MAF
MAF Tuner - This program will automatically compile several short datalogs and calculate a resultant Tuned MAF curve.
MAF Tuning (thanks to ba114 for thread and spreadsheet attached below)
BMW uses a MAF sensor with a 12V input and 0-5V output. The transfer function correlates to a 3rd or 5th order polynomial like most MAF sensor outputs. ECU can read Airflow up to 1024 kg/hr with the stock software limits. However, this can be increased to 2048 kg/hr by modifying the 256KB binary.
Caution for Turbochargers
If you run this with a Turbocharger that spools up quickly, you will overflow the Load variable in the 2500 to 3500RPM range since Load/Torque builds too quickly for the stock ECU code to handle and will result in extremely lean AFRs and engine damage.
Datalog and make sure you are not getting close to the 1389 Load (mg/stroke) limit.
If you are, delay the onset of boost a little bit.
Superchargers and NA tunes are OK to use with this.
Load limit is always 1389 mg/stroke.
This modification allows the ECU to handle up to 700 BHP worth of air. The tables are now shown in 16x16 format instead of 256x1 so it's easier to select all cells for editing. Once 2048 kg/hr Mode is activated, the corresponding MAF Scaling table in 2048 kg/hr Mode must be modified to display the correct values prior to the next reflash attempt. This usually means dividing all 256 cells by 2 if coming from stock values.
In this example, we want to multiply the MAF limit by 2 by selecting 2048 kg/hr Mode so we must divide all the 256 cells by 2 to maintain same Engine operation as before.
The MAF Scaling for 1024 kg/hr Mode is 'read-only' for MS41.2 and MS41.1 due to a software limitation with RomRaider. If you choose to modify your MAF Scaling but not select 2048kg/hr mode, understand this 2x multiplier.
Alternatively, you can MOVE the following section in the definition XML file to come BEFORE the table you want to use to edit the MAF.
MAF Sensors
Stock = 725kg/hr
Porsche 993 803 MAF = 1237kg/hr?
BMW 540i 800 MAF = 843kg/hr?
Euro M3 806 MAF = 834kg/hr?
Nissan = various?
HPX = various?
Ford = various?
Good thread on the differences between the Porsche, Euro M3, and 540i MAF.
History
'Original' Thread (2007) - https://forums.nasioc.com/forums/showthread.php?t=1363692
This MAF / Load 'hack' obviously originated from the very first ECU, since that is the only way to do it in the firmware. Just depends on your overall scaling/resolution desired while modeling to discrete 16-bit binary data from continuous real world airflow. it's just funny to see different people over the years 're-discover' it like we did back in 2007
'Child' Thread (2008) - https://forums.nasioc.com/forums/showthread.php?t=1811129
I guess this concept was originally only understood by the intellectual elites after the first explanation. So, it had to be repeated for people a slightly different way.
'Another' Thread (2012) - https://www.clubwrx.net/threads/maf-hack-questions.134361026/
LOL. I guess some people can't be bothered to read the first post of a thread.