Boxster (986) F6-2.5L (1998)
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This mass air flow sensor, also described as a micro-mechanical hot film mass air flow sensor on account of its size, is inserted into the air filter housing
at the outlet of the air filter.
Like the previous HFM, the new HFM 5 is also immune to dirt. After 100,000 miles, the characteristics deviation for the HFM 5 is thus less than 3%
resulting from dirt deposits forming on the hot-film element The operating voltage range is 9 - 17 Volts. The output voltage of the mass air flow sensor
(the voltage to the DME control unit) is between 0 - 5 Volts.
Apart from the power which the on-board voltage supply provides for the mass air flow sensor, the actual measuring element is supplied with a regulated
voltage of 5 Volts from the control unit so that fluctuations in the on- board voltage supply, e.g. caused by switching on the consumers, do not have an
effect on the measuring process.
Deviations from the supply voltage are thus also included in calculation of the mass air flow performed by the DME control unit. As a result, there are no
negative effects on the determination of mass air flow since the control unit calculates the relationship between the supplied supply voltage and the
output voltage of the mass air flow sensor.
Air Flow Through Measuring Element:
