Hi all,

As the title says I am working on a HFM2 to HFM5 maf conversion in a M3.8.3 ecu PN 06A906018CG for a 1.8t DBC. Found out that early VR5 engines came out with M3.8.3 ecu (071906018) and HFM5 2,75" maf from the factory, so we have a OEM starting point to make the conversion.

I first made the pinout and new connector (already covered on other posts in the forum, wiring is ok with 12v, extra 5v pin added, ground, and info), so this is correct.

Then copied the original MAF curve from VR5 ecu to 1.8t ecu and started the engine, but it ran badly.

I suspect there are other things to be copied from original VR5 map like KHFM and MLOFS (MLOFS for sure, FR says to use MLOFS 0 for HFM2 and MLOFS 200 for HFM5), but I belive KHFM will mess up load values and timing, so maybe only MLOFS is needed?

Is there anybody with experience in this? Just asking before trying to run it again because in my M3.8.2/3 damos MLOFS is not listed and I have to guess it's location based on deduction, and I don't want it to not run properly and not know if it's because I need more tweaking or because the MLOFS location deduction is not correct.

I believe MLOFS is in 0646A in the ori file I uploaded as I have seen in a VR6 M3.8.1 file that MLOFS is quite near KHFM. Anybody can confirm?

Thank you so much for your time.

Best regards,

Hi Gremlin, thank you for having a look at it. I belive we may not have the same address for KHFM because in my case, 07387, i have no zeros around it. Also I do not have a DAMOS or map pack for 071906018, so my KHFM is an assumption too.

I have deducted that a value of 200 in hex may look like C8 00 from changing the value 0 to 200 in MLOFS map in the VR6 M3.8.1 damos, so looking in the VR5 file for C8 00 I have found the first one seen in the picture, but sincerely, I am not sure it may be correct...

I am a bit lost on this, does anybody have a bit more insight?

Thank you so much

Best regards

Gremlin you are very right, I had the assumption but you confirmed it. It is curious because M3.8.1 damos, MLOFS is present and has value 0, and offset in MLHFM map is 0 too. But in M3.8.2 there is no MLOFS in damos but offset is -200 in MLHFM although the sensor is HFM2, just like the 071906018 software we are looking at that has HFM5 sensor.

So, once we know we do not need to touch MLOFS and I have the HFM5 MLHFM data copied into the 1.8t file:

- I suppose I need to adapt KHFM from the VR5 bin to the 1.8t, correct?  Will I need to redo any maps? Or load values will be correct for the new MAF with its KHFM?

- Using stock 1.8t injectors may I need to adapt FGAT0 too?

My idea is to be able to use the HFM5 on a stock setup as a base. Only with MLHFM the setup ran very very rich and lumpy.

Thank you so much for your input, I really, really appreciate it.

Best regards!

Hello all

New approach to this topic:

With the swap to VR5 / PD130 MAF we were trying to implement two changes at the same time: MAF type (from HFM2 to HFM5) and diameter increase (from 2,5" to 2,75"). So I had the idea to go one step at the time to try and diagnose if the my problems were caused by the maf type change or the diameter change.

So I did the test with a good known 2,5" HFM5 maf from a ME7 1.8t from a collegue's car. Converted MLHFM from 512x1 to 256x1 and put the map in ecu, and the car idled as bad as with the VR5 MAF. So problem seems to come from the maf type change.

I remembered people mentioned they deleted the negative readings from the map (which I didn't trying to see if it worked out of the box, as remember, VR5 uses HFM5 MAF with M3.8.3 ecu and this has negative values in it), but so did I zeroed those values and the car now runs much better but still slowly goes back to stumbling... But it's some progress   by only changing MLHFM and zeroing negative values. Both 1.8T and VR5 HFM5 mafs are having the same behaviour and both MAFs are sending to the ecu the correct signal voltage to the air it is flowing, checked with multimeter and VCDS. So I think we may be on the right track.

I have seen PRJ list the maps he changed to adapt HFM5 from R32/Phaeton to M3.8.3, but he also adapted other injectors at the same time and the list is a big mix. Here it is for reference: http://nefariousmotorsports.com/forum/index.php?topic=21532.0title=

FGAT0
MLST
MLHFM
KLWF
KFMLDMX
KFLF
Cold start cranking map. IDK the name found in ASM.
TVUB
KFBAKL
KFVAKL
ABAKN
FBAWN
FVAWN

I believe the only maps related to the MAF are MLHFM and MLST, but MLST being only the initial MAF reading for startup I consider it may not be involved afterwards... I have gone through M3.8.3 damos and FR and haven't been able to see anything else that may need tweaking.

We would be very appreciated if anybody with some experience or knowledge could chime in and give us a hint on what to look at or consider relevant to keep moving forward. I belive this to be an interesting topic to all of us with AEBs, AGUs, VR6s, with the old style mafs which are stupidly expensive and hard to find, to be able to switch over to a more modern and cheaper (but yet Bosch original) component.

As always, thank you all in advance.

Best regards

Hi mate, thanks for joining the topic. I know you made it work, but from your explanations about the file, which I admit it was some hard work you did there, seems based a bit on trial/error. And in the M3.8.3 FR it is actually considered the option to use an HFM5 MAF like it came from the factory by only changing MLHFM    But clearly isn't working hah   

The reason to try to make it work is because there is no way of fitting the big maf from the phaeton in the stock A4 B5 airbox, and to make it work with the stock injectors and don't have the need to use de 440cc units.

The intention is to have a modern and correctly priced maf to use with these cars and keep them on the road whether they are stock or tuned.

I really appreciate you made the file available on your website, but I am not sure it'll help understand how to make this work. Actually the problem we're having is the car runs goodish for about 10 seconds and then slowly starts to go lean and stumble... If I blip the throttle goes to idle fine again and after 10 seconds goes lean again... I know an emulator will help with this, after summer I'm getting one, but in the meantime I thought was a good idea to keep on working and sharing the progress.

Hope you can give a bit more input, your experience and knowledge is very valuable 

Best regards