The ECU recognises the "throttle closed" position from the throttle case sensor. This allows it to monitor wear that may arise in the closed position.

I. Limitation of maximum rpm

The maximum rpm limitation management and control strategy is as follows:
the ECU cuts off injection at 6700/min.

L. Vehicle speed signal

In the M2.7 system, the vehicle speed signal allows the ECU to recognise when 1st gear is engaged. This is achieved by comparing engine rpm with vehicle speed. In this case the ECU's function is to limit turbo pressure in the case of sprint starts to prevent the drive wheels skidding excessively (antispin function.)

M. Connection to antitheft device

If an antitheft device is fitted and turned on, this automatically inhibits operation of the injection-ignition ECU (Motronic).

N. Control of detonation or knock

Knock (or detonation) is controlled by a sensor housed on the monobloc.

When the engine knocks, vibrations of a certain frequency are set up in the crankcase. The effect causes mechanical repercussions on a piezoelectric crystal in the sensor that sends a signal to the ECU. The ECU carries out selective recognition of detonation cylinder by cylinder via detonation sensor and uses the rpm and TDC sensor to detect the angular position of the crankshaft upon the next cycle, i.e. after two crankshaft rotations. Then upon the exhaust stage of the same cylinder, the ignition advance is reduced (the delay occurs 3° by 3° to a maximum of 12°).