Fuel injection: Notes

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The N55 6-cylinder spark-ignition engine relies on direct fuel injection. The direct fuel injection increases the performance. The maximum fuel pressure is 200 bar (idle: 50 bar, WOT full load: 200 bar). The use of direct fuel injection creates a homogeneous mixture preparation in the entire combustion chamber. Homogeneous mixture formation means that the air/fuel ratio is regulated stoichiometrically in the same way as for intake pipe fuel injection (Lambda = 1). A stoichiometric air-fuel mixture contains a ratio of 14.7 kilograms of air to 1 kilogram of fuel. Homogeneous mixture formation renders it possible to use a conventional emissions control system. Fully-sequential multipoint injection with selective control for each individual cylinder offers the following advantages:

Optimal fuel mixtures for each individual cylinder
The injection duration is precisely adapted to the engine's instantaneous operating conditions (engine speed, load factor and temperature)
For varying load, cylinder-specific correction of fuel injection (during an intake stroke, the injection period can be corrected by extending or shortening it through subsequent fuel injection)
Selective deactivation of individual cylinders is also available (for instance, in response to a defective ignition coil)
Allows individual diagnosis of each fuel injector.