BMW N55, Manual, Page: 97 / 100

97
N55 Engine
Hot-film air mass meter
The Siemens SIMAF GT2 hot-film air mass meter is used. This sensor is equipped with
planar metal resistors on glass. Based on the tried and tested sensor technology used in
the SIMAF GT1 for more than 15 years, the SIMAF GT2 represents a further-develop-
ment and optimization with higher vibration resistance, improved accuracy (at all operating
temperatures), and lower sensitivity to air pulsations and water.
High Pressure Fuel Injector Valve
The HDEV5.2 solenoid type injector valves used on the N55 engine are a new
development.
1 Booster phase :
Opening of the HDEV5.2 is initiated in the booster phase by a high booster voltage
from the DME. The booster phase ends on reaching approximately 10 amps.
The high current is achieved by a voltage of up to approximately 65 Volt.
2 Energizing phase :
In the energizing phase, the HDEV5.2 is completely opened by controlling the
current to approximately 6.2 amps. At the end of the energizing phase, the current is
reduced to the holding current level of approximately 2.5 amps.
3 Hold phase:
The energized HDEV5.2 is kept open by controlling the current at approximately
2.5 amps in the hold phase.
4 Switch off phase:
The current is switched off at the end of the injection time (in the switch off phase).
At least 2 milliseconds elapse between two injection cycles.
Hot-film air mass meter