Hey tuning-folks,

I have a couple of questions considering an HFM 2 to HFM 5 conversion on my Audi A4 B5 with a 1.8T (AEB) with an M3.8.2 ECU (0261204805). The car is running a K04-15 upgrade turbocharger and is maxing out the orignal HFM and injectors.

First step therefore is to get an HFM running, which can read more airmass than the original one. I already made an adapter harness for an HFM5 from the 1.8T BFB as a first test, because this sensor neatly fits in the original airbox. The new HFM is up and running smoothly...

Currently me and my tuner are running into a couple of issues that one of you may have already encountered with the original M3.8.2 ECU and maybe found a solution for.

1.) The characteristic curve for airflow mass for the new HFM5 uses the physical value of output voltage PIN 5 (0V to 5V) as a reference on the x-Axis, whereas the old HFM2 uses an LSB counter (0 to 255) on the x-Axis. Has anyone got a conversion table for the exact voltages to bit values? 0V=0 and 5V=255 with equidistant spacing inbetween seems to be off by a bit...

2.) The newer HFM5 seems to suffer from a bigger dead time than the old one, which leeds to the car running quite lean briefly while accelerating. What would be the best way to avoid running into the lean combustion with the newer HFM?

Thanks for any help. Best Regards

-Johannes

On second notice while I was looking at the HFM datasheet, I found out that the dead time of the newer HFM5 should be equal or lower than the older one. So if the correct characteristic curve was loaded into the respective ECU-table, there shouldn't be a temporary lean mixture at all - right?

Ich denke, Sie sollten das HFM5 anschließen und mach ein paar logs mit VCDs und von dort aus die Airmas-Tabelle anpassen und prüfen Sie, ob es reagiert