Diode Trick Alternative: Best Options & Reviews

Hello everyone,

Has anyone here ever tried reducing the heating voltage (i.e., the 12V)?
In this case, the measuring wire is colder, which results in a lower voltage drop of the 5V supply, leading the Mass Air Flow (MAF) sensor to assume a higher air mass.
This results in a consistently higher mass airflow (MAF) value across the entire RPM range, whereas the 'Holzhammer' method – using a diode trick – produces the maximum value at low RPMs, and potentially a lower value at high RPMs, depending on the diode used.

Best regards,
Matthias.

Hello!

You probably aren't familiar with the measurement principle of HFM.

The heating surface is maintained at a constant temperature, regardless of the supply voltage. This voltage can drop to approximately 8V.
If it gets any smaller, the temperature cannot be maintained.

Due to the measurement principle of the HFM, measurement errors occur that report a TOO LOW air mass. At 6V, this error is already -50% of the value at 12V.

Since the temperature difference measured by each temperature sensor, located upstream and downstream of the heating element (in the direction of flow), serves as the basis for the signal, this behavior is easily understandable.

Similarly, the older wire sensors cannot be modified in this way. In this case as well, the wire is maintained at a constant temperature. The amount of heating power required is a direct measure of the air mass.

Apart from that, such a redesign would not change the fundamental problem of the old HFM: its susceptibility to contamination, especially by water and oil mist.

BYE
TDI mechanics.