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 preparation means that the fuel-air 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)
Responds to changes in load by correcting the injection duration specifically for the individual cylinder (during the intake stroke the injection duration can be corrected with a supplementary post-injection discharge as well as by extending or reducing the injection period)
Selective deactivation of individual cylinders is also available (for instance, in response to a defective ignition coil)
Allows individual diagnosis of each fuel injector.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

High-Pressure Fuel System (N55): Notes

Use the Manual With the Right Hardware

When to See a Mechanic