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Fuel injection, basic function

Fuel injection, basic function


1. Basic calculation of fuel mass/combustion


The current air mass/combustion is divided by 14.7 and sent to box 2. The unit is now mg fuel/combustion.

2. Compensation

In the case of a cold engine, shortly after starting, rapid load changes, knocking or a high load, the current value is multiplied by a compensation factor.

3. Closed loop

The closed loop value is also used as a multiplier. The value is sent to box 4.

4. Correction for purging

Multiply by the value for purging adaptation. The value is sent to box 5.

5. Multiplicative adaptation

The multiplicative adaptation value is also used as a multiplier and the new value sent to box 6.

6. Additive adaptation

The additive adaptation value is added and the new value sent to box 7.

7. Fuel mass, secondary air injection


More fuel is added if SAI is active.

8. Engagement of SAI fuel

9. Addition of SAI fuel

10. Starting fuel mass

Starting fuel mass is selected if the engine has not been started.

11. Fuel mass/combustion


Fuel mass/combustion is the fuel mass to be supplied to the engine for each combustion.

12. Injector opening duration

Converts fuel mass to nozzle opening duration in ms.

13. Injection twice/combustion

Before the engine has been synchronised, i.e. the camshaft position has been detected by the ignition system, fuel will be injected twice per combustion. The injection duration calculated in block 12 is divided by two.

14. Needle lift compensation

Voltage dependent needle lift duration is added to the injection duration. This compensates for the delay between the current in the injector coil being activated and the fuel arriving.

15. Fuel shut-off

Fuel shut-off can come into question under certain conditions, e.g. when engine braking, car immobilized. Injection duration is then zero.

16. Selection of fuel shut-off function

17. Activation of injector

ECM controls the injector that is about to deliver fuel, the sequence depends on the firing order. The crankshaft angle during which injection takes place depends on the prevailing operating conditions.