Injection Control

OPERATION
Injection Control
The Digital Motor Electronic (DME) control unit calculates the correct injection time on the basis of the engine speed, air flow, throttle position, oxygen sensor voltage. engine temperature and intake air temperature. The mixture is varied by the opening time of the injector valves. The battery or system voltage is also taken into consideration in calculating the injection timing since the pull-up and drop-out times of the injector valves are extended as the voltage decreases.

Types of Injection
Each injector valve group is driven by one output stage (power amplifier). This arrangement makes it possible to divide the injection cycle into cylinder groups (semisequential injection). This also facilitates restricted engine operation in the case of failure of one group.

Arrangement of injector valve groups:
6-cylinder: Cylinders 1+3+5 and cylinders 2+4+6

Semisequential Injection
As of an engine speed of 600 rpm, fuel is injected only once per 720 crankshaft angle into one cylinder group. This facilitates precise metering of the quantity of fuel since the injector valves need not be activated so often. It also enables restricted engine operation in the event of failure of one group.

Semisequential injection is only active when the DME control unit has received a signal from the cylinder reference point pulse generator. If this signal is not received during engine operation, the control system remains set to semisequential injection.

The cylinder reference point sensor is mounted on the ignition lead of cylinder No. 6 at the distributor.

Parallel Injection
Parallel injection refers to simultaneous activation of all injector valves and takes place only when the cylinder reference point sensor has supplied no signal since starting the engine. As soon as a signal is applied, the system switches over to semisequential injection after the next deceleration phase.