Injection

Fuel Injector
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Fully sequential fuel injection

In the fully sequential fuel injection system, each fuel injector is activated by its own output stage.
Fully sequential fuel injection offers the following advantages:
- Improved mixture preparation for each individual cylinder
- Adaptation of the injection timing to the relevant engine operating status (engine speed, load, temperature)
- Cylinder-selective injection correction under changing engine load conditions, i.e. during one operating cycle can vary the injection timing by means of post-injection, extending or shortening injection
- Cylinder-selective cutout is possible (e.g. in the event of defective cylinder coil)
- Diagnosis of each individual fuel injector is possible
These advantages of fully sequential fuel injection are gained because all cylinders are independently supplied with fuel.
Activation of each individual fuel injector by means of a separate output stage ensures that the presupply of the fuel is the same for all cylinders thus ensuring uniform mixture preparation quality for all cylinders. The presupply time is variable and is dependent on the engine load, speed and temperature.
In view of the fact that fuel injection only takes place once for each revolution of the camshaft the scatter of the fuel supply rate is low due to the component tolerances. Added to this, the idle quality is also improved as the energization and de-energization times at the fuel injectors are reduced. Fuel consumption is also slightly lower.
The injection timing can be corrected while driving as the result of sudden acceleration or deceleration. If the fuel injectors are still open, the mixture can be corrected at the valves that not have not yet injected fuel, are currently injecting fuel or have already injected fuel by means of short post-injection or correspondingly lengthening or shortening the injection timing. This achieves improved response characteristics of the engine.
Another important improvement is that in the event of one output stage failing, the engine can still continue operation on the remaining cylinders to the nearest BMW service workshop.

Cold start

Fuel injection during engine start has been improved in order to achieve more effective starting characteristics.
During engine start, a quantity of fuel is pre-injected at an engine speed > 20 rpm. This quantity is dependent on the engine coolant temperature. This ensures fuel is applied to the intake duct and inlet valves.
Renewed pre-injection after turning off the engine only takes place if the engine was running for at least 20 seconds.

Specifically MS42 / MS43

The fuel injectors are designed as two-hole fuel injectors.
This type of fuel injector is necessary because of the web arranged between both intake valves. The same quantity of fuel is injected at both fuel injectors in order to achieve improved mixture preparation. This requirement is ensured by the new design of the fuel injectors.